Chris Fogelklou
Introduction:
This is a demonstration of a Scenix SX microcontroller performing frequency detection on an analog signal. The user selects a frequency, and the SX determines the amount of the selected frequency present in the input signal. The magnitude of the signal is then output to the terminal in a "level-meter" display. Several Virtual Peripherals are utilized for this application:
The Detection Algorithm
In this interpretation of the Goertzel Algorithm, we utilize a 1-bit Sigma-Delta Analog to Digital converter. Most DSP algorithms require the processor to store hundreds of values and post-process them. Since this Scenix algorithm processes the incoming signal as it is sampled, RAM usage is tiny and the processing required after a sampling period is minimized. Also, because the analog to digital conversion is only a 1-bit conversion, only an add- or subtract-function is executed on each sample. Over a period of time, the result is the same as multiplying a multi-bit sample by a coefficient and accumulating the results, but the multiplication process is eliminated. Though each sample is of 1-bit resolution, the overall resolution is good because the input signal is oversampled. (400x oversampling on a 1kHz input signal.)
Vin (2.5VDC +/- Signal)
The hardware required to perform frequency detection on an SX consists of only two I/O pins of the SX, 2 resistors, and a capacitor.
C1
A sine and a cosine reference wave are generated at the frequency to be detected. Each 1-bit A/D sample determines whether or not to add or subtract the value of each reference wave from its respective sine accumulator or cosine accumulator,
After a period of time has passed (20ms), the value stored in these accumulators indicates the amount of the detected frequency present in the signal. To determine the amount of the selected frequency detected in the signal, this calculation is used:
Frequency Magnitude = (accumulated sine result2 + accumulated cosine result2) -2
The result of this calculation is normalized and output to the terminal screen in a "level-meter" format.
Some possible applications of this algorithm are:
1 of 1
;****************************************************************************** ; Copyright © [04/22/1999] Scenix Semiconductor, Inc. All rights reserved. ; ; Scenix Semiconductor, Inc. assumes no responsibility or liability for ; the use of this [product, application, software, any of these products]. ; Scenix Semiconductor conveys no license, implicitly or otherwise, under ; any intellectual property rights. ; Information contained in this publication regarding (e.g.: application, ; implementation) and the like is intended through suggestion only and may ; be superseded by updates. Scenix Semiconductor makes no representation ; or warranties with respect to the accuracy or use of these information, ; or infringement of patents arising from such use or otherwise. ;****************************************************************************** ; Filename: Freq_Det_1_03.src ; ; Authors: Chris Fogelklou ; Applications Engineer ; Scenix Semiconductor,Inc ; ; Revision: 1.03 ; ; Part: SX28AC datecode 9929AA ; Freq: 50Mhz ; Compiled using Parallax SX-Key software v1.07 and SASM 1.40 ; ; Date Written: 04/22/1999 ; ; Last Revised: 10/20/1999 ; ; Program Description: ; This program demonstrates the use of a correlation algorithm ; to calculate how similar an incoming frequency is to a frequency ; input by the user. It uses a sigma-delta A/D in conjunction with ; simple arithmetic to accumulate the filter output. ; ; This program is compatible with the SX-Demo board, but some values need to ; be modified to run the sigma-delta A/D converter. R12 should be 10k, ; R11 should be 22k, and C7 should be 1000pF. These values gave excellent ; results when used with a function generator. For best results, set the output ; of the function generator to 2.5VDC with an output swing of about 0.8V. ; For a more sensitive A/D, Decrease the value of R11, while increasing the value ; of R12. ; ; ; R12 R11 ; 10k 22k ; RC0-----\/\/----x-------\/\/------>Vin (2.5V +/- 0.8V) ; | ; RC1-------------x ; | ; ----- C7 ; ----- 1000pF ; | ; O ; VSS ; ; ; SCREENSHOT: ; ; SX Frequency Detector ; Enter a frequency in Hz: 1000 ; Press any key to escape ; LEVEL:***************************************************** > ; ; This program runs on the Parallax SX-Demo board. ; It uses a baud rate which is chosen by uncommenting the appropriate baud rate defines below: ; ; 19200 baud (sample rate /16) ; baud_bit = 4 ;for 19200 baud ; start_delay = 16+8+1 ; " " " ; int_period = 163 ; " " " ; 38400 baud (sample rate /8) ; baud_bit = 3 ;for 38400 baud ; start_delay = 8+4+1 ; " " " ; int_period = 163 ; " " " ; 57600 baud (sample rate /8) ; baud_bit = 3 ;for 57600 baud ; start_delay = 8+4+1 ; " " " ; int_period = 109 ; " " " ; 115.2kbaud (sample rate /4) baud_bit = 2 ;for 115200 baud start_delay = 4+2+1 ; " " " int_period = 109 ; " " " ; ; Length: 731 words ; Version: 1.02 ; Revision History ; 