Re: [Amforth] grasping at straws with evaluate

[David Wallis]

Hi Matthias,

Thanks for the reply. I've made a small breakthrough, although I don't have
it working yet. Initially the only difference between a setup that worked
and one that didn't was that the scenario that failed ran on battery power
and had an xbee radio plugged in rather than an ftdi USB chip. Debugging
over the USB is a nightmare because you can't get to forth - just send xbee
packets.

However, I can now recreate the problem over USB, and it seems to be a
hardware oddity. If I disconnect the USB power link and run the board off
batteries it fails to update the counter. However, I have to boot the
device off batteries and then plug the usb in for it to stop incrementing.
If I have the USB board plugged in first it increments the counter
properly. I guess the tx and rx lines are giving some power to the device,
which is a bit naughty, but it didn't go bang ;)

So, it appears to only take effect when it boots on battery power. Why this
buggers up evaluate but the rest of forth works ok is very bizarre, but
that seems to be the situation. However, after my turnkey has finished and
I'm dropped back to the prompt, evaluate works!??

I have a couple of questions:

Can I safely use (evaluate) by itself when evaluating RAM strings? It just
makes it less complex and in my final application the string to execute
will come over the xbee and will be in RAM.

Also, can you explain the stack comments that you have put on (evaluate) \
i*x addr len -- j*y

Many thanks for your help.

David
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Re: [Amforth] grasping at straws with evaluate

[Matthias Trute]

Hi David,

> So, it appears to only take effect when it boots on battery power. Why this
> buggers up evaluate but the rest of forth works ok is very bizarre, but
> that seems to be the situation. However, after my turnkey has finished and
> I'm dropped back to the prompt, evaluate works!??

Even more strange. TURNKEY is called in WARM as the last action before
QUIT takes over that starts the REFILL/INTERPRET loop. I see nothing 
that may affect the RAM content at HERE. 

Are you using WORD? It uses the RAM at HERE too, but it is no longer
part of the default word lists, I prefer the newer PARSE-NAME for that.

> 
> I have a couple of questions:
> 
> Can I safely use (evaluate) by itself when evaluating RAM strings? It just
> makes it less complex and in my final application the string to execute
> will come over the xbee and will be in RAM.

Sure.

> 
> Also, can you explain the stack comments that you have put on (evaluate) \
> i*x addr len -- j*y

the string at addr/len is a forth program, it can change the stack
content. Imaginge a "+" at addr/len. That would take 2 cells from the
i*x pool and leaves one cell as the j*y. THe EVALUATE strings are not
like interrupts without stack effect. In general at least.

Matthias

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