Programming Prop over RS232

Helen C

I have followed these two threads in order to implement programming of the Prop via a MAX3232 chip.

http://forums.parallax.com/showthread.php/84909-Serial-link-via-MAX3232-IC

http://forums.parallax.com/showthread.php/84805-Propeller-Serial-Programming-Adapter-Testing/page2?p=581926#post581926

My problem seems to be that the implementation of the DTR line from the output of the MAX3232 via the NPN transistor is not working correctly. So I the ability to reprogram only works intermittently if at all.

If I use the Parallax Serial Terminal and tick the DTR box then the prop resets on release of the DTR line but the unit then sends strange characters to the terminal before the system boots properly. If I do the same with the FTDI USB prop plug then there are no strange chars.

Am I doing something wrong?

Cheers

Helen

Tubular

Helen,

Do you have the "BOEn" pin tied to ground, which is the normal configuration? This action changes how the reset pin is configured, from memory.

I'd suggest looking at PhiPi's Propstick design, that had the MAX3232 and reset transistor. I've put Propsticks all over the place using RS232 and they've always worked well.

It'll be something simple.

Tubular

Here's the PropStick documentation
http://elmicro.com/files/parallax/propstickkit-v12.pdf

LoopyByteloose

Using a MAX3232 chip should work, but adds a bit of extra cost and can add some confusion about the DTR line. Since the MAX3232 chip inverts the logic, the addition of the transistor inverts the logic a 2nd time to get it right.

I have used the transistor schematic with great success.. even adapted the whole to be a reciever for RS485 over 100' of wire. There are several adaptations of the how to wire that RTN. Phil's may serve you better.

Helen C

Thanks for the replies. I looked at the propstick info and it looks like exactly what I have implemented and frustratingly it seems to be working again now!

Cheers

Helen