1.0 Initial program written. ; 1.01 Some formatting and documentation changed, as well as some subroutines ; such as delay_n_ms. ; 1.02 Re-documented for use with SASM and SX-52 ; Re-wrote some of the routines for compatibility with ; SX-52. ; 1.03 Removed CARRYX directive and modified code accordingly ;****************************************************************************** ;***************************************************************************************** ; Target SX ; Uncomment one of the following lines to choose the SX18AC, SX20AC, SX28AC, SX48BD/ES, ; SX48BD, SX52BD/ES or SX52BD. For SX48BD/ES and SX52BD/ES, uncomment both defines, ; SX48_52 and SX48_52_ES. ;***************************************************************************************** ;SX18_20 SX28 ;SX48_52 ;SX48_52_ES ;***************************************************************************************** ; Assembler Used ; Uncomment the following line if using the Parallax SX-Key assembler. SASM assembler ; enabled by default. ;***************************************************************************************** SX_Key ;********************************************************************************* ; Assembler directives: ; high speed external osc, turbo mode, 8-level stack, and extended option reg. ; ; SX18/20/28 - 4 pages of program memory and 8 banks of RAM enabled by default. ; SX48/52 - 8 pages of program memory and 16 banks of RAM enabled by default. ; ;********************************************************************************* IFDEF SX_Key ;SX-Key Directives IFDEF SX18_20 ;SX18AC or SX20AC device directives for SX-Key device SX18L,oscxt4,turbo,stackx_optionx,carryx ENDIF IFDEF SX28 ;SX28AC device directives for SX-Key device SX28L,oscxt4,turbo,stackx_optionx,carryx ENDIF IFDEF SX48_52_ES ;SX48BD/ES or SX52BD/ES device directives for SX-Key device oschs,turbo,stackx,optionx,carryx ELSE IFDEF SX48_52 ;SX48/52/BD device directives for SX-Key device oschs2,stackx_optionx,carryx ENDIF ENDIF freq 50_000_000 ELSE ;SASM Directives IFDEF SX18_20 ;SX18AC or SX20AC device directives for SASM device SX18,oschs2,turbo,stackx,optionx,carryx ENDIF IFDEF SX28 ;SX28AC device directives for SASM device SX28,oschs2,turbo,stackx,optionx,carryx ENDIF IFDEF SX48_52_ES ;SX48BD/ES or SX52BD/ES device directives for SASM device SX52,oschs,turbo,stackx,optionx,carryx ELSE IFDEF SX48_52 ;SX48BD or SX52BD device directives for SASM device SX52,oschs2,stackx,optionx,carryx ENDIF ENDIF ENDIF id 'DFT1_02 ' ; reset reset_entry ; JUMP to start label on reset ;***************************************************************************************** ; Macros ;***************************************************************************************** ;********************************************************************************* ; Macro: _bank ; Sets the bank appropriately for all revisions of SX. ; ; This is required since the bank instruction has only a 3-bit operand, it cannot ; be used to access all 16 banks of the SX48/52. For this reason FSR.4 (for SX48/52BD/ES) ; or FSR.7 (SX48/52bd production release) needs to be set appropriately, depending ; on the bank address being accessed. This macro fixes this. ; ; So, instead of using the bank instruction to switch between banks, use _bank instead. ; ;********************************************************************************* _bank macro 1 bank 1円 IFDEF SX48_52 IFDEF SX48_52_ES IF 1円 & %00010000 ;SX48BD/ES and SX52BD/ES (engineering sample) bank instruction setb fsr.4 ;modifies FSR bits 5,6 and 7. FSR.4 needs to be set by software. ENDIF ELSE IF 1円 & %10000000 ;SX48BD and SX52BD (production release) bank instruction setb fsr.7 ;modifies FSR bits 4,5 and 6. FSR.7 needs to be set by software. ELSE clrb fsr.7 ENDIF ENDIF ENDIF endm ;********************************************************************************* ; Macro: _mode ; Sets the MODE register appropriately for all revisions of SX. ; ; This is required since the MODE (or MOV M,#) instruction has only a 4-bit operand. ; The SX18/20/28AC use only 4 bits of the MODE register, however the SX48/52BD have ; the added ability of reading or writing some of the MODE registers, and therefore use ; 5-bits of the MODE register. The MOV M,W instruction modifies all 8-bits of the ; MODE register, so this instruction must be used on the SX48/52BD to make sure the MODE ; register is written with the correct value. This macro fixes this. ; ; So, instead of using the MODE or MOV M,# instructions to load the M register, use ; _mode instead. ; ;********************************************************************************* _mode macro 1 IFDEF SX48_52 mov w,#1円 ;loads the M register correctly for the SX48BD and SX52BD mov m,w ELSE mov m,#1円 ;loads the M register correctly for the SX18AC, SX20AC ;and SX28AC ENDIF endm ;***************************************************************************************** ; Data Memory address definitions ; These definitions ensure the proper address is used