ELRS Receiver 2.4G-16pwm-vario-500mw

# ELRS receiver 2.4G-16pwm-vario-500mw
**Based on the expressLRS open source project: high performance, high refresh rate, high sensitivity, and ultra-long-distance remote control protocol. **
*This hardware open source address is https://oshwhub.com/vinvaa/elrs-rxPWM-vario-500mw, expressLRS exchange group: 1035943784*

![elrs receiver 2.4g 16pwm vario 500mw back view.png]
## Features
- esp32-pico-d4 high performance main control
- Use E28-2G4MxxS mature and reliable RF module
- Size: 34mmX21mm
- Working voltage: 5v
- Output channels: up to 16 PWM
- Telemetry return power: maximum support 500mw
- Altimeter vario return, using high-precision barometer SPL06
- Support 8S (33V) battery voltage vbat return
- Can switch output CRSF protocol, can also be switched to transmit high-frequency head
- WiFi web page to set pwm output, and update firmware
- IC components single-sided layout, easy to make

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## Production
### Hardware production
1. Use the gerber file to Jiali Chuang PCB [first get a free coupon](https://www.jlc.com/newOrder/#/collectCoupons ) and then [one-click order for 5 samples](https://www.jlc.com/newOrder/#/pcb/newOnlinePlaceOrder)
2. Open the bom.html interactive web list, purchase components and place them according to the diagram.
3. You can use a 10-yuan "PTC heating table/LED desoldering table" for soldering: pre-tin the pad with a soldering iron (or apply tin paste), place the components according to the interactive ibom, move the PCB to the heating table and heat it for a while until the tin melts and the soldering is done. (Reduces the difficulty for novices)
4. Check whether the pins are tinned or not, and use a soldering iron + flux to treat them.
5. Use a multimeter to measure whether 5V/3.3V is short-circuited to the ground, and measure whether the adjacent pins of ESP32 are short-circuited according to the ibom diagram.

*tips: 1. The back pad is fully compatible with the 20s27s pins. If you use 12s, pay attention to the dotted mark; 2. Whether the barometer is soldered determines the number of PWM channels, see [Firmware section](#gujian)*

### Burning preparation
1. Prepare a USB-TTL tool, such as one based on the CH340G chip
2. Connect TTL's TX and RX to the receiver's PWM15 and 16 output pins (respectively multiplexed as RX and TX functions)
3. Press and hold the BOOT button (or short PWM6 to GND), and then connect 5v and gnd respectively
|USB-TTL | Receiver|
|------------|-----------|
|5V | 5V |
|GND | GND |
|TX | RX/pwm16 |
|RX | TX/pwm15 | 4.
Insert the TTL tool into the computer

### Firmware selection{#gujian}
1. No barometer-
E28-2G4M12s: 16mw telemetry feedback, 16 pwm channel output
Custom firmware `DIY_2400_RX_ESP32_E2812S_16PWM`
compatible with the official native firmware `Generic ESP32 True Diversity 16xPWM 2.4Ghz RX`
- E28-2G4M27S: 500mw telemetry feedback, occupying ~~ch15, 16 pins ~~ no output
Custom firmware `DIY_2