315MHz RF, atmega32, RX does not go low.

Wireless & IoT
1

Hello everyone,

I am cross posting this question from AVR Freaks:

http://www.avrfreaks.net/index.php?name … ic&t=96303

I am currently attempting to transmit data between to atmega32s via 315MHz from the following modules form sparkfun:

RF Link Transmitter - 315MHz

sku: WRL-08945

http://www.sparkfun.com/commerce/produc … ts_id=8945

RF Link 4800bps Receiver - 315MHz

sku: WRL-08947

http://www.sparkfun.com/commerce/produc … ts_id=8947

I have followed the tutorial referenced from sparkfun: http://winavr.scienceprog.com/example-a … llers.html

I have verified that I have communication by touching the TX and RX pins, ie, the code seems to be running fine. However, the same cannot be said over the wireless link. To help debug the problem I have attached the TX and RX to a scope. Referring to High.jpg one can see RX as the top trace and TX as the bottom trace. Notice that RX is between ~4.75V and 5V, the shape of the trace suggests that transmission is present. It appears to me that if RX went low then I would be all set. The second plot, Low.jpg is just that, I have connected the RX and TX and I have communication.

I have done an extensive search on this subject but all the discussions I have came across are a little bit to vague. I am not sure if I need to send more “startup bits” or move to Manchester encoding or maybe something completely different. A couple of hints should get me started.

Thank you for your time,

-P

2

Take a look at [this thread. The RX module used for the post you reference ([Running TX433 and RX433 RF modules with AVR microcontrollers) is similar to the [WRL-08948, not the [WRL-08947. Even though the [WRL-08948 RX module has slightly lower performance than the [WRL-08947, it is more forgiving and will probably work for you. Looking at the posts and comments on the [WRL-08947, my guess would be that the TX module was not re-aligned by the manufacturer after the newer RX module was introduced. My recommendation would be to try [WRL-08948 RX module.](RF Link 2400bps Receiver - 315MHz - WRL-08948 - SparkFun Electronics)](RF Link 4800bps Receiver - 315MHz - WRL-08947 - SparkFun Electronics)](RF Link 4800bps Receiver - 315MHz - WRL-08947 - SparkFun Electronics)](RF Link 2400bps Receiver - 315MHz - WRL-08948 - SparkFun Electronics)](RF Link 4800bps Receiver - 315MHz - WRL-08947 - SparkFun Electronics)](RF Link 2400bps Receiver - 315MHz - WRL-08948 - SparkFun Electronics)](http://winavr.scienceprog.com/example-avr-projects/running-tx433-and-rx433-rf-modules-with-avr-microcontrollers.html)](http://forum.sparkfun.com/viewtopic.php?f=13&t=22948)

3

Thank for the reply languer.

I’ve ordered the WRL-08948; I’ll post back when I get it in the mail.

4

Take a look at [dosman’s last post. It looks like adding a buffer to the data output on the new receiver may do the trick.](http://forum.sparkfun.com/viewtopic.php?f=13&t=22948)

5

WRL-08948 fixed my above problems.

Thank you for all the help.