for banks 0 - 7 for 2K SX devices ; (SX18/20/28) and 4K SX devices (SX48/52). ;***************************************************************************************** IFDEF SX48_52 global_org = 0ドルA bank0_org = 00ドル bank1_org = 10ドル bank2_org = 20ドル bank3_org = 30ドル bank4_org = 40ドル bank5_org = 50ドル bank6_org = 60ドル bank7_org = 70ドル ELSE global_org = 08ドル bank0_org = 10ドル bank1_org = 30ドル bank2_org = 50ドル bank3_org = 70ドル bank4_org = 90ドル bank5_org = $B0 bank6_org = $D0 bank7_org = $F0 ENDIF ;***************************************************************************************** ; Global Register definitions ; NOTE: Global data memory starts at 0ドルA on SX48/52 and 08ドル on SX18/20/28. ;***************************************************************************************** org global_org temp equ global_org ; Temporary storage register temp2 equ global_org+1 flags equ global_org+2 freq_det_en equ flags.0 timer_flag equ flags.1 rx_flag equ flags.2 loopcount equ global_org+3 isr_temp equ global_org+4 ;***************************************************************************************** ; RAM Bank Register definitions ;***************************************************************************************** ;********************************************************************************* ; Bank 0 ;********************************************************************************* org bank0_org bank0 = $ timers = $ timer_l ds 1 timer_m ds 1 timer_h ds 1 sine_gen_bank = $ freq_acc_l ds 1 freq_acc_h ds 1 freq_count_l ds 1 freq_count_h ds 1 ;********************************************************************************* ; Bank 1 ;********************************************************************************* org bank1_org bank1 = $ freq_det_bank = $ sine_index ds 1 sine_value ds 1 cose_value ds 1 sine_acc_l ds 1 sine_acc_h ds 1 cose_acc_l ds 1 cose_acc_h ds 1 math_bank = $ answer_l ds 1 answer_h ds 1 input ds 1 input2 ds 1 loop_count ds 1 math_flags ds 1 neg equ math_flags.0 root_mask ds 1 ;********************************************************************************* ; Bank 2 ;********************************************************************************* org bank2_org bank2 = $ serial = $ ;UART bank tx_high ds 1 ;hi byte to transmit tx_low ds 1 ;low byte to transmit tx_count ds 1 ;number of bits sent tx_divide ds 1 ;xmit timing (/16) counter rx_count ds 1 ;number of bits received rx_divide ds 1 ;receive timing counter rx_byte ds 1 ;buffer for incoming byte string ds 1 byte ds 1 dec_l ds 1 ;Holds the 16-bit value returned dec_h ds 1 ;from get_dec subroutine. ;********************************************************************************* ; Bank 3 ;********************************************************************************* org bank3_org bank3 = $ ;********************************************************************************* ; Bank 4 ;********************************************************************************* org bank4_org bank4 = $ ;********************************************************************************* ; Bank 5 ;********************************************************************************* org bank5_org bank5 = $ ;********************************************************************************* ; Bank 6 ;********************************************************************************* org bank6_org bank6 = $ ;********************************************************************************* ; Bank 7 ;********************************************************************************* org bank7_org bank7 = $ IFDEF SX48_52 ;********************************************************************************* ; Bank 8 ;********************************************************************************* org 80ドル ;bank 8 address on SX52 bank8 = $ ;********************************************************************************* ; Bank 9 ;********************************************************************************* org 90ドル ;bank 9 address on SX52 bank9 = $ ;********************************************************************************* ; Bank A ;********************************************************************************* org $A0 ;bank A address on SX52 bankA = $ ;********************************************************************************* ; Bank B ;********************************************************************************* org $B0 ;bank B address on SX52 bankB = $ ;********************************************************************************* ; Bank C ;********************************************************************************* org $C0 ;bank C address on SX52 bankC = $ ;********************************************************************************* ; Bank D ;********************************************************************************* org $D0 ;bank D address on SX52 bankD = $ ;********************************************************************************* ; Bank E ;********************************************************************************* org $E0 ;bank E address on SX52 bankE = $ ;********************************************************************************* ; Bank F ;********************************************************************************* org $F0 ;bank F address on SX52 bankF = $ ENDIF ;***************************************************************************************** ; Port Assignment ;***************************************************************************************** RA_init equ %11111111 ;SX18/20/28/48/52 port A latch init RA_io equ %11110111 ;SX18/20/28/48/52 port A DDIR value RA_plp equ %11111100 ;SX18/20/28/48/52 port A PLP value (pullups) RA_cmos equ %00000000 ;SX18/20/28/48/52 port A LVL value RB_init equ %11111111 ;SX18/20/28/48/52 port B latch init RB_io equ %11111111 ;SX18/20/28/48/52 port B DDIR value RB_cmos equ %00000000 ;SX18/20/28/48/52 port B LVL value RC_init equ %00000000 ;SX18/20/28/48/52 port C latch init RC_io equ %11111110 ;SX18/20/28/48/52 port C DDIR value RC_cmos equ %00000000 ;SX18/20/28/48/52 port C LVL value IFDEF SX48_52 RD_init equ %11111111 ;SX48/52 port D latch init RD_io equ %11111111 ;SX48/52 port D DDIR value RD_cmos equ %00000000 ;SX18/20/28/48/52 port D LVL value RE_init equ %11111111 ;SX48/52 port E latch init RE_io equ %11111111 ;SX48/52 port E DDIR value RE_cmos equ %00000000 ;SX18/20/28/48/52 port E LVL value ENDIF ;************************************************************************** ; Pin Definitions ;************************************************************************** rx_pin EQU ra.2 ;UART receive input tx_pin EQU ra.3 ;UART transmit output ;************************************************************************** ;************************************************************************** ;************************************************************************** ; START OF PROGRAM MEMORY HERE!!! org 0 ;************************************************************************** ; Interrupt... This interrupt routine has two different vectors with two seperate ; interrupt rates. As a result, the UART MUST be finished sending ; before the rates are switched. This is why the send_byte routine ; was changed to not exit until the entire byte has been sent. ;************************************************************************** mov w,>>rc ;1 ; Perform negative feedback on input not w ;1 ; signal. Continue even when DFT is not mov rc,w ;1 ; running, to keep input at 2.5V DC snb freq_det_en ;1 ; IF frequency detection is enabled, go jmp @SINE_DETECTION ;3 ; to the frequency detection ISR instead. ;-------------------------------------------------------------------------- :transmit ; This is an asynchronous transmitter for RS-232 transmission ; INPUTS: ; divider.divider_bit - Transmitter/receiver only executes when this bit is = 1 ; tx_divide.baud_bit - Transmitter only executes when this bit is = 1 ; tx_high - Part of the data to be transmitted ; tx_low - Some more of the data to be transmitted ; tx_count - Counter which counts the number of bits transmitted. ; OUTPUTS: ; tx_pin - Sets/Clears this pin to accomplish the transmission. ;-------------------------------------------------------------------------- bank serial clrb tx_divide.baud_bit ;clear xmit timing count flag inc tx_divide ;only execute the transmit routine STZ ;set zero flag for test SNB tx_divide.baud_bit ; every 2^baud_bit interrupt test tx_count ;are we sending? JZ :receive ;if not, go to :receive clc ;yes, ready stop bit rr tx_high ; and shift to next bit rr tx_low ; dec tx_count ;decrement bit counter movb tx_pin,/tx_low.6 ;output next bit ;-------------------------------------------------------------------------- :receive ; This is an asynchronous receiver for RS-232 reception ; INPUTS: ; rx_pin - Pin which RS-232 is received on. ; OUTPUTS: ; rx_byte - The byte received ; rx_flag - Set when a byte is received. ;-------------------------------------------------------------------------- movb c,rx_pin ;get current rx bit test rx_count ;currently receiving byte? jnz :rxbit ;if so, jump ahead mov w,#9 ;in case start, ready 9 bits sc ;skip ahead if not start bit mov rx_count,w ;it is, so renew bit count mov rx_divide,#start_delay ;ready 1.5 bit periods :rxbit djnz rx_divide,:rxdone ;middle of next bit? setb rx_divide.baud_bit ;yes, ready 1 bit period dec rx_count ;last bit? sz ;if not rr rx_byte ; then save bit snz ;if so setb rx_flag ; then set flag :rxdone ;****************************************************************************** :ISR_DONE ;****************************************************************************** mov w,#-int_period ;1 ; interrupt (int_period) cycles from the start of this interrupt. retiw ;3 ; return from the interrupt ;************************************************************************** ; This is the end of the interrupt service routine for the UARTs ;************************************************************************** ; This is the beginning of the