Serial output problem using 08 NMEA simulator

[yachtbits]

The purpose of this is to simulate NMEA 0183 format heading information that would normally be provided from an electronic compass used on a boat.

What I'm trying to achieve is,
output from the serial out a single, fixed data string. Then after a short delay, loop back to repeat.

The format for the data string needs to be as follows;

$KMHDM,0.0,M*00<CR><LF>

I have it all working okay apart from the <CR><LF> at end of the data string.
These represent <Carriage Return> and <Line Feed>. These are crucial to making it work.

Any ideas how I get the 08 to output <CR><LF> at the end of the string?

All help greatly appreciated.

kev

 

[andrewpro]

the cr and lf I believe are ascii characters 13 and 11 respectively (I could have that backwards, but I dont think so). You could try sending them. How are you reading the serial data? Is it in a terminal program?

 

[yachtbits]

for testing purposes, hyperterminal is being used. I can get it outputting the data, but not CR or LF.

Ulimatelty, the device will be connected to a Radar display to simulate Magnetic North Heading data.

Looked up ASCII codes and 10 & 13 are what I need, how do I put them into the string? current code is,

label_6: pause 500
SERTXD ("$KMHDM,000,M*00&quot
goto label_6

Cheers Kev

 

[Simmicht]

Cr LF is characters 13 and 10 respectively

I was wanting to do nearly the same thing. How is the check digit calculated?

SERTXD ("$KMHDM,000,M*00",13,10)
 

Edited by - simmicht on 4/13/2005 11:35:02 PM

 

[yachtbits]

just programmed using suggestion by simmicht and it looks spot on with hyperterminal. I will test it on the radar system over the weekend and will report back afterwards.

As for check sum calculation, I can't say I know. I connected a NMEA compass to hyperterminal and then swung it to read 0 degrees. checksum at that heading was 00!

But I have found this explination in a GPS manual, I would think it would be the same for all strings, but this did apply to GPS strings. The manual and a similar explination was found on google using NMEA CHECK SUM.

Checksum Field: The absolute value calculated by exclusive-OR the 8 data bits of
each character in the Sentence,between, but excluding “$” and “*”.
The hexadecimal value of the most significant and least significant
4 bits of the result are convertted to two ASCII characters ( 0-9,A-F ) for transmission. The most significant character is transmitted first.