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 <[email protected] > 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 <[email protected]> > 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 >> [email protected] >> _______________________________________________ >> PLUG mailing list >> [email protected] >> http://lists.pdxlinux.org/mailman/listinfo/plug >> > > _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