interrupt service routine for the Frequency detection ;************************************************************************** ;-------------------------------------------------------------------------- sine_table ;7 cycles ; Returns with the value at (w) in (w) ; This entire table MUST be located in the first half of the page ; from which it is called. ;-------------------------------------------------------------------------- ; Returns the sine value at index. clc ;1 jmp pc+w ;3,3 retw 0 retw 3 retw 6 retw 8 retw 11 retw 12 retw 14 retw 15 retw 15 retw 15 retw 14 retw 12 retw 11 retw 8 retw 6 retw 3 retw 0 retw -3 retw -6 retw -8 retw -11 retw -12 retw -14 retw -15 retw -15 retw -15 retw -14 retw -12 retw -11 retw -8 retw -6 retw -3 jmp $ ;-------------------------------------------------------------------------- SINE_DETECTION ;4 ; Part of the interrupt service routine!!! This routine adds or ; subtracts the values of the sine and cose references from their ; corresponding accumulators, depending on whether or not the input ; matches or does not match the reference. ;-------------------------------------------------------------------------- bank sine_gen_bank ;1 clr isr_temp add freq_acc_h,freq_count_h ;2 ; and cose references, this addition snc setb isr_temp.0 add freq_acc_l,freq_count_l ;2 ; If it is time to update the sine snc inc freq_acc_h test freq_acc_h jnz :no_update ;1 15 jnb isr_temp.0,:no_update :update bank freq_det_bank ;1 ; OK, Carry produced. Now, update the inc sine_index ;1 ; sine and cose references. Do this mov w,sine_index ;1 ; by incrementing the index into the table. and w,#1ドルf ;1 call sine_table ;7 26 ; and get the value at (index) mov sine_value,w ;1 ; store the new sine reference value mov w,#8 ;1 ; Now get the cose reference value. Add 8 add w,sine_index ;1 ; to the sine index and get the value at and w,#1ドルf ;1 ; this location. call sine_table ;7 mov cose_value,w ;1 38 ; store the new cose reference value. :no_update bank freq_det_bank ;1 ; Perform the DFT calculations. If the do_sine_ref ; negative feedback pin is positive, add mov w,sine_value ;1 ; the reference, otherwise subtract it. sb rc.0 ;1 jmp :add_reference ;3 :sub_reference stc ;1 43 ; Signed 16-bit subtraction of 8-bit reference sub sine_acc_l,w ;1 clr w ;1 snb sine_value.7 ;1 not w ;1 sub sine_acc_h,w ;1 jmp do_cose_ref ;3 49 :add_reference clc ;1 44 ; Signed 16-bit addition of 8-bit reference add sine_acc_l,w ;1 clr w ;1 snb sine_value.7 ;1 not w ;1 add sine_acc_h,w ;1 50 do_cose_ref mov w,cose_value ;1 52 ; Now do the same calculations for the cose sb rc.0 ;1 ; reference. jmp :add_reference ;3,1 :sub_reference stc ;1 55 ; Signed 16-bit subtraction of 8-bit reference sub cose_acc_l,w ;1 clr w ;1 snb cose_value.7 ;1 not w ;1 sub cose_acc_h,w ;1 jmp DFT_DONE ;3 63 :add_reference clc ;1 56 ; Signed 16-bit addition of 8-bit reference add cose_acc_l,w ;1 clr w ;1 snb cose_value.7 ;1 not w ;1 add cose_acc_h,w ;1 64 DFT_DONE ; 65 do_nothing sb rx_pin ; If the rx_pin goes low, set a flag to indicate setb rx_flag ; it is time to reset the program. (User has pushed a key.) ;-------------------------------------------------------------------------- do_timers bank timers ; 16-bit timer for delay_n_ms routine. These timers tick at ; a rate of (interrupt rate * 20ns) = 2.38us = 420.168 kHz inc timer_l snz inc timer_h snz setb timer_flag ;************************************************************************** ; End of the ISR for the Frequency detection algorithm. ;************************************************************************** mov w,#-119 ; Return value for easy DFT constants. (frequency * 5) retiw ;************************************************************************** ; END OF THE INTERRUPT SERVICE ROUTINES!!! ;************************************************************************** ;************************************************************************** ;************************************************************************** org 1ドルfe ;****************************************************************************************** reset_entry ; Program starts here on power-up and on reset. jmp @start ; jump to the main program. ;************************************************************************** org 200ドル ;****************************************************************************************** org 300ドル ;************************************************************************** ; String data (for RS-232 output) and tables needs to be in page 300ドル for send_string ; to work. ;************************************************************************** _hello dw 13,10,'SX Frequency Detector',0 _enter_freq dw 13,10,'Enter a frequency in Hz: ',0 _press_key dw 13,10,'Press any key to escape',13,10,0 _CR dw 13,10,0 _error dw 13,10,'ERROR: Value is too large. Must be <= 13107Hz. Press ENTER ',0 _dec_error dw 13,10,'ERROR: Value is too large. Must be <= 65535 :',0 _LEVEL dw 13,'LEVEL:',0 ;****************************************************************************************** org 