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Sun Mar 7 15:24:53 CET 2010

Hands-on

Let's forget about the dsPIC assembler until after using the
binutils/gcc toolchain to get something to work.

I'd like to re-focus on actually using Staapl to build things instead
of perpetually redesigning the core.  The problem I got stuck on last
time was building a network of PIC devices.

Let's make this priority one.

Last time the problem was that I don't have an I2C network yet.  This
is the ultimate goal.  In order to get there, I need to build a hub
app.  The hub app takes serial PC communication to anyting else.

The hub needs to run at 40 MHz to be able to get a decent data rate.

It's been a while.  In the summer I got side-tracked by the dataflow
language ideas.  This is where I got last time:

  entry://20090711-151122  better to use a single code image (homogenous network)
  entry://20090627-144638  serial daisy-chaining works
  entry://20090625-131214  standard ``zwizwa connector''
  entry://20090606-125114  ...

The circuit that's on my desk is a 452@40 connected to a 2620@54
(using a 13.5 MHz XTAL).

Daisy chaining worked by connecting the TX of the 452 to the RX of the
2620.  In Staapl this worked like this:

tom@zni:~/staapl/app$ make ttlmono-2620-54.dict
tom@zni:~/staapl/app$ mzscheme ttlmono-2620-54.dict

That didn't work

tom@zni:~/staapl/app$ make 452-40.live

That gave a programming error.  After disconnecting the 2620 it did
program succesfully.  Looping the RX/TX chain on the slave connector
also worked.

scan
Found 1 target(s).
OK

If I recall this has something to do with the reset of the 2nd PIC.
Or the baud rate?

Hmm.. and then out of the blue it works.

scan
Found 2 target(s).
OK

Using `target!' it's possible to switch target.

This does get messed up easily.  I have no idea how to reset it
properly.  This seems to help:

pk2cmd -W1 -R -PPIC18F452


Good.  Cleaned up the target addressing so it is a bit more robust:

  - target-count now sends a nop token to 255 without checking

  - target-receive+id/b checks to see if a message made a round-trip
    without being answered

  - target! performs target-count to make sure the id is valid before
    setting it.



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