RCM2020 not detected with home-made programmer cable


I’m trying to program a used RCM2020 board using a cable I built based on the specs in the PDF:

but it doesn’t seem to work. Says it doesn’t detect the rabbit.

So here’s my question: Does the RCM2020 need a bootloader put into it first? or should my cable work?
Is it possible that the previous user of the RCM2020 board erased the bootloader and thereby caused me to be unable to program it with the serial adapter?

This is the only cable I have, but I have lots of the RCM2020 boards to try, all alike, all from the same source.

If my cable should work, then I’ll keep troubleshooting with scope and logical analyzer. I just wanted to make sure I’m headed in the right direction.

Thanks very much,


If you have built your cable correctly, then it should work. The mode pins of the programming cable allow downloading of bootloader code through the cable so there is no situation where a working core module would not respond over a properly built programming cable. A couple of possible issues:

Make sure you download the proper version of Dynamic C, DC10 won’t work with an RCM2020, you must use DC9.

RCM2020 uses +5V so unlike newer programming cables, the RS232 transceiver chip (3232A) must be a +5V version, not 3.3V.

Good luck

I have DC9.62. Is that close enough to DC9 to work?

My max232 chip is 5 volt capable. I did verify that the reset line is changing states when the DC is trying to detect it.

I’ll get a scope on it and do more checking out and report back.

Thanks very much!


You can also try the serialIO program to check the reset lines and low speed uploads. You can manually set/reset the reset line from there also.

When I stated DC9 I meant any 9.xx version, so DC9.62 is fine. Just wanted to make sure you weren’t trying to get DC10.xx to talk to Rabbit 3000.