400ドル ;-------------------------------------------------------------------------- delay_n_ms ; This subroutine delays 'w' milliseconds. ; This subroutine uses the TEMP register ; INPUT w - # of milliseconds to delay for. ; OUTPUT Returns after n milliseconds. ;-------------------------------------------------------------------------- mov temp,w bank timers :loop clrb timer_flag ; This loop delays for 1ms ; mov timer_h,#0ドルfe ; mov timer_l,#0ドルcd mov timer_h,#0ドルfe ; These constants are used for the 119 cycle interrupt rate. mov timer_l,#05ドルc jnb timer_flag,$ dec temp ; do it w-1 times. jnz :loop clrb timer_flag retp ;-------------------------------------------------------------------------- ; Initialization Code... ;-------------------------------------------------------------------------- init _mode 1ドルd ; CMOS Init mov !ra,#RA_cmos mov !rb,#RB_cmos mov !rc,#RC_cmos _mode 1ドルf mov ra,#RA_init ; Initialize data latches for ports mov rb,#RB_init mov rc,#RC_init ; Initialize direction registers for ports. mov !ra,#RA_io ; port A. mov !rb,#RB_io ; port B. mov !rc,#RC_io ; port C. call @zero_ram mov !option,#%00011111 ; enable rtcc interrupt and wreg, no prescaler on RTCC. retp ;-------------------------------------------------------------------------- zero_ram ; Subroutine - Zero all ram. ; INPUTS: None ; OUTPUTS: All ram locations (except special function registers) are = 0 ;-------------------------------------------------------------------------- IFDEF SX48_52 ;SX48/52 RAM clear routine mov w,#0ドルa ;reset all ram starting at 0ドルA mov fsr,w :zero_ram clr ind ;clear using indirect addressing incsz fsr ;repeat until done jmp :zero_ram _bank bank0 ;clear bank 0 registers clr 10ドル clr 11ドル clr 12ドル clr 13ドル clr 14ドル clr 15ドル clr 16ドル clr 17ドル clr 18ドル clr 19ドル clr 1ドルa clr 1ドルb clr 1ドルc clr 1ドルd clr 1ドルe clr 1ドルf ELSE ;SX18/20/28 RAM clear routine clr fsr ;reset all ram banks :zero_ram sb fsr.4 ;are we on low half of bank? setb fsr.3 ;If so, don't touch regs 0-7 clr ind ;clear using indirect addressing incsz fsr ;repeat until done jmp :zero_ram ENDIF retp ;-------------------------------------------------------------------------- SignedMultiply ; 8 * 8 Signed Multiply ; INPUTS: Multiplies input2 * input ; OUTPUTS: 16-bit Signed value in answer_l and answer_h ; (low byte and high byte, respectively) ;-------------------------------------------------------------------------- mov input2,w ;1 mov w,#$ff ;1 sb input.7 ;1 jmp :input2 ;1,3 xor input,w ;1 inc input ;1 inc loop_count ;1;7 :input2 sb input2.7 ;1 jmp :done ;1 xor input2,w ;1 inc input2 ;1 inc loop_count ;1;12 :done setb neg ;1 sb loop_count.0 ;1 clrb neg ;1 clr loop_count ;1 mov w,input2 ;1;17 call Multiply ;87;104 sb neg ;1 retp ;3 mov w,#$ff ;1 xor answer_h,w ;1 xor answer_l,w ;1 inc answer_l ;1 snz ;1 inc answer_h ;1 retp ;3;113 cycles worst case ;-------------------------------------------------------------------------- Multiply ; Multiply W by input ; INPUTS: W * input ; OUTPUTS: 16-bit output value in answer_l and answer_h ;-------------------------------------------------------------------------- setb loop_count.3 ;1 clr answer_l ;1 clr answer_h ;1 ;3 :loop clc ;1 snb input.0 ;1 add answer_h,w ;1 rr answer_h ;1 rr answer_l ;1 rr input ;1 decsz loop_count ;1 jmp :loop ;3 10=looptime (78 on exit) ; 78 + 3 = 81 retp ;3 82 + 3 = 84 ALWAYS!!! ; for 16 bit result. ;-------------------------------------------------------------------------- clear_bank ; Clears an entire bank of RAM. ; To use, first load the FSR with the starting address ; of the bank to clear. ;-------------------------------------------------------------------------- :loop clr indf inc fsr sb fsr.4 retp jmp :loop ;-------------------------------------------------------------------------- ; SQ_ROOT ; By John Keenan ; Routine to take the square root of a 16 bit unsigned number ; entry: input - low byte of number ; input2 - high byte of number ; exit: W register returns 8 bit result ;-------------------------------------------------------------------------- sq_root mov root_mask,#$c0 ; initialise root_mask mov w,#40ドル ; initialise answer :sq1 stc sub input2,w ; subtract the root develped so far sc ; restore subtraction if carry cleared jmp :sq5 :sq2 or w,root_mask ; set the current bit :sq3 nop rl input ; shift number left one position rl input2 rr root_mask ; picks up ms bit of input2 snb root_mask.7 jmp :sq6 xor w,root_mask ; append 01 to the root developed so far sc ; if the lsb of root_mask was shifted into carry, jmp :sq1 ; then we're done. Otherwise loop again stc sub input2,w ; sc retp snz snb input.7 xor w,#1 retp :sq6 snc retp clrb root_mask.7 xor w,root_mask stc sub input2,w jmp :sq2 :sq5 add input2,w ; carry=0 here jmp :sq3 ;-------------------------------------------------------------------------- ; Subroutine - Get byte via serial port and echo it back to the serial port ; INPUTS: ; -NONE ; OUTPUTS: ; -received byte in w, and byte ;-------------------------------------------------------------------------- get_byte