OK. Seems OK. Well, probably something with the code (since we havn't seen it)... :-) The PIC shouild not stop simply by connecting the GND. Maybe the "RX" is not connected to the correct MAX232 pin ? /Jan-Erik. Adam Walley wrote 2012-01-05 15:35: > Ok, > > Here is a simple drawing, showing the most basic layout I have tried. All > PIC pins set to digital out, comparator off, GPIO1 is TX to PC's RX line > and GPIO2 is an LED which shows me when the program starts and stops and > blinks between cycles. The code should send the letter 'K' five times ove= r > the TX pin before the PIC goes to sleep. > > I am using the MPLAB IDE with some assembly code. I am assuming the codin= g > and subsequent programming of the chip all works, because I have > successfully written to the EEPROM and confirmed its contents. I have als= o > got a working I2C interface with an LM35 temperature sensor (this is part > of my frustration: I can read the temperature and put it in the EEPROM, b= ut > I cannot get the *&^*! RS232 to send it to the PC). > > What am I doing wrong? > > P.S. I can confirm that shorting pins 2 and 3 on the PC side does echo an= y > characters typed, so that all seems fine. > > On 5 January 2012 13:31, Jan-Erik Soderholm= wrote: > >> Hi. >> >> Could you be more specific on what is connected where ? >> Pin numbers and so on. Best is a schematic... >> This *should* work, of course. :-) >> >> Jan-Erik. >> >> >> Adam Walley wrote 2012-01-05 14:10: >>> Hello, >>> >>> I have been struggling to establish communication between my laptop and= a >>> pic12f675. I am needing some help to get this working, because it's >>> starting to drive me nuts. I have tried various methods, but the >>> show-stopper always seems to be when I connect the laptop's serial grou= nd >>> to the PIC's. I'm sure I am making some basic mistakes, but don't have >> much >>> electronics experience. My set-up is as follows: >>> >>> - 5V power supply (4xAA rechargeable cells) with de-coupling capacitor >>> across + and - lines >>> - 12F675 microchip >>> - laptop with usb-serial adapter listening on COM port with Hypertermin= al >>> - some simple PIC code, which blinks an LED on one pin, and transmits a >>> bit-banged letter 'K' at 9600 8N1 on a second pin >>> >>> I would like to get to the stage where I can fine-tune my code, as I >>> suspect it will need some corrections, but I really need to get the >> wiring >>> right first. >>> >>> The laptop's serial pins appear to be operating at -9.6/+9.6V. I can >> create >>> random characters by simply shorting the DTR and RX lines. >>> >>> I also have a ready-made MAX232CPE board, which works very well between= a >>> PC and a Motorola phone. I have tried to use this with the PIC, but com= e >> up >>> against the same problem: as soon as I connect the ground lines the PIC >>> stops working (blinking LED stops). >>> >>> I have read as many tutorials and FAQs as I could find on the web, have >>> tried different approaches with transistors and mosfets, but still cann= ot >>> get this working. >>> >>> One more point: I have attempted the same exercise with my Desktop PC o= n >>> its serial port, but only get the same results (which hopefully rules o= ut >>> the USB adapter as the culprit). >>> >>> Any help would be appreciated. >> -- >> http://www.piclist.com PIC/SX FAQ& list archive >> View/change your membership options at >> http://mailman.mit.edu/mailman/listinfo/piclist >> >> >> --=20 http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .