> > Joep > > > > vasile surducan wrote: > On 11/14/09, Wayne <[email protected]> wrote: >> >> vasile surducan wrote: >>> If you are using the hardware UART, there are some computations which >> tell's >>> you the error for various crystals. Take a deep look to the Stef's "usart >>> common.jal" from the distribution pack and to the microcontroller >> datasheet >>> USART section, you will find the formula for error detection and spbrg >>> computation. But 9600bps must work with 4MHz crystal or the internal >>> oscillator. The problem is the internal oscillator stability, not the >>> particular value of the oscillator. >> vasile >> >> I am not using the hardware UART. The k107 backpack is a serial >> interface to a LCD. It uses 1 pin to communucate to the LCD and, >> in the version I have, only at 9600 Baud. I am using the >> serial_software lib and with a 20MHz clock it works very well. >> >> My goal was to get an LCD working on 8 pin chips, like the 12f509. I >> 'thought' that I could use the internal 4MHz clock to generate the 9600 >> Baud clock. I must have mis-read or understood incorrectly. > > > > Ok, understand now. You are using the serial software library. You can use > the internal 4MHz clock, but almost sure you have to adjust the OSCCAL > register for a valid communication. I've did it on a few modules (less than > 20) with PIC16F676 at 115200 and gave up when realised that every chip need > modifications of the OSCAL value. Since then I'm using crystals every time I > need communication without headaches. >
Thanks for that! I will now see what I can find on how to do OSCCAL adjusting. I know I've read about but now I have to understand it. This is great! I really appreciate you mentioning that. I'm off to read some more. :-) > As I've seen (never used) the serial_software library is optimised for > 20MHz, however it uses the compiler build in delay, so it must work at 4MHz > too. Best Regards Wayne > > >>> However I've seen at least twice a situation when the usart common.jal >> does >>> not compute correct the spbrg value, without being able to catch the >>> problem. So the question for other guys is how they debug such kind of >>> errors as long there isn't a valid communication for terminal debugging? >>> >>> I didn't figure a usefull way of using "pragma error". Old jal had >> "pragma >>> test assert " which was a damn good feature. How do you use the "pragma >>> error" for debugging? >> I have seen that in some of the libs also but have not found anything >> else about how to use it. I probably missed it or, more likely, didn't >> understand it. :-( > > > Forget it at this moment. > > Thanks for the reply! >> Regards >> Wayne >> >> >> >>> Vasile >>> >>> >>> On 11/13/09, Wayne <[email protected]> wrote: >>>> Hi guys >>>> >>>> Finally made some progress on the k107 backpack. Thanks to a comment >>>> made by Rob, I tried a 20 Mhz resonator on the 16f628a and it finally >>>> displayed the 'correct' characters on the LCD. The same program did NOT >>>> work using 10,8 and 4 MHz resonators or with the 4MHz internal clock. It >>>> seems that the 20Mhz clock gets the 9600 baud rate correct while none of >>>> the others did. Has anyone else had problems getting the 9600 Baud Rate >>>> working? I am using the 'l' version of the compiler (compiled Aug 7 >> 2009). >>>> I had hoped to use the k107 on a 12f509 using the internal clock but >>>> that does not seem to be possible now. >>>> >>>> Wayne >>>> >> > > --~--~---------~--~----~------------~-------~--~----~ > You received this message because you are subscribed to the Google Groups > "jallib" group. > To post to this group, send email to [email protected] > To unsubscribe from this group, send email to > [email protected] > For more options, visit this group at > http://groups.google.com/group/jallib?hl=en > -~----------~----~----~----~------~----~------~--~--- > > --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "jallib" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/jallib?hl=en -~----------~----~----~----~------~----~------~--~---
