Charles Craft wrote 2012-01-05 17:02: > What happens if you only connect the grounds - no TX -> RX connection? > I think your going to need something (resistor?) between the PIC and a > RS-232 pin. No, one need a proper RS232/TTL-CMOS converter, such as MAX232. And since he has one (right?), this is a non-issue. > > On 1/5/2012 9:35 AM, Adam Walley wrote: >> Ok, >> >> Here is a simple drawing, showing the most basic layout I have tried. Al= l >> 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 ov= er >> the TX pin before the PIC goes to sleep. >> >> I am using the MPLAB IDE with some assembly code. I am assuming the codi= ng >> and subsequent programming of the chip all works, because I have >> successfully written to the EEPROM and confirmed its contents. I have al= so >> got a working I2C interface with an LM35 temperature sensor (this is par= t >> of my frustration: I can read the temperature and put it in the EEPROM, = but >> 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 a= ny >> characters typed, so that all seems fine. >> >> On 5 January 2012 13:31, Jan-Erik Soderholmwrote: >> >> >>> 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 an= d 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 gro= und >>>> 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 Hypertermi= nal >>>> - 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 betwee= n a >>>> PC and a Motorola phone. I have tried to use this with the PIC, but co= me >>>> >>> up >>> >>>> against the same problem: as soon as I connect the ground lines the PI= C >>>> stops working (blinking LED stops). >>>> >>>> I have read as many tutorials and FAQs as I could find on the web, hav= e >>>> tried different approaches with transistors and mosfets, but still can= not >>>> get this working. >>>> >>>> One more point: I have attempted the same exercise with my Desktop PC = on >>>> its serial port, but only get the same results (which hopefully rules = out >>>> 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 .