Folks,
Would appreciate some advice from those here with more Piccolo experience than me. I have an old 128x480 LCD display that I want to use in a project (for a machine tool CNC conversion; hence the need for this ruggedized display, which contains a Hitachi LM215X module). Controller chips for this module seem to be long obsolete. For this and other reasons, I intend to use a Piccolo F28027 to drive it.
The fundamental problem is painting a horizontal line of 240 single-bit pixels, in parallel across 4 quadrants of the LCD at a fixed clock rate of about 1 microsec/cycle. I can slice and dice the bits from my frame buffer/character generator to assemble this 240 x 4 bit stream in RAM, but what's the best way to feed these 240 4-bit nibbles out synchronously at 1 µs each?
1. I can run a clock at 1 MHz and use an ISR to read the next nibble and put it out to GPIO0-3. From testing, I can reliably get into the ISR and the first C instruction in about 24-25 cycles. Might be doable, since I have almost 60 cycles per nibble.
2. I looked at using the SPI peripheral, but it's only 1-bit at a time, not 4.
3. However, maybe I should still use SPI to put out 4*240 = 960 bits at 4 MHz and use an outboard shift register to convert back to 4-bit parallel.
4. Rather than using an ISR, I could monitor a 1 MHz internal clock in a polling loop, and service the RAM-read/GPIO-output that way.
5. Is there a simple outboard hardware solution, e.g., a 240(or more) x 4 FIFO? What chip(s)?
Thanks in advance for any advice. I'll make one of these ways work, but thought it would be useful to ask for some advice before charging off into blind alleys :-)
Mike