jnb rx_flag,$ ;wait till byte is received clrb rx_flag ;reset the receive flag bank serial mov byte,rx_byte ;store byte (copy using W) ; & fall through to echo char back retp ;-------------------------------------------------------------------------- ; Subroutine - Send byte via serial port ; INPUTS: ; w - The byte to be sent via RS-232 ;-------------------------------------------------------------------------- send_byte bank serial not w ;ready bits (inverse logic) mov tx_high,w ; store data byte setb tx_low.7 ; set up start bit mov tx_count,#10 ;1 start + 8 data + 1 stop bit :wait test tx_count ;wait for not busy jnz :wait ; RETP ;leave and fix page bits ;-------------------------------------------------------------------------- ; Subroutine - Send string pointed to by address in W register ; INPUTS: ; w - The address of a null-terminated string in program ; memory ; OUTPUTS: ; outputs the string via. RS-232 ;-------------------------------------------------------------------------- send_string bank serial mov string,w ;store string address :loop mov w,string ;read next string character mov m,#3 ; with indirect addressing iread ; using the mode register mov m,#$F ;reset the mode register test w ;are we at the last char? snz ;if not=0, skip ahead RETP ;yes, leave & fix page bits call send_byte ;not 0, so send character inc string ;point to next character jmp :loop ;loop until done ;-------------------------------------------------------------------------- ; Subroutine - Make byte uppercase ; INPUTS: ; byte - The byte to be converted ;-------------------------------------------------------------------------- uppercase csae byte,#'a' ;if byte is lowercase, then skip ahead RETP sub byte,#'a'-'A' ;change byte to uppercase RETP ;leave and fix page bits ;-------------------------------------------------------------------------- ; Subroutine - Output a hex number ; INPUTS: ; w - The byte to be output ;-------------------------------------------------------------------------- send_hex mov temp,w swap wreg and w,#0ドルf call hex_table call send_byte mov w,temp and w,#0ドルf call hex_table call send_byte retp hex_table ; called by send_hex ;-------------------------------------------------------------------------- clc add pc,w retw '0' retw '1' retw '2' retw '3' retw '4' retw '5' retw '6' retw '7' retw '8' retw '9' retw 'A' retw 'B' retw 'C' retw 'D' retw 'E' retw 'F' ;-------------------------------------------------------------------------- dec_table ; called by get_dec ;-------------------------------------------------------------------------- clc add pc,w retw '0' retw '1' retw '2' retw '3' retw '4' retw '5' retw '6' retw '7' retw '8' retw '9' retw 0 retw 0 retw 0 retw 13 ; A carriage return will be valid. It will return retw 0 ; with the value of a CR in it. retw 0 ;-------------------------------------------------------------------------- get_dec ; This routine returns with an 16-bit value in dec_l and dec_h registers ; register. It accepts a decimal number from the terminal screen and ; returns when the number is within range and the user presses <return> ;-------------------------------------------------------------------------- bank serial clr dec_l clr dec_h :get_next call :get_valid_dec ; get a valid decimal number. mov w,#13 xor w,byte jz :done clc ; multiply current dec input by 10. rl dec_l rl dec_h jc :error mov temp,dec_l ; save (last number * 2) mov temp2,dec_h rl dec_l rl dec_h jc :error rl dec_l rl dec_h jc :error add dec_l,temp add dec_h,temp2 ; add ((last number * 2) + (last number * 10)) jc :error add dec_l,byte clr w add dec_h,w jc :error jmp :get_next ; Get the next valid decimal number :done retp :error mov w,#_dec_error call @send_string ; Send the error message if the decimal number ; is too long. jmp get_dec ; and start over. ;-------------------------------------------------------------------------- :get_valid_dec ; Return with a character which is a valid decimal number, ; or with a '13' in 'byte' if the user presses return. ;-------------------------------------------------------------------------- bank serial call @get_byte clr temp :loop mov w,temp call dec_table xor w,byte jz :got_it inc temp jb temp.4,:get_valid_dec jmp :loop :got_it mov w,byte call @send_byte mov byte,temp ret ;****************************************************************************************** org 600ドル ;****************************************************************************************** ; START OF MAIN PROGRAM start call @init ; Initialize all registers and ports. ;****************************************************************************************** ; Send Hello message ;****************************************************************************************** mov w,#_hello ; Send hello string. call @send_string ;****************************************************************************************** ; Get the desired 16-bit frequency value from the user. ;****************************************************************************************** mov