SparkFun Forums

[Efren]

Hi, Mr Sparky: if you have done many projects, can you put some in a internet page?
At least the ones don't be against your privacity. particularly the ones with microcontrollers.
We particularly are using RS232 protocol in a PIC16F628A. The oscilloscope shows that the receiver outputs garbage at the begining of every transmission (like some "attack time") so, we send a chain of bytes with a sequence. For rexample, 54 45 several times, then another byte as "begin message" and some checksum at the end and a couple of "end transmission" sequence.
We have heated the PIC puting the solder iron over both, the transmitter and the receiver while it is sending or receiving and it always loses some bytes every second or two, due possibly the acumulative error in timing for the small differences in clocks. It can be known that there are lost data because the PIC raises error flags in its RS232 interface

Greets

P.D. This forum is great. I hope there be more people joining everyday.

[Moore Logic]

Efren,

Check to see if the TX pin is starting out high as this will mess up the first few charaters transmitted due to missing the start bit and using the first data bit as the start bit.

Jamie Moore

[sparky]

What's this about using soldering iron to heat test things!? I love it!

I'm afraid I just don't have the time or the documentation that I'd like to have on any of my RF projects. The best I've found with the KLP links is to use a constant datastream (see Foamware project). If you are trying to pass data back and forth you have to deal quite a bit with rejection and corruption within the first series of bytes.

Sounds like you're on the right track. Use the UART on a PIC and make sure you are at or lower than 4800bps.

-Nathan

[phalanx]

I highly recommend against using the hardware UART with that particular transmitter/receiver pair. It does not have any encoding or protocol standards in its hardware so it is up to you to design them. The UART on the PIC is very powerful, but it was designed with wires in mind where you do not have to deal with the noise and syncronization issues which are inherent in wireless systems. Don't get me wrong, you can hook the UART directly to your transmitter, but the system will perform much more reliably using a software serial port with a custom protocol, encoding scheme, and CRC checking.

There is a thread on this message board where someone was having similar issues as you. There are a number of good recommendations and links that can be found in it.

http://www.sparkfun.com/cgi-bin/phpbb/v ... .php?t=246

If you have any other questions, let us know! Good luck!

-Bill