[time-nuts] Rapco 1804M - serial problems?
michael.cook at sfr.fr
Sun Oct 16 17:15:31 UTC 2011
Le 16/10/2011 18:34, David J Taylor a écrit :
> I've just got a Rapco 1804M and while it works, within the limits of
> my antenna placement, the RS-232 serial out doesn't read very well,
> and seems to have incorrect characters. The voltage levels look OK,
> and the terminal emulation program is set to 4800 baud, 8-bit, no
> parity, one stop bit, no flow control. I've tried other
> combinations. As near as I can measure, the baud rate is 4800.
> Here's some sample output:
> UTC Time : 16:65:19 16/10?1q
> UTC Time : 16:25:20 16/10/11
> Position : 53 54.406 N 002 12.075 W 0239 M
> PDOP : 02
> Sat PRN : 28,19,32,01,11<22
> Sat levål : 00,12,13,06,05,03
> Fix, Mode : 2D , Coarse
> UTC Time : 16:25:21 16/10/11
> UTC Time : 16:25:22 16/10/11
> UTC Time : 16:25:23 16/10?11
> UTC Time : 16:25:24 16/10/11=
> UTC Ti}e : 16:25:25 16/10?11
> UTC Time : 16:25:26 16/10?11
The data is nearly all good, so probably not a rs232 rate issue. Looking
at the transformations in the above data,
/ => ?
, => <
CR => =
m => }
they are all single/multiple bit flips in the top nibble of the
character hex value. Maybe it's a UART that has hickups.
I couldn't find a schematic, but may be worth looking to see what's
connected to the RS232 tranceiver chip..
> The same serial port works correctly with 9600 baud Garmin signal, and
> I don't have any other available computers with spare RS-232 ports I
> can test against.
> Am I missing the obvious, or is there something wrong with the serial
> port? I do appreciate that the serial port isn't critical to the
> correct operation of the 1804M, but this has cast doubts about this
> particular unit into my mind!
> David GM8ARV
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