Pic18F4550 + SIMCOM SIM900D GSM/GPRS

[ScaleRobotics]

I still think you may need to use a max232 between the PIC and the device as you have mentioned the device works when connected directly to a PC.

if that is the case,

You can invert the comms for the pic18f4550. This will make it possible to talk to a modem without a rs232 chip: http://www.picbasic.co.uk/forum/showthread.php?t=10361

[tacbanon]

if that is the case,

You can invert the comms for the pic18f4550. This will make it possible to talk to a modem without a rs232 chip: http://www.picbasic.co.uk/forum/showthread.php?t=10361

I found it on page 240(datasheet) BAUDCON: BAUD Rate Control Register
Bit 4
1 = TX data is inverted
Bit 5
1 = RX data is inverted
Please correct me if I'm doing it wrong...
Baudcon.4 = 1
Baudcon.5 = 1

regards,
tacbanon

[ScaleRobotics]

That is correct. And make sure your voltages match, so no one gets hurt.

[tacbanon]

And make sure your voltages match, so no one gets hurt.

Sorry to ask this...but to make sure. GSM module I/O Interface UART 3.3V Logic 5V Tolerant, connecting to my LABX2 I think is safe even with the modification of BAUDCON...am right?

thanks for the help,
tacbanon