[GPS_Standard] Command strings

[Bert, VE2ZAZ]

Hi Rex,

The vast majority of inquiries (and problems) involve the serial link. There are a few possibilities of faults that would cause such behavior. 

Starting with the DC supply, how solid and clean is your +5V on-board supply? What voltage do you feed the controller board with? 

Your problem may also be on the RS-232 serial link itself. Do you have access to an oscilloscope? You should check the swing on the
 RS-232 link. You should actually trace the whole Tx-Rx chain starting 
from the PC to the controller board, and back to the PC. Make sure to check that the charge pump capacitors used on any MAX232 converted chip have their polarity right vs. the MAX232 pinout. Make sure you measure around + 9V and -9V on these capacitors. If you are using a Serial-USB dongle, this may be the cause of your problems. I have seen erratic behavior of these before. You should try an alternate connection method, such as a desktop PC. 

Good luck,

Bert, VE2ZAZ

> From: r.pearson at internode.on.net
> To: gps_standard at mailman.qth.net
> Date: Thu, 26 Jul 2012 16:04:32 +1000
> Subject: [GPS_Standard] Command strings
> 
> Have got the unit working and can send the "P" command to get to get the
> status string but it seems to respond very intermittently.  I get the data
> from the PIC regularly at about a 20 sec interval.
> 
>  
> 
> I have not been able to get the "Txxx" command to do anything.  Have been
> sending T0100 to try to force the DAC to a value.
> 
>  
> 
> I can see the receive data pin on the 18F2220 changing ok.
> 
>  
> 
> Has anybody experienced this problem and would appreciate any suggestions
> 
>  
> 
> Thanks
> 
>  
> 
> Rex
> 
>  
> 
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