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Wireless La Crosse Temp/RH sensor with RFM69Pi


(Paul Raymond) #1

I have an emonPi with a RFM69Pi at 433Mhz and the La Crosse outdoor temperature and humidity sensor (TX141TH).
And was wondering if I could read the temp and RH% using the RFM69Pi.
I used minicom at 38400 on /dev/ttyAMA0 and get this every 10 seconds

0,11,20,0,0s
-> 4 b
0,11,20,0,0s
-> 4 b
Which does not matchup with the actuals temp and RH. Plus the data comes in every 10 seconds, and the LaC sensor reports every 58-60mseconds.

Do you think I can read the sensor data using the RFM69Pi on my emonPi?


(Paul) #2

I’m guessing you mean an emonbase? All emonPi’s have an rfm69 RF module on board, but I think you are referring to a Raspberry Pi with an add on RFM69Pi, is that right? The “emonPi” at the command prompt is misleading, ideally it should be emonBase or emonSD.

This looks like emonhub transmitting the time (11:20am) out to a emonGLCD, followed by a confirmation from the RFM69Pi that 4 bytes were transmitted.

I do not know what protocol or format etc that device transmits but I would be very surprised if it uses JeeLib which is how the data is expected to arrive by the RFM69Pi, You may be able to find or write some code to get it working if the hardware is companionable, but it’s unlikely to “just work” i’m afraid.


(emjay) #3

@raymop,

AFAIK, that series of environment monitors use OOK modulation, not the FSK configured in the standard code. The RFM69CW module is capable of receiving OOK, but requires a very different initialisation and driver code. The OOK related calls in the standard JeeLib driver are stubbed out for the RFM69 - these sections do not port across from the earlier RFM12B driver.
You might like to look at SevenWatt’s work - OOK on Hope mixed FSK/OOK modules. He successfully receives and decodes a variety of OOK-based protocols.
It may be possible to switch the radio between standard FSK traffic and OOK for your environment if you are prepared to miss samples once in a while - the timers in the sensing nodes are not perfect, so sooner or later will drift enough that overlapping demands for reception. The radio module is Simplex i.e. can only listen on one channel in one modulation style at a time.