w,#_enter_freq ; Prompt for frequency value call @send_string call @get_dec ; Get Frequency value mov temp,dec_h ; Store the input 16-bit decimal value mov temp2,dec_l ;****************************************************************************************** ; Now multiply the input frequency by 5 and load it into the freq_count registers. This ; will produce a constant which will cause the sine and cose reference generators to ; construct a sine/cose wave of the desired frequency. The value of 5 is determined by a ; number of factors, including the size of the sine lookup table, and the interrupt rate, ; which is 419.4 kHz in this application during the frequency detection. If, while multiplying ; the input frequency by 5, the result exceeds 16-bits, output an error message. ;****************************************************************************************** bank sine_gen_bank mov w,temp mov freq_count_h,w mov freq_acc_h,w ; save the upper byte in the input register mov w,temp2 mov freq_count_l,w ; move it into freq_count_l clc ; Multiply freq_count by 5 because with the known interrupt ; rate, this is the constant to use. rl freq_count_l ; First multiply freq_count by 4 rl freq_count_h jc input_error ; If the input was too high, say "error" rl freq_count_l rl freq_count_h jc input_error ; If the input was too high, say "error" add freq_count_l,w ; freq_count = freq_count + 4(freq_count) add freq_count_h,freq_acc_h ; = 5(freq_count) jc input_error ; If the input was too high, say "error" ;****************************************************************************************** ; There is a slight discrepancy between the actual interrupt rate and the ideal interrupt ; rate, but luckily this is easily remedied by performing this calculation: ; freq_count = freq_count - (freq_count/512) ;****************************************************************************************** mov w,freq_count_h ; Compensate for the interrupt rate discrepancy clc ; by performing this calculation: Frequency = Frequency - (Frequency/512) rr wreg ; Divide frequency by 512 stc sub freq_count_l,w ; subtract (frequency/512) from frequency sc dec freq_count_h mov w,#_press_key ; Send out a carriage return. call @send_string clrb rx_flag ;****************************************************************************************** ; Now get into the loop which detects a frequency for 40ms, and then outputs the results ; of the DFT in a level meter on the screen. ;****************************************************************************************** :loop jb rx_flag,start mov w,#_LEVEL ; Send "LEVEL :" message. call @send_string mov fsr,#freq_det_bank ; clear the bank of sin/cos accumulators call @clear_bank setb freq_det_en ; Enable the frequency detectors mov w,#40 call @delay_n_ms ; Detect for 40ms clrb freq_det_en ; Disable the frequency detectors (Enabling the UARTs) ;********************************************************************** ; Now the sine and cose accumulators have been loaded with values which correspond ; with the magnitude of the signal at the chosen frequency. To get the actual ; magnitude, we need to perform this calculation: ; MAG = (SIN_acc^2 * COS_acc ^2)^(-2) ; Just like (a^2 + b^2 = c^2), where c is the magnitude ;********************************************************************** bank math_bank ; Calculation 1 mov input,sine_acc_h mov input2,sine_acc_h call @SignedMultiply ; SIN_acc^2 mov sine_acc_h,answer_h mov sine_acc_l,answer_l mov input,cose_acc_h ; Calculation 2 mov input2,cose_acc_h call @SignedMultiply ; COS_acc^2 clc mov w,answer_l ; Calculation 3 add w,sine_acc_l mov input,w mov w,answer_h add w,sine_acc_h ; (SIN_acc^2 + COS_acc^2) mov input2,w ; Calculation 4 call @sq_root ; (SIN_acc^2 + COS_acc^2)^(-2) ;********************************************************************** ; Now display the detected magnitude on the screen, as a level meter ; composed of stars. ;********************************************************************** mov answer_l,w clr answer_h break jb answer_l.7,:max rr answer_l ; Maximum value is 63 mov w,answer_l :max_enter and w,#3ドルf ; Ensure that the maximum value is 63. mov temp,w mov loopcount,#64 ; Output 1 space the number of stars. test temp :star_loop jz :space_loop ; Output [temp] stars (maximum of 63) mov w,#'*' call @send_byte dec loopcount dec temp jmp :star_loop :space_loop mov w,#' ' ; Output [loopcount - temp] spaces call @send_byte decsz loopcount jmp :space_loop :done_stars mov w,#'>' ; Output a '>' to show the maximum level. call @send_byte jmp :loop ; Do ALL over again. :max mov w,#$ff ; If the input value was maxed out, jmp :max_enter ; show the absolute maximum on the screen. input_error mov w,#_error ; We get here if the user input a value > 13107Hz call @send_string ; 13107 is 65535/5. :CR_loop call @get_byte ; Wait until user presses CR mov w,byte xor w,#13 jnz :CR_loop jmp start ; and restart the process
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