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I've bought a Realtek RTL2832 DBV for my RPI to read 433 mhz data and a transmitter HM-T433. I can successfully receive messages from two 433mhz remotes with the rtl_433 utility, but when I try to send any data I am always getting readings like

[00] {0} 00 : 00000000

I've tried sending the data trough the ninjablock utility, RCSwitch, pilight, custom code and a lot more of other possibilities but all readings from rtl_433 are bits of 0.

Is this normal? Is there something wrong with the transmitter (how can I check that)? Am I not reading the data correctly?

Ali Cornea
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2 Answers2

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I think you are mixing up signal moldulations.

HM-T433 uses FSK (Fequency Shift Keying).

Most applications in 443MHz use ASK (Amplitude Shift Keying) and of those most use OOK (On/Off Keying). That means they either send a signal with constant amplitude and frequency for "1" and don't send anything at all for 0.

RTL2832 is capable of doing both FSK and ASK. But you have to configure it correctly for your application. The rtl_433 utility is fitted for ASK/OOK so your transmitter does not match. You will need to find another utility that uses FSK.

Try GQRX to find out if you receive the signal at all.

user49015
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This site says that HM-T433 is a perfect match for HM-R433. The other one is most likely a just a demodulator/TV tuner. Do you have receive modules?

EDIT: TRY FLIPPING THE TX/RX PINS

Aloha
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