From: Jim Brain (brain_at_jbrain.com)
Date: 2004-05-20 03:51:56
Last night, I was able to sniff the IEC port via my AVR controller. The code still needs more work, but I was happy that my experiment worked. Code is running at 14.7456MHz Interrupts are left on during protocol IEC protocol portions (ATN detection, transfer preamble, data transfer) are done via interrupts (EOI handshake is not interrupt driven yet...) Of interest is the bit-banging part of the protocol. Instead of detecting the CLK LO->HI transitions and reading each bit in, I used the built in shift register on the AVR to clock in the byte. Not only does that reduce the IRQ load, but it looks like with a bit of glue, I can send the SRQ line into the shifter to handle burst transfers.... I'm not sure I can use the shift register to send out bytes, but as Marko noted, sending data is much easier than receiving. Code is in C and compiles with AVR GCC. I also noted someone ported uIP to the AVR. My project needs a IP stack, so I'm going to look at that. <>Jim -- Jim Brain, Brain Innovations firstname.lastname@example.org http://www.jbrain.com Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times! Message was sent through the cbm-hackers mailing list
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