Re: Help with Commodore 128D User Port

Hi Leif,

I don't think I have ever used my EZ232 with my C128DCR in UP9600 mode. I
could test and see if I get similar results.

Jim
On Jan 11, 2016 10:41 AM, "Leif Bloomquist" <leif@schemafactor.com> wrote:

> Hi all,
>
> I got my "Wifi Modem" device working with the SX-64, thanks for the
> help!  (The trick was to lower my current limiting to 100 ohms).
>
> I've found a new issue, unique to the 128D and related to the UP9600 hack.
>
> The symptom is that with my device plugged in, the 128D's built-in
> 1571 immediately goes to an error state (activity LED flashing
> constantly) and I can't even read the error channel (PRINT DS$ returns
> blank).
>
> This does *not* happen with a flat 128 and external 1571, so it's
> something related to the 128D - I'm aware the 128D's 1571 has a newer
> ROM revsion (3.1 vs. 3.0) and there is probably an electrical reason
> here.
>
> Here's the schematic for my device:  http://i.imgur.com/OVkLEMG.png
>
> I've found that if I disconnect Pin 5 ("Serial Port 1, from CIA #1")
> it works. With the UP9600 baud hack, Pin 5 is looped back to Pin M
> (TxD).
>
> This is the root of the issue but I'm not sure why.  With other RS232
> adaptors (like Jim's EZ232) that support the UP9600 hack, looping back
> Pin 5 to Pin M (via jumper) does not cause the issue. Also, as
> mentioned this doesn't occur in a flat 128 and external 1571.   So I'd
> like to understand what the issue is before blindly adding a jumper.
>
> More details on my modem:
> https://jammingsignal.wordpress.com/commodore-wi-fi-modem/
>
> Thanks for any help!
>
> -Leif
>
>
> --
> Leif Bloomquist | leif@schemafactor.com | +1 416-737-2328 | Check out
> my blog! http://www.jammingsignal.com
>
> "Every choice, no matter how small, begins a new story." - xkcd
>
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