RadioMaster RP1 ELRS receiver: specs and pinout
13 x 11 x 3 mm ExpressLRS 2.4 GHz receiver that outputs the CRSF serial protocol on its TX and RX pads.
Specs
| Spec | Value | Source |
|---|---|---|
| Frequency band | 2400 MHz to 2483 MHz | source Specifications (p.1) |
| Input voltage | 5V | source Specifications (p.1) |
| Receiver protocol | CRSF | source Specifications (p.1) |
| Pre-installed firmware | ExpressLRS v3.0 | source Specifications (p.1) |
| MCU | ESP8285 | source Specifications (p.1) |
| RF chip | SX1281 | source Specifications (p.1) |
| Size | 13 x 11 x 3 mm | source Specifications (p.1) |
| Weight | about 2.2 g (the manual's two columns disagree on whether the antenna is included) | source Specifications (p.1) |
| Included | RP1 receiver, 65 mm UFL 2.4 GHz T-antenna, user manual card, 4 silicone wires | source Includes (p.1) |
Power
| Value | Source | |
|---|---|---|
| Supply | 5 V | source Specifications (p.1) |
Pinout
Pad labels come from the maker's user manual. The manual does not give the serial signal voltage.
| Pin | Function | Voltage | Notes | Source |
|---|---|---|---|---|
| 5V | Power input | 5 V | Pad labelled 5V on the board | source Board diagram (p.1) |
| GND | Ground | Pad labelled with a ground mark on the board diagram | source Board diagram (p.1) | |
| TX | Serial transmit pad | Signal voltage not given in the manual | source Board diagram (p.1) | |
| RX | Serial receive pad | Signal voltage not given in the manual | source Board diagram (p.1) | |
| u.Fl | Antenna connector | Fit the antenna before use | source Board diagram (p.1) | |
| BOOT | Firmware upgrade button | Short it to GND with a metal object while powering on | source Board diagram (p.1) |
Build with it
Project ideas for the RadioMaster RP1 ELRS receiver. Each link opens Soldr with the prompt filled in; Soldr assigns the pins, checks power and shows how to wire every part.
- Channel viewer: Power the receiver's 5V pad from the board's USB 5 V pin; the manual gives no current figure, so do not power it from a higher-voltage battery. The manual does not state the signal voltage of the TX pad, so check it with a multimeter before joining it to the 3.3 V ESP32 RX pin. The transmitter must run ExpressLRS 2.4 GHz. Bench only, no motors or propellers connected. Learning project.
- Stick input recorder: The Pi 5 header has a 5 V pin for the receiver. The manual does not give the serial signal voltage, so measure the TX pad before connecting it to the Pi's 3.3 V RX pin. Bench only, no motors or propellers connected. Learning project.
- Serial monitor over USB: Small board powered over USB, which gives the receiver its 5 V. Check the TX pad voltage before connecting it to a 3.3 V input pin. Bench only, no motors or propellers connected. Learning project.
Common mistakes
- Powering it from anything but 5 V; the manual gives 5V as the input voltage (source: link, Specifications p.1).
- Binding with the binding phrase left commented out. The manual says the binding phrase option must be uncommented in the device options; then turn the transmitter off, power the receiver on and off 3 times until the LED double-blinks, and press Bind in the ExpressLRS Lua script (source: link, Traditional binding p.1).
- Leaving the flight controller port in its default mode. The manual says the UART connected to the receiver must be set to Serial RX in the Ports tab, and the receiver provider set to CRSF (source: link, Configuration p.1).
Not covered by the official source
- The manual gives no current draw, no serial signal voltage and no UART baud rate for CRSF.
- The manual lists the RF chip as SX1281 in the English column; the Chinese column of the same sheet appears to differ, so the chip is shown as written in the English column.
- Weight: the manual's English column says 2.2 g with antenna and the second column says 2.2 g without antenna, so the antenna is not confirmed as included.
Sources
- link (RP1 Receiver User Manual, maker's own file)