[PLUG] com port in guest to usb in host (virtual box)

[Denis Heidtmann]

Measuring with a 'scope with the laptop issuing the  command sigrok-cli
--driver mastech-mas345:conn=/dev/ttyUSB0 --samples 10:

triggering on DTR

DTR goes from -6.6V to +7.6V and remains there 'till 9.64s
RX goes from -2.6V to +6.4V for .48s then again at 2.6s,3.12s, etc 'till
7.32s (10 groups of data pulses after the initial .48s wide group)
RTS sits at -6.4V except for a narrow spike to +6.6V at 2.44s
TX  starts at -6.4V 'till 2.6s, 3.12s, etc where it has a double pulse of
5ms each spaced 1.7ms. These pulse groups start synchronously with the RX
groups.

If I want to get more detail I think I need to trigger on TX.

So it looks like data is being sent. Is it received and sent to a bit
bucket, or not received by the usb-to-serial device?  How to find out?

-Denis


On Thu, Dec 14, 2017 at 10:20 AM, Denis Heidtmann <denis.heidtmann at gmail.com
> wrote:

> The optocouplers in the dmm are reportedly TLV817B.  The emitter resistor
> on the output npn is shown on the schematic to be 1.5K.  I measured it to
> be 7.35K.  The input resistor in series with the LED is listed as 3.3K.  I
> have not opened the dmm to see if the schematic is accurate.  I agree that
> these should not matter. I will get to the sigrok functioning later today
> or tomorrow.
>
> On Thu, Dec 14, 2017 at 10:00 AM, Galen Seitz <galens at seitzassoc.com>
> wrote:
>
>> On 12/13/17 23:03, Russell Senior wrote:
>> > The precise levels are not supposed to make a difference.  Below a
>> > negative threshold and above a positive threshold should be enough.
>> > From memory, original RS232 was +/- 12V, but any remotely modern PC
>> > would use +/- 5V-ish.
>>
>> And the reality is that in most cases a simple unipolar TTL signal will
>> work.  RS232 receivers usually have the logic threshold near +1.4V, plus
>> or minus some hysteresis.  For example, the TI MAX232 has a typical
>> positive-going threshold of +1.7V, and a negative-going threshold of
>> +1.2V.  Another older example is the OnSemi MC1489A quad RS232 receiver.
>>  The typical thresholds for this device are +1.95V and +0.8V.
>>
>> galen
>> --
>> Galen Seitz
>> galens at seitzassoc.com
>> _______________________________________________
>> PLUG mailing list
>> PLUG at pdxlinux.org
>> http://lists.pdxlinux.org/mailman/listinfo/plug
>>
>
>