TRW24 Problems...

Wireless & IoT
1

Hi All

I have just found this site and board - joined and think its great. Have to excuse me for a long post but I thought you need to have the full background to the problem.

Wonder if anyone can help me with my TRW24 problem. I just got a batch of 10 of these for a project, as I haven’t used these before I built a copy of the SparkFun evaluation board, programmed an 'LF88 on a breadboard just to test to see if it actually works (all on 3.3 volts).

I use the adapter board to change the pins pitch. On the first unit on inspection before plugging the board in to the breadboard, I noticed after soldering all the pins and the board that I had got a solder blob on the pins. I had to desolder the board and take it off to clear the blob. after resoldering the board and pins back on I marked this unit as possible faulty (maybe due to excessive heat or something - just in case). Built the next unit for two way comms.

Using these two I switched the breadboard on and monitored on my radio scanner for the channel configured, sure enough 2402MHz came alive with data. But the LEDs on the board weren’t indicating two way data, I then used one unit at the time to try to find out which one was not transmitting almost sure that it would be the one with solder blob having died of heat or something. Strangely enough, this unit 1 - the one which originally had the blob removed worked fine but unit 2 didn’t transmit anything. So I made unit 3, plug it in - again nothing. Unit 4 and nothing. Meanwhile unit 1 worked on both PICs (2 development breadboards) but non of the others worked in either.

I started to check unit one for shorts or anything that maybe made it just transmit anything, I am almost sure there was a hairline short between pins DR2 & DOUT2, cleared that it still worked fine. Could not figure out what was going on. I touch solder the pins to make sure there was no bad connection, short etc. it still worked - then used a bit of alcohol to clean the residue between the pins, now unit 1 stopped working, I have now 4 units out of the box that wont come alive for some reason. I would suspect unit 1 to have some kind of problem but that was not the case. I know messing around with unit 1 may not make sense to some but I couldn’t believe that I have assembled 4 units that 3 don’t work and the other 3 all look OK no shorts.

I do a lot of electronics, both logic and RF and SMD, am pretty competent in soldering (beside the original blob!) take protection with static on my soldering etc - in fact have never zapped a chip due to that. So what is going on?!

I know the code is working as I wrote it by converting the demo sample from SparkFun site (in C) to Basic - and as I mentioned it worked fine with unit 1 before it went down. Nothing has been changed on the board. I dont want to assemble any more before finding out what is going on in case something seriously is going wrong somewhere.

When I switch on the board with any of the 4 units on it, I look at the RSSI on my scanner on the channel - on switch on of the board, it shoots up and drops back straight away (only on the channel) - looks like maybe the RF section is ok, but I can not figure out whats gone wrong and would appreciate any help.

Thank you for any help and again sorry for the long post.

Sean

2

My initial suggestion would be to just compile the Sparkfun source code as-is (with a C compiler) and load it into your PICs. Then test them out to see if they will communicate with one another. About 6 months ago I bought 3 of the MiRF-v2 boards and 2 would communicate but another would not. Therefore, if you can prove that the units are in fact defective, Sparkfun will exchange the defective ones at no charge. If all the units do indeed work, then you’re going to have to work on your source code or hardware.

3

Thanks for your reply. I am sure the code is OK, as I have LEDs showing status of them and the loops they are going through also they have been simulated on a couple of simulators including Virtual Breadboard. But I will hook up a scope and see what I can find out. As I said, unit 1 worked fine until I started to check it out. I may also assemble another 2 units just to see if I have got a bad batch of them. But non of this is making any sense to me.

4

Sorry Seanstevens, only thing I can’t understand from your explanation: have you seen real data moving back and forth, or just saw the Spectrum analyzer showing a transmission?

thanks

5

Hi DarioG - I have a top of the range radio scanner, you can program the frequency in and it goes there. When unit one was working, based on the calculation of the frequency, I went to 2402GHz and actually could hear the data packets being transmitted. It was my unit 1 not anything else as I tested it by switching the curcuit on/off. Also the Received Signal Strength Indicator (RSSI) would give me a full deflection. So in short, No spectrum analyzer, but yes I could hear actual data packets (square wave sound) but not visualy checking the data packet. I will try to do that tonight.

Thanks

6

I see.

What I meant , is that you may well be having an address or CRC error…

You transmit, but the wrong bytes!

BTW, I too tried to “hear” the packets with a short-wave radio… but I got much noise from the USB PIC there around!

I resolved in measuring the consumed power, to check if the unit was switchng to TX.

7

I understand now what you mean, but the sample C code from SparkFun written to test out the development boards they sell continuously configures the transmitter then sends a packet, listens for incoming data. If it doesn’t hear any data it repeats the loop again. It was this transmission which I was picking up as square wave clicks and noises, regardless of any CRC or addresses.

Short wave would be just too noisy and way out of the frequency range. I will be checking my circuit with a scope to see if I can find out anything.