On Mon, 18 May 2015 19:39:00 +1000, you wrote: >On 18/05/2015 5:23 PM, Mike Harrison wrote: >> On Mon, 18 May 2015 08:56:05 +1000, you wrote: >> >>> These 16x32 P10 RGB LED panels >>> >>> seem to be cheap and readily available. I've seen DIY projects using >>> them that employ a Teensy3 or similar to drive them. >>> >>> What I'd like to do is use about 8 panels (side by side so 16 x 256 >>> pixels) in a message display. No fancy graphics are required, just >>> static or scrolling text. >>> >>> The text input / commands would be via an RS485 port. My main concern >>> is refreshing the display reliably while processing comms. >>> >>> Is this doable with a PIC or ATXMEGA chip? I have been using the unpai= d >>> version of the XC8 compiler for PIC and Atmel Studio for ATXMEGA projec= ts. >>> David... >> Proably a bit of a struggle on an 8-bit part, but I;m sur it's doable - = much easier on a faster >> device like PIC24 or 32 though >> If only due to RAM available. Obviously you can do without a RAM buffer = by sending data direct from >> a character lookup table, but having a RAM buffer makes life a lot easie= r. >> An issue is you need to generate six SPI serial streams - with a fast d= evice that has pin mapping, >> you can use the SPI hardware and send data sequentially using 2 SPI port= s, mapping them to each of 3 >> sets of pins in turn to do each colour. > >Hi Mike, >I'm happy to learn PIC32 for this. Great idea on the on-the-fly pin=20 >mapping. > >In your opinion is it worth getting the optimised compiler? >David... Probably not - the difference between free and paid versions of the PIC24 = and 32 compilers are MUCH less than the 8-bit. SPI throughput can often be increased significantly by running in 32 bit mo= de, and remember there's a FIFO. ...and if you really need max IO speed, you always have the option of DMA, w= hich avoids any code-efficiency issues! I've done a 32x96 monochrome display using the cheap white chinese signage = panels with 10-bit greyscaling on a PIC32. ...actually thinking about it you can't do the SPI sequentially as you have = a common clock.=20 An option may be to use the parallel master port to output 6 bits at a time= , using the WR line as a clock. Maybe with DMA for max speed, though unless you're doing greyscal= ing, speed shouldn't be a big issue.=20 =20 --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .