Post by thread:[PIC]: Serial Communication

I'm a newbie using a PIC16F877 trying to develop serial communications between the PIC and in this case, my PC. I followed the instructions in section 10 in the manual and I am pretty sure I have initialized the port properly as I do receive some of the data sent. The problem is that I only get a couple of the characters sent and lose most of the message. This is what I have done below: any suggestions? ;--------------------- ; Main Program Loop ;--------------------- main call init_ports ; set up ports call init_serial ; set up serial comm call displaymsg ; display test message done goto done end ;-------------------- ; Initialize Ports ;-------------------- init_ports clrf STATUS clrf PORTC bsf STATUS,RP0 ; select bank 1 bsf TRISC,7 ; set PORTC 7:6 for async mode bsf TRISC,6 bcf STATUS,RP0 ; select bank 0 return ;------------------------------------- ; Initialize Serial Port ;------------------------------------- init_serial banksel SPBRG movlw D'129' ; set baud rate for 9600 Fosc 20 MHz movwf SPBRG banksel TXSTA bcf TXSTA,SYNC ; set for asynchronous mode bsf TXSTA,TXEN ; enable serial transmission bsf TXSTA,BRGH ; set for high speed (async mode) banksel RCSTA bsf RCSTA,SPEN ; serial port enabled return ;------------------- ; Display Message ;------------------- displaymsg clrf FSR loop movf FSR,w incf FSR,f call showmsg iorlw 0 ; check if end of message btfsc STATUS,Z return movwf TXREG ; send data to register goto loop ;---------------------------- ; Messages to be displayed ;---------------------------- showmsg addwf PCL,f nop dt "TEST MESSAGE",0 -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

> > I'm a newbie using a PIC16F877 trying to develop serial > communications between the PIC and in this case, my PC. The definitive reference for the PIC UART is Fr. Tom McGahee's PICUART.ZIP which is an annotated source for controlling the PIC UART. It can be found at http://mcgahee.freeservers.com/ under the link PICUART.ZIP. Hope this helps, BAJ -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

Davor Tolja wrote: > > I'm a newbie using a PIC16F877 trying to develop serial > communications between the PIC and in this case, my PC. > I followed the instructions in section 10 in the manual and I > am pretty sure I have initialized the port properly as I do > receive some of the data sent. The problem is that I only > get a couple of the characters sent and lose most of the > message. This is what I have done below: any suggestions? Most likely, the data is being sent to the TXREG before it has a chance to send it out. It takes a certain amount of time to shift the data out, depending on the baud rate. This is a non interrupt method of waiting for all TX to finish. ;------------------- ; Display Message ;------------------- displaymsg clrf FSR loop movf FSR,w incf FSR,f call showmsg iorlw 0 ; check if end of message btfsc STATUS,Z return movwf TXREG ; send data to register call TransWt ; <<<<<<<<<<<<<<<<<<<<<< goto loop ; ; ------------------------------------ ; WAIT UNTIL RS232 IS FINISHED SENDING ; ------------------------------------ ; TransWt bsf STATUS,RP0 WtHere btfss TXSTA,TRMT ; (1) transmission is complete if hi goto WtHere ; clrf STATUS ; RAM Page 0 return -- Best regards Tony ICmicro's http://www.picnpoke.com spam_OUTsalesTakeThisOuTpicnpoke.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

Thank you for your suggestions. The reference Byron directed me to will prove to be very useful and I noticed Tony's contributions in that savme document as well. So if that won't be able to help me, then nothing will. Thanks again guys. davor {Quote hidden}> Davor Tolja wrote: > > > > I'm a newbie using a PIC16F877 trying to develop serial > > communications between the PIC and in this case, my PC. > > I followed the instructions in section 10 in the manual and I > > am pretty sure I have initialized the port properly as I do > > receive some of the data sent. The problem is that I only > > get a couple of the characters sent and lose most of the > > message. This is what I have done below: any suggestions? > > > Most likely, the data is being sent to the TXREG before it has a chance > to send it out. It takes a certain amount of time to shift the data out, > depending on the baud rate. > > This is a non interrupt method of waiting for all TX to finish. > > ;------------------- > ; Display Message > ;------------------- > displaymsg > > clrf FSR > loop > movf FSR,w > incf FSR,f > call showmsg > iorlw 0 ; check if end of message > btfsc STATUS,Z > return > movwf TXREG ; send data to register > call TransWt ; <<<<<<<<<<<<<<<<<<<<<< > goto loop > > ; > ; ------------------------------------ > ; WAIT UNTIL RS232 IS FINISHED SENDING > ; ------------------------------------ > ; > TransWt bsf STATUS,RP0 > WtHere btfss TXSTA,TRMT ; (1) transmission is complete if hi {Quote hidden}> goto WtHere > ; > clrf STATUS ; RAM Page 0 > return > > > -- > Best regards > > Tony > > ICmicro's > http://www.picnpoke.com > .....salesKILLspam@spam@picnpoke.com > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's > > -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

