How to use a Pololu 5v AVR ISP Programmer to program an AVR at 3.3v

Question

I have a Pololu 5v AVR ISP which I have successfully used to program several Arduinos (a Mega, an Uno and a Pro Mini 5v). I now have a new Arduino compatible clone which is basically a clone of the pro mini 3.3V.

I am wondering if anyone else has used this programmer to program a 3.3V board without issues. I've seen a forum post on pololu's forum which discusses modifications required - but I don't really understand what is necessary.

I've also found the software tool mentioned in the above forum post here and I have downloaded it and built it.

When I run the aforementioned tool I get these options:

PgmCmd: Configuration and status utility for the Pololu USB AVR Programmer.
Version: 1.0.1.0
Options:
 -l, --list list available devices
 -d, --device SERIALNUM (optional) select device with given serial number
 -s, --status display complete device status
 --freq NUM sets the ISP frequency (in units of kHz)
 --linea ID
 or --lineb ID set serial control signal associated with line A or B.
 Valid IDs are: none, cd, dsr, ri, dtr, rts.
 Warning: dtr and rts are outputs: -f option is required
 --swminor HEXNUM AVR ISP software version minor (in hex, e.g. A)
 --swmajor HEXNUM AVR ISP software version major (in hex)
 --hw HEXNUM AVR ISP software hardware version (in hex)
 --vddmin NUM set minimum allowed target vdd (units of mV)
 --vddmaxrange NUM set maximum allowed target vdd range (units of mV)
 --restoredefaults restore factory settings
 --bootloader put device in to bootloader (firmware upgrade) mode

I then ran the --status option with the serial number of my programmer and got this:

Serial number: 00048632
Firmware version: 1.07
Settings:
 ISP Frequency: 200 kHz
 Line A Identity: None
 Line B Identity: None
 AVR ISP hardware version: F
 AVR ISP software version: 2.A
 Target VDD allowed minimum: 4384 mV
 Target VDD allowed max range: 512 mV
Last programming:
 Error: None
 Measured Target VDD Minimum: N/A
 Measured Target VDD Range: N/A
SLO-scope:
 State: Off
 Line A output: Off
 Line B output: Off

From this I deduced that my programmer is currently set at between about 4.38V and 4.89V which I presume corresponds to the 5V approximate voltage of the normal Arduino chips.

Given that the utility program allows me to set both the target minimum V_dd and the target V_dd max range should I therefore set it to something like a minimum of 2704 with a max range of 512 which should put the signal voltages at up to ~3.2V.

Is that all I have to do to get this to work?

• alexan_e: Instead of modifying your programmer to wok with 3v you can also consider buying a USBasp programmer that has a jumper to select between 5v/3v. The cost is less than 3ドル from ebay.
• m3z: I tried the usbasp method. I bought a cheap one off ebay. When it arrived it didn't work until I gave it a firmware upgrade - fortunately I had the other programmer to do that with. Then having had it's firmware upgrade I tested it out on my arduino with mega2560 and my arduino bt with a 328p. I simply tried the blink sketch - on the bt it worked but not on the 2560. Turns out cheap chinese programmers don't always set the fuses correctly and I had to reload the arduino bootloader using my other programmer. I decided not to risk using the usbasp on my 3.3v things.
• Ignacio Vazquez-Abrams: That is actually unfortunate to hear. I have a USBasp clone (Baite EvUSBasp specifically) and have had success with it for the most part, but I've not tried it at 3.3V.
• m3z: fair enough. i guess it's just a pot luck thing on which manufacturers clone you get.

Answer 1

Since AVR ISP is simply a modified form of SPI, the most universal way to handle this is to use a 3/1 level translator such as the MAX3392E. Once you provide it with 5V on V_CC and 3V3 on V_L it will translate the MOSI, SCK, and nRESET signals to 3V3 and the MISO signal to 5V.

• m3z: Thx. I now have 2 more questions - why does MISO stay at 5V? and I'm not sure I can easily get hold of the part you mention but I do have several of these: sparkfun.com/products/retired/8745 Could I use the tx (bi directional despite name) lines of those instead?
• m3z: I should probably add I come from a Software background rather than hardware and have only really used the serial and I2C interfaces of the Arduinos for communication so haven't come across SPI before.
• Ignacio Vazquez-Abrams: "MISO" stands for "Master In, Slave Out". It's the signal going from the slave (the device) to the master (the programmer). That translator should work provided that 1) you have 4 bits total, and 2) you fix the 3V3 side as described in the comments.
• m3z: Thanks for this - eventually though I went with @alexan_e's solution of purchasing a cheap programmer from ebay. I didn't realize they were quite so cheap.
• m3z: I've come back to this solution because cheap ebay programmers are cheap rubbish.