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I have an RF 443.92 MHz transmitter and the receiver, the model is TWS-DS-3 and I'm trying to understand how does it works. There are 4 pins (GND, Data In, Vcc, ANT), I'm going to wire the Vcc on a 5V power (of a Raspberry Pi), the GND on the GND and the Data In on a digital output GPIO that provides 3.3v logic level. What happens when I set the Data In pin to the HIGH state ? It will set the receiver Data Out to the HIGH state too after transmitting ? Do I need any resistor to limit the current between the GPIO data pin or in the Vcc pin ?

Update: I just plugged the receiver RWS-375-6 into an Arduino with the "Linear Out" pin on an analog pin and the TWS-DS-3 (transmitter) I plugged into a Raspberry Pi, when I set the pin to a HIGH state the output on the analog output of the Arduino is this:

enter image description here

The peaks are when I set the GPIO pin (which is connected into the Data In of the transmitter) to HIGH state, sleep 100ms and then turn it LOW and wait for 1 second.

If someone is also interested, here is the wiring I've done on the Raspberry Pi:

enter image description here

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    \$\begingroup\$ It's not good practice to connect 3.3V and 5V devices directly together, even if you're only going from the 3.3V -> 5V direction. Having said that, the datasheet you have there suggests that you can power the transmitter from 3.3V, so you should just do that, assuming that you can find the 3.3V VCC on the raspi board. \$\endgroup\$
    – pjc50
    Commented Aug 20, 2012 at 10:55
  • \$\begingroup\$ I see, I just assumed 5V operating level because the datasheet doesn't shows a 3.3v level on the "Electric Current" item, it just shows the current for 5V, 9V and 12V. Thanks. \$\endgroup\$
    – Tarantula
    Commented Aug 20, 2012 at 12:22
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    \$\begingroup\$ @Tarantula - But the (bad) datasheet says it will operate from as low as 1.5 V, so 3.3 V is OK, you'll just have less range than with 5 V. In any case you'll be assured that the RPI's data is received correctly by the transmitter. \$\endgroup\$
    – stevenvh
    Commented Aug 20, 2012 at 15:09

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Since the datasheet mentions ASK/OOK (Amplitude Shift Keying / On Off Keying) I'd say the receiver (assuming compatible type like this) will output what goes in, yes. It's a very basic module. It looks like it is designed to be used with an encoder IC like a remote control, although you don't have to do this.

It's very unlikely you will have to limit current to the pins, but a series input pin resistor (e.g. 1kΩ) won't hurt if you want to be as safe as possible.

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You are trying to connect 3.3 v logic level to 5 V level. Before joining the two, first check if the pin of your Raspberry Pi is 5v tolerant or not otherwise you have to use level shifter to operate it correctly.

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    \$\begingroup\$ The RPi doesn't see the 5V; it only has output to the module. The datasheet is next to useless, though, and doesn't say if the 3.3 V input is enough to be seen as a logic high level. \$\endgroup\$
    – stevenvh
    Commented Aug 20, 2012 at 15:05
  • \$\begingroup\$ Thanks for the advice, I wired it on the 3.3v pin of the Raspberry Pi, see my updated image. \$\endgroup\$
    – Tarantula
    Commented Aug 21, 2012 at 1:54

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