usb problems

[Colin Law]

On 12 October 2014 13:03, Gene Heskett <gheskett at wdtv.com> wrote:
> On Sunday 12 October 2014 07:37:21 Gene Heskett did opine
> And Gene did reply:
>> On Sunday 12 October 2014 02:41:15 Nils Kassube did opine
>>
>> And Gene did reply:
>> > Gene Heskett wrote:
>> > > I am in need of a tool that will effectively do a ping against a
>> > > specified USB port, a port I know there is something on the other
>> > > end of the cable and hub as I just had a printer do a test page
>> > > over the same cabling. Basically I want to send a $55 down the
>> > > cable once a second to a specified port, in thgius case
>> > > /dev/ttyUSB1, for oscilloscope troubleshooting, at least as long
>> > > as trouble doesn't shoot back... ;-)
>> >
>> > If that /dev/ttyUSB1 device is a USB->serial converter, you could
>> > treat it like any terminal device. Therefore, you can use stty to
>> > disable the handshaking lines and set the desired speed (e.g. 100
>> > Baud). Then echo the desired characters to the device:
>> >
>> > stty -F /dev/ttyUSB1 clocal ospeed 100
>>
>> stty -F /dev/ttyUSB1 clocal ospeed 115200
>> stty -F /dev/ttyUSB1 clocal ispeed 115200
>> while true;do echo -n "e" >/dev/ttyUSB1;sleep 1;done
>>
>> > You can cancel the loop with CTRL-C.
>> >
>> >
>> > Nils
>>
>> This works, I can see the once a second red led flicker.  But when
>> measured with the scope, the baud rate seems to be about 55800 (not
>> 57600) unless that "e" is a 2 bits high, 2 bits low etc character.
>>
>> Cheers, Gene Heskett
>
> and after trying to use it at 115200, something is resetting it to 9600?
>
> The .jar that makes a server out of this machine has a config, and that is
> all correct.  Showing:
> Sending command: dw config set DeviceType serial        OK
> Sending command: dw config set SerialDevice /dev/ttyUSB1        OK
> Sending command: dw config set SerialRate 115200        OK
> Sending command: dw config set SerialParity none        OK
> Sending command: dw config set SerialStopbits 1 OK
> Sending command: dw config set SerialDTR false  OK
> Sending command: dw config set SerialRTS false  OK
> Sending command: dw config set SerialFlowControl_RTSCTS_IN false        OK
> Sending command: dw config set SerialFlowControl_RTSCTS_OUT false       OK
> Sending command: dw config set [@name] CoCo 3 on /dev/ttyUSB1   OK
> Sending command: dw config set [@desc] Autocreated 2014-10-12 07:30:40.164
> OK
> Sending command: dw config set UseMIDI true     OK
> Sending command: dw config set CurrentPrinter Text      OK
> Sending command: dw config set Printer(1).OutputDir /CoCo/dwcache       OK
>
> However, any attempt from the CoCo3 to do a directory listing is a read
> error because no data is coming back, the request for that data never
> arrived at this machines USB1 port.
>
> I've taken the serial cable apart, its well soldered on both ends, and
> I've tried the 2nd of 2 identical converters, converters that worked just
> fine in April of this year.  Data is coming out of the CoCo3 with about a
> 10 volt p-p swing centered on ground.  Humm, come to think about that,
> thats low, that circuit is running on the output of an old XT psu, and all
> voltages there are good, +-12 is at least +-11.5 volts.  I've blown
> another S.A.L.T chip would seem to be the correct diagnosis.
>
> This is a jury rigged external power supply as the original was +-8 volts.
> The chip has been replaced once and I have one more spare.  Unfortunately,
> the data available on this chip is limited, and before I blow another,
> I'll order me up a set of 7808 and 7908's to make that +_12 look like what
> its used to.

RS232 specifies a min of +-3 volts up to +-15 if I remember correctly,
so +-5 should be fine.

Colin