Hello, all!
I’m interested in learning how to communicate between my PC and AVR via the MAX232 and have had a good bit of success in almost all areas except for the consistency of the system. I’m simply looping the MAX232 back to the PC at this point (no AVR in the circuit yet) and am getting a perfect echo of the characters/strings I send but after about 15-20 seconds of operation the terminal just displays random (seemingly) characters and refuses to respond. I’ve tried a few different capacitors and other settings in the terminal but can’t seem to get it nailed down. If anyone has had similar issues and wouldn’t mind sharing their solution I’d greatly appreciate it! The parts/schematics I’m referencing are listed below.
MAX232:
http://www.sparkfun.com/commerce/produc … cts_id=316
Schematic (without the AVR, of course):
http://www.coolcircuit.com/circuit/rs23 … max232.gif
Thanks so much!
There are more signals to RS-232-C then TX and RX. Look up CTS, RTS, DCD, RI and several others. These pins if left open will float and may inhibit communications.
atmega-ist:
Hello, all!
I’m interested in learning how to communicate between my PC and AVR via the MAX232 and have had a good bit of success in almost all areas except for the consistency of the system. I’m simply looping the MAX232 back to the PC at this point (no AVR in the circuit yet) and am getting a perfect echo of the characters/strings I send but after about 15-20 seconds of operation the terminal just displays random (seemingly) characters and refuses to respond. I’ve tried a few different capacitors and other settings in the terminal but can’t seem to get it nailed down. If anyone has had similar issues and wouldn’t mind sharing their solution I’d greatly appreciate it! The parts/schematics I’m referencing are listed below.
MAX232:
http://www.sparkfun.com/commerce/produc … cts_id=316
Schematic (without the AVR, of course):
http://www.coolcircuit.com/circuit/rs23 … max232.gif
Thanks so much!
Loop back serial out to serial in, for the PC’s output stream of characters. No microprocessor involved.
I’ll guess this is the terminal program, not hardware.
The only hardware impact may be RS232 voltage levels that are marginal. Use a 'scope. Confirm you see swings from -5 or more to +6 or more. If not, maybe the capacitors for the MAX232 aren’t the correct value, polarity, etc. An ensure there’s a common ground.
And don’t try more than 56Kbps.
