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Questions on implementing TDMA

 
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raptorman



Joined: 08 Mar 2008
Posts: 12

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Questions on implementing TDMA
PostPosted: Sat Aug 10, 2013 2:24 pm     Reply with quote

I'm trying to implement some sensors on SBUS2 for my RC hobby. I program for a living but only in iOS and Visual Studio. I dont expect any code, just some suggestions on implementing the design. I'm using a 18lf14k22 and CCS compiler 5.011. I'm also including an image that shows the overall data stream.

I have a 100k Serial Stream with 4 sections of main data consisting of 25 bytes each with a ending byte that identifies which main section of data. In between each main section, you have 8 slots of sensor data consisting of 3 bytes for each slot. I'm creating my own sensors and putting the data into 1 of 32 unused slots. I'm receiving the main and slot data thru the uart.

So the question on design is how to sync up with the main data so I know where I'm at. This is what I was thinking:

Sync up with the data:
Wait for the serial to go high using an interrupt-on change.
Start timer.
wait for it to go low using an interrupt-on change.
if timer less than 5ms(time from last slot to main data), repeat the above.
If timer over 5ms its should be starting the next main section of data.
I have the last main section of data, its ending byte from the uart.
Look at the previous ending byte and I know where I'm at.

Once the program knows where it at, I can calculate when to put data out into the slots. That brings up the next design phase of precise timing the output of the data using the uart or bit-banging.

Anybody else have a better solution?

Thanks,

Jerry

Couldnt get image to display so click URL:
http://rc.runryder.com/helicopter/rr/rrpv.htm?d=/helicopter/gallery/32504/&IN=1&TZ=-7&a=0&s=0
temtronic



Joined: 01 Jul 2010
Posts: 9243
Location: Greensville,Ontario

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PostPosted: Sun Aug 11, 2013 6:21 pm     Reply with quote

I didn't 'google ' too long but...
There seems to be a lot of 'activity' with Ardunios and SBUS2, so you
could port their C code into CCS C code.

You've probably already hit the net..but providing you've got working hardware, the code conversion should be fairly straightforward, and can be easily tested on the bench.

hth
jay
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