IEC project

From: Jim Brain (
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 Brain, Brain Innovations                      
Dabbling in WWW, Embedded Systems, Old CBM computers, and Good Times!

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