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Tranceiver adjustment

Posted: Tue Jul 03, 2012 8:30 am
by achillis1
Hello,

I have been experimenting with tranceivers and more specifically the following:
HM-TR433/TTL from Hope Rf electronics.
2 years ago when I was doing the experiments- communicating between 1 tranceiver with another- I managed to establish a communication for a few days but after something went wrong. 2 years later I do not remember what I did and my proto test board is damaged.
Now I built up 2 new board and try to communicate again but with no luck.


Long story short, the tranceivers communicate with RS232 method of the MCU. I connect the Rx and Tx pin of MCU to the Tx and Rx pin of tranceiver respectively.

1. On the set up utility for the tranceiver are some options that need to be set up. I want to ask if any of them has to do, or to be changed via flowcode in order to match up.
I have selected the same baud rate, 8 bit, no check and 1 bit stop. However there are some other options as well. The "RF parameter" which options span from +-15kHz up to +-240kHz. The "PA level" from 0dBm to -21dBm and "RX bandwidth" from 67-400kHz. Do I have to change these values to specific ones in order for the tranceiver to communicate with the MCU?

2. Also I have noticed that in Flowcode at the RS232 properties, there is a window that says if I use 20Mhz crystal it will have a small percentage of error but if I use the 19.6Mhx crystal then it will have a zero error. So if I use the 20Mhz most likely it will not be able to communicate with tranceiver?

3. Do I have to amplify the signal coming from the Rx and Tx pins of MCU?

4. Some manufacturers say that must a decoder must be interpolated between the MCU and tranceiver, so that the data be sorted in packets. (manchester coding)


Thank you in advance,

Best Regards,

Andreas Achilleos

Re: Tranceiver adjustment

Posted: Tue Jul 03, 2012 2:27 pm
by Benj
Hello Andreas,

Here are some brief answers to your questions, not really an expert on the subject.

1) RF parameter - Sounds like this might be the RF channel, A RF band can be split up into X channels each with 1:X of the band's bandwidth.
PA - Preamp? The amount of amplification done to the signal before it goes into the receiver circuit? A higher gain will detect a weaker signal but may also pick up some noise.
Bandwith - This is essentially how many of the X bands you will be able to detect signals on. You can make this narrow to detect only a specific channel or wide to listen to as many channels possible.

2) The small percentage of error at 20MHz should not be enough to stop the UART from working correctly, especially at lower bauds like 9600 or 19200bps.

3) No amplification is required. Voltage is key, check your target microcontroller and the transceiver are running at the same voltage. A lot of transceivers will require a source voltage of 3V3 so either run your micro at the same voltage or you will need some additional circuitry to do the logic level voltage shifting on the signals. A microcontroller running at 5V can normally detect a 3V3 signal as a logic 1 so you generally only have to level shift your microcontroller outputs eg the TX pin. I think UARTs may be different so be careful here and test before you commit.

4) Cant really help with this i'm afraid, had a quick look and this seems to be a way of combining a synchronous serial clock and data signal into a differential output which could be used for high noise rejection on long lengths of cable etc.

Re: Tranceiver adjustment

Posted: Thu Aug 02, 2012 10:41 am
by achillis1
Hello,

I have finally made it and the tranceivers are now communicating!

So if anyone needs to add some 433Mhz connectivity to their project these tranceivers do the work!

Bets Regards

Andreas Achilleos

Re: Tranceiver adjustment

Posted: Thu Aug 02, 2012 2:27 pm
by DavidA
Thanks for lettings us know :)

Re: Tranceiver adjustment

Posted: Thu Aug 02, 2012 4:57 pm
by dazz
achillis1 wrote:Hello,

I have finally made it and the tranceivers are now communicating!

So if anyone needs to add some 433Mhz connectivity to their project these tranceivers do the work!

Bets Regards

Andreas Achilleos


Hi Andreas

Can you post the steps taken to get it working, as it will help someone else if they get stuck

Regards
Dazz

Re: Tranceiver adjustment

Posted: Fri Aug 03, 2012 8:28 pm
by achillis1
Hello,

Actually I didn't do something to get it working; because it needed something specific but I just eliminated something I was doing wrong and also placed the tranceiver to a better board! :)

I am attaching the datasheet. Actually the connections and procedure is as described in the datasheet, no rocketscience!

Just remember that the MCU that will transmit the data must be connected to the Rx pin of tranceiver( Tx of MCU) and the MCU that will receive the data must be connected to the Tx of tranceiver (Rx of MCU).
The tranceiver that gets data from MCU in order to send them over the air, the red LED blinks and if it receives data over the air the green LED blinks.

Also it is possible if you interpolate to the tranceiver a RS232 to TTL converter and then connect the converter on a PC and use the set up utility (exe)of the the tranceiver then you can connect to the tranceiver and make some changes, including baud rate.
I have used a RS232 to TTL converter from futurlec.com and worked..

Best Regards