Davor Tolja wrote: > > Thank you for your suggestions. The reference Byron directed me > to will prove to be very useful and I noticed Tony's contributions > in that savme document as well. So if that won't be able to help me, > then nothing will. Thanks again guys. > > davor One other thing, try running your PC side software in dos after re-booting in dos mode. Windows takes huge chunks of timeslice and isn't real polite about the ways it does it. -Roman -- http://www.piclist.com hint: PICList Posts must start with ONE topic: "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's

Roman Black wrote: > > One other thing, try running your PC side software in dos after > re-booting > in dos mode. Windows takes huge chunks of timeslice and isn't real > polite > about the ways it does it. > -Roman > > -- > http://www.piclist.com hint: PICList Posts must start with ONE topic: > "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's The best way around Windows is to send data in 8 or 16 byte 'chunks' and then ACK the transfer. I've never(??) had any problems thus far. -- Best regards Tony ICmicro's http://www.picnpoke.com salesKILLspampicnpoke.com -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Roman Black wrote: >Davor Tolja wrote: >> >> Thank you for your suggestions. The reference Byron directed me >> to will prove to be very useful and I noticed Tony's contributions >> in that savme document as well. So if that won't be able to help me, >> then nothing will. Thanks again guys. >> >> davor > >One other thing, try running your PC side software in dos after >re-booting >in dos mode. Windows takes huge chunks of timeslice and isn't real >polite >about the ways it does it. > >Roman > Yes, I have a DOS program that does RS-232 comm, and can run successfully under Windows9x. Since the transferred data is displayed graphically, you can easily estimate the amount of time and frequency that Windows commandeers the cpu [for backgnd/maintenance processing] by looking at data dropouts - it's a "lot". To avoid data dropout, you have to disable interrupts on the PC. [the clock gets a little off kilter, but what the heck]. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Tony Nixon wrote: > > Roman Black wrote: > > > > One other thing, try running your PC side software in dos after > > re-booting > > in dos mode. Windows takes huge chunks of timeslice and isn't real > > polite > > about the ways it does it. > > -Roman > > > > -- > > http://www.piclist.com hint: PICList Posts must start with ONE topic: > > "[PIC]:" PIC only "[EE]:" engineering "[OT]:" off topic "[AD]:" ad's > > The best way around Windows is to send data in 8 or 16 byte 'chunks' and > then ACK the transfer. I've never(??) had any problems thus far. > The best way around windows is to delete it and run your app under dos. I write a lot of CNC and industrial control stuff using turbo C for dos and dos 6. Amazing just how fast your PC can do stuff if it doesn't have crappy operating system built by committees paid per code size and spending all their time blaming problems on the "other" group instead of making it PERFORM. I have written huge apps that load themselves and Mb of data, config etc in 0.1 seconds. So why does my word processor take 7.8 seconds to start up before I can even start typing a simple letter? It's a joke! Sooner Microsoft goes under and becomes history the better. I have windows word processors, graphics editors etc that are slower than the versions from 7 years ago. And my computer/drives are 4 times faster. Doesn't this annoy anyone else? -Roman -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

Roman Black wrote: ....... Sooner Microsoft goes under and >becomes history the better. I have windows word processors, graphics >editors etc that are slower than the versions from 7 years ago. And my >computer/drives are 4 times faster. Doesn't this annoy anyone else? Ahhh, another potential convert for Linux. [you will be contacted by the "Committee" anyday now - hush, hush]. -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics