Reply by Michael Anton August 31, 20082008-08-31
> -----Original Message-----
> From: l...
> [mailto:l...]On Behalf
> Of thirdshoedrops
> Sent: Saturday, August 30, 2008 7:39 PM
> To: l...
> Subject: [lpc2000] LPC2101 ISP w/ 4MHz Crystal?
> I just built my first SMD board, a > href="https://voxan.mersenne.com/gallery/main.php?g2_itemIdR
> 06">controller
> for a nixie-tube wristwatch. I've had various problems with it,
> but have hacked around them to the point that I can (sort of) talk to
> the CPU from a serial port. My intention was to use lpc2k_pgm to
> download code, the same as I do on my 2148 devkit boards. But...
>
> I used a 4MHz crystal for this board. When I power it up with P0.14
> high, it goes into some default (?) code (?) that toggles P0.0 at
> about 41.6kHz (24uS), and puts short, negative-going pulses on P0.1 at
> about the same rate (but they're not synchronized, as far as I can
> tell with my old analog scope).
>
> When I reset with P0.14 held low, it looks like the chip enters the
> ISP: I can sort of talk to it with a terminal program. It sends a
> couple of characters after reset, and sort of echoes what I type (some
> characters are echoed correctly, some incorrectly, and some not at
> all). I send '?', but never get the "Synchronized" message.
>
> The manual says autobaud only works with a crystal >= 10MHz. My next
> step is to find one and solder it in, but is there a baud rate I could
> try that might work with my current 4MHz crystal? Does this sound
> like a somewhat alive system, or should I be planning to
> respin the board?
>
> Thanks!
>

The fastest I can get autobaud to work at with a 12MHz crystal, is
38400, so try a standard baud rata at about one third of that. Perhaps
9600 would work.

Mike

An Engineer's Guide to the LPC2100 Series

Reply by thirdshoedrops August 30, 20082008-08-30
I just built my first SMD board, a href="https://voxan.mersenne.com/gallery/main.php?g2_itemIdR06">controller
for a nixie-tube wristwatch. I've had various problems with it,
but have hacked around them to the point that I can (sort of) talk to
the CPU from a serial port. My intention was to use lpc2k_pgm to
download code, the same as I do on my 2148 devkit boards. But...

I used a 4MHz crystal for this board. When I power it up with P0.14
high, it goes into some default (?) code (?) that toggles P0.0 at
about 41.6kHz (24uS), and puts short, negative-going pulses on P0.1 at
about the same rate (but they're not synchronized, as far as I can
tell with my old analog scope).

When I reset with P0.14 held low, it looks like the chip enters the
ISP: I can sort of talk to it with a terminal program. It sends a
couple of characters after reset, and sort of echoes what I type (some
characters are echoed correctly, some incorrectly, and some not at
all). I send '?', but never get the "Synchronized" message.

The manual says autobaud only works with a crystal >= 10MHz. My next
step is to find one and solder it in, but is there a baud rate I could
try that might work with my current 4MHz crystal? Does this sound
like a somewhat alive system, or should I be planning to respin the board?

Thanks!