[Coco] Socat drivewire relay to CoCo1

[Tormod Volden]

On Sun, Mar 1, 2015 at 11:09 AM, jon bird wrote:
> Aaron Wolfe writes
>> The coco 1 is a bit of a special case because it cannot reliably
>> operate at 57,600 bps (slow level shifters or some such hardware
>> deficiency compared to coco 2).  Because of this, it must remain at
>> 38,400bps.  The double speed "turbo" mode using the CD pin is not
>> possible as far as I know.  It is also sensitive to cable length, so
>> make sure the serial cable is as short as possible.  Cabling and speed
>> problems often manifest as checksum errors like you are seeing.
>>
>> To ensure the coco is operating at 38,400bps you need to use the
>> correct ROM or DW binary on the coco, the special version for coco 1
>> should only operate at 38,400.  Of course the serial port on the pc
>> side should also be set to 38,400.  The DW server does this when it's
>> told a coco 1 is connected, but since you're working over IP that will
>> need to be done on the machine running socat.
>>
>> FWIW, I wrote DriveWire using a prolific adapter :)  Many people do
>> have trouble with them, so that may be a factor in your configuration.
>> However the checksum issue makes me suspect its either trying to work
>> at 57,600 or the cable itself is causing trouble.
>
>
> Thanks for the info. I am indeed using the CoCo 1 binary, the serial cable
> is ~30cm long. Given that it seems to work reliably in a "local"
> configuration it sounds unlikely that it is the cable itself causing the
> problem. Given the network traffic looks ok the only difference I can think
> of is the timing differences due to it sending over Ethernet.
>
> As an aside though, I also have a CoCo 2 in the cupboard, it needs a bit of
> work before I can use it but (once I fix it) presumably that will then run
> at 56K, does that also need this "turbo mode" configuration on the serial
> cable?

Yes, the CoCo 2 (and Dragon) will run at 56K in "normal" mode. The
"turbo" mode is for double speed of this again, but it is not fully
supported in software and not considered for general consumption. Only
the "turbo" mode software will make use of the CD pin.

>
> A couple of other observations which I forgot to mention earlier, I couldn't
> actually get DW to work when connected directly to the Prolific adaptor. The
> first time around it generates a "Unsupported com operation whilst opening
> /dev/ttyUSB0", then repeated "Handler #0: Serial device in use" messages.
> Given that I don't intend to run DW in this configuration, it doesn't affect
> me but just thought I'd mention it in case there is a bug here.

I have quite some experience with USB-serial chips from developing the
Dragon DriveWire adapters. I evaluated PL2303 but found them less
reliable when used with DLOAD and DriveWire. I have also read
something about these chips being pirated on large scale and giving
Profilic undeserved bad reputation. I do have some PL2303-based
adapters at work that are running 24/24 for years so they cannot all
be bad. FTDI adapters sometimes have extra functionality but IMO are
overprized for simple USB-serial conversion, and the driver situation
is complex (many versions, trouble on Mac, non-free drivers on Linux,
etc). All my adapters are using Silicon Labs CP210x chips. As far as I
(and meanwhile many users!) can see they work 100% reliably with
DriveWire, and the drivers are straight-forward on all platforms.

+1 on Gene's comment, although my knowledge of this probably
originated from him anyway :) . If you replace the op-amp you might be
able to use the "CoCo 2" software and configuration.

Tormod