Posted on 07-04-2008 under avr

As promised, here come the schematics.

Porgrammer Schematics v2 [pdf]

If you want to run this cable with PonyProg, in the Setup->Interface Setup dialog choose Serial. In the drop-down box choose SI Prog API. In the check-boxes below you’ll have to check all except RESET.

Pony Prog Settings

If you’re using avrdude, you’ll have to add the following to your avrdude.conf file.

# SIPROG Inverted programmer
# reset=!txd sck=rts mosi=dtr miso=cts

programmer
  id    = "siprogn"; 
  desc  = "Inverted Lancos SI-Prog “;
  type  = serbb;
  reset = ~3;
  sck   = ~7;
  mosi  = ~4;
  miso  = ~8;
;

More information on the programmer is in the README.

A shot of the cable is below. Its short, but thats because we had already converted the serial port signals to TTL. Of course this is really too short. You can make it a bit longer. Ideally of course, you the longer length should be before the level conversion stage. If you can get your hands on a serial cable, that would allow and instead of plugging the programmer into the computer, you plug it into one end of the cable, you can really extend its operating distance.

Programming Cable

REFERENCES:
LancOS’ site has a few nice serial schematics but all of them use discrete components to do level conversion, and frankly, I dont trust discrete components. At least, not the ones available in our maket. This schematic shows the pin connections on the serial port for the SI Prog programmer. Using this allows us to program using PonyProg.
This page uses a similar Max232 connection. We got the idea to use 10nf capacitors from here, thus reducing the size of the ciruit.

NEXT STEP:

USB. woo!! This is gonna be really easy actually because some circuits are already available online. One of these I really like is ladyada’s circuit. Although I think I can do away with the buffer. And I might have to replace the ATTiny with an ATMega8 because I might not be able to find it in the market.

EDIT [ 14th July, 2008 ] : Corrected a problem with the RESET circuit.