[time-nuts] PRS 10 and serial port communication

Hal Murray hmurray at megapathdsl.net
Fri Mar 4 04:43:49 EST 2016


> As I already write PRS10 is configured as serial communication. With
> oscilloscope I can see serial signals, but when enter this signal in
> computer with TTL level USB2serial converter all information is repeatable
> character unknown for me and not as described in manual. 

You may need to add or remove an inverter in there.

Most serial ports on microprocessors and USB to serial chips are expecting a 
TTL to RS232 level shifter and the standard level shifter chips all have an 
inverter.  If there are 0 or 2 inverters it should work.

Some GPS modules don't have any level shifter.  Some devices include an 
inverter but not the level shifter.  That doesn't meet specs but it generally 
works if you connected it to a real serial port (with level shifter).

I would connect a scope to the output side of the USB to serial chip and send 
it occasional characters and use that as a reference for what a character is 
supposed to look like.

Then look to the input side and see if it looks similar.  In particular, 
verify that the idle level is the same.  Then check the baud rate and parity.



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