New developments USB – RS485


Well, it’s been a while since the last update so here it goes: we are preparing a few products which will be available in the shop, and as always the people that built them know them better. We’ll have a bit of a description of the manufacturing process going through all the required stages.

What will the products be?

Here it is : USB to RS485 adapter..

And the revised schematics:


USB - RS485 adapter

And the test results are in..

Signal integrity test:

Test conditions:

Cable: 30 meters of twisted pair subsea grade cable 120 ohm terminated

Driver: USB-RS485 Adapter with the 120 ohm terminator jumper ON.

The character ‘U’ (ASCII 0×55) sent via a terminal (PUTTY) with 8 bits data, 1 start bit, 1 stop no parity

The baud rate was set for 115200 bps, 50000bps, and 1Mbps, the waveforms were captured with a 1Gs/s digital storage scope triggered on the start bit.


Character ‘U’ was captured on the scope at the far end of the cable (30m)

The speed is 115200 bps


A detailed view of a bit at 115200 bps





The bit rate was increased to 500.000 bps and the charaRS485_1Mbits_char_signalcter was sampled again.





This detailed bit view shows no sign of reflections on the falling and/or rising edges of the signal.





Finally the  view of  a 1Mbit/s signal over 30m of terminated cable.




The signal integrity is maintained over 30m of twisted pair cable, terminated at both ends, driver and receiver. Signals are sampled on the far end (receiver side) with a digital storage oscilloscope at 1 Gs/s.
This entry was posted in Projects, RS485, Technology, USB and tagged , , . Bookmark the permalink.