Programming custom Arduino Mega with Arduino Uno

Question

I'm making a custom board with AtMega2560-16AU as MCU and CH340G as bootloader (schematic can be seen in the picture). I have printed the custom PCB and soldered everything in place now I want to program the bootloader.

pcb schematic

I connected my Arduino UNO with my custom board like shown in the fritzing schematic below. My custom pcb doesn't look like Arduino MEGA but the connections are the same.

connections

I go to Arduino IDE and upload the ArduinoISP example (baudrate:115200) while choosing programmer as "Arduino as ISP". step 1

And when I upload the example I get a response like this:

avrdude: Version 6.3-20190619
 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
 Copyright (c) 2007-2014 Joerg Wunsch
 System wide configuration file is "C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr/etc/avrdude.conf"
 Using Port : COM4
 Using Programmer : arduino
 Overriding Baud Rate : 115200
 AVR Part : ATmega328P
 Chip Erase delay : 9000 us
 PAGEL : PD7
 BS2 : PC2
 RESET disposition : dedicated
 RETRY pulse : SCK
 serial program mode : yes
 parallel program mode : yes
 Timeout : 200
 StabDelay : 100
 CmdexeDelay : 25
 SyncLoops : 32
 ByteDelay : 0
 PollIndex : 3
 PollValue : 0x53
 Memory Detail :
 Block Poll Page Polled
 Memory Type Mode Delay Size Indx Paged Size Size #Pages MinW MaxW ReadBack
 ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
 eeprom 65 20 4 0 no 1024 4 0 3600 3600 0xff 0xff
 flash 65 6 128 0 yes 32768 128 256 4500 4500 0xff 0xff
 lfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
 hfuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
 efuse 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
 lock 0 0 0 0 no 1 0 0 4500 4500 0x00 0x00
 calibration 0 0 0 0 no 1 0 0 0 0 0x00 0x00
 signature 0 0 0 0 no 3 0 0 0 0 0x00 0x00
 Programmer Type : Arduino
 Description : Arduino
 Hardware Version: 3
 Firmware Version: 4.4
 Vtarget : 0.3 V
 Varef : 0.3 V
 Oscillator : 28.800 kHz
 SCK period : 3.3 us
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.00s
avrdude: Device signature = 0x1e950f (probably m328p)
avrdude: reading input file "C:\Users\ahmet\AppData\Local\Temp\arduino_build_251950/ArduinoISP.ino.hex"
avrdude: writing flash (4354 bytes):
Writing | ################################################## | 100% 0.68s
avrdude: 4354 bytes of flash written
avrdude: verifying flash memory against C:\Users\ahmet\AppData\Local\Temp\arduino_build_251950/ArduinoISP.ino.hex:
avrdude: load data flash data from input file C:\Users\ahmet\AppData\Local\Temp\arduino_build_251950/ArduinoISP.ino.hex:
avrdude: input file C:\Users\ahmet\AppData\Local\Temp\arduino_build_251950/ArduinoISP.ino.hex contains 4354 bytes
avrdude: reading on-chip flash data:
Reading | ################################################## | 100% 0.53s
avrdude: verifying ...
avrdude: 4354 bytes of flash verified
avrdude done. Thank you.

As far as I know so far there's no problem.

And now I move to step 2 which now requires me to switch the board to ArduinoMega from tools. And click burn bootloader. enter image description here

When I click burn bootloader I get a response like this:

avrdude: Version 6.3-20190619
 Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/
 Copyright (c) 2007-2014 Joerg Wunsch
 System wide configuration file is "C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.42.0_x86__mdqgnx93n4wtt\hardware\tools\avr/etc/avrdude.conf"
 Using Port : COM4
 Using Programmer : stk500v1
 Overriding Baud Rate : 19200
 AVR Part : ATmega2560
 Chip Erase delay : 9000 us
 PAGEL : PD7
 BS2 : PA0
 RESET disposition : dedicated
 RETRY pulse : SCK
 serial program mode : yes
 parallel program mode : yes
 Timeout : 200
 StabDelay : 100
 CmdexeDelay : 25
 SyncLoops : 32
 ByteDelay : 0
 PollIndex : 3
 PollValue : 0x53
 Memory Detail :
 Block Poll Page Polled
 Memory Type Mode Delay Size Indx Paged Size Size #Pages MinW MaxW ReadBack
 ----------- ---- ----- ----- ---- ------ ------ ---- ------ ----- ----- ---------
 eeprom 65 10 8 0 no 4096 8 0 9000 9000 0x00 0x00
 flash 65 10 256 0 yes 262144 256 1024 4500 4500 0x00 0x00
 lfuse 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
 hfuse 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
 efuse 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
 lock 0 0 0 0 no 1 0 0 9000 9000 0x00 0x00
 calibration 0 0 0 0 no 1 0 0 0 0 0x00 0x00
 signature 0 0 0 0 no 3 0 0 0 0 0x00 0x00
 Programmer Type : STK500
 Description : Atmel STK500 Version 1.x firmware
 Hardware Version: 2
 Firmware Version: 1.18
 Topcard : Unknown
 Vtarget : 0.0 V
 Varef : 0.0 V
 Oscillator : Off
 SCK period : 0.1 us
avrdude: AVR device initialized and ready to accept instructions
Reading | ################################################## | 100% 0.02s
avrdude: Device signature = 0xffffff (probably .avr8x_mega) (retrying)
Reading | ################################################## | 100% 0.02s
avrdude: Device signature = 0x000000 (retrying)
Error while burning bootloader.
Reading | ################################################## | 100% 0.02s
avrdude: Device signature = 0x000000
avrdude: Yikes! Invalid device signature.
 Double check connections and try again, or use -F to override
 this check.
avrdude done. Thank you.

Now when I clicked burn the bootloader I got a response saying invalid signature. So far I tried to:

1. Change baudrates and try the same steps.
2. Tried to change the avrdude.txt file. I tried to change the signature that was searched for which I couldn't change it because windows 10 wouldn't allow me even though I gave myself all the admin permissions.

So as a solution to this signature problem people have put an electrolytic capacitor that has 10nF or 10uF value between GND and RST pins of the programmer Arduino.

Also when I tried this for the first time I got a value different than "Off" for oscillator in the 2nd step.

So what should I do? Do I need to change my oscillator and try again or do I need that polarized 10uF capacitor?

Sorry for poorly formatting this post. Thank you so much for reading. Any answers would be appreciated.

• chrisl: Please no capslock. Thats like shouting and its difficult to read
• timemage: "10nF or 10uF". 10nF will not to the job. If you've been testing with 10nF switch to 10uF an see what happens.
• Exclose: @timemage I haven't tried either of those. I'm asking if it would help at all.
• timemage: Defeating the UNO's DTR reset mechanism is a necessity when using it as a programmer (arduinoisp.ino). A 10uFcap between RESET and GND is a a way to do that. In short, yes it will help. It should have been mentioned in whatever tutorials and documentation you've been following.
• StarCat: A 10-100uF capacitor on the reset pin of the "master" Arduino prevents it from resetting when the Serial port is opened, which would interfere with the process of writing the bootloader to the Mega2560. There are other ways to prevent this, but this is one of the simplest.

Answer 1

I finally found the problem with this board. I had a 22pF capacitor between RST and GND on the board I had ordered.

You should not have a capacitor there or it should be 100nF, values such as 22pF or 10nF will cause the board to malfunction and therefore you can't burn the bootloader.

• Exclose: I have not yet tried the 100nF cap but I soon will try and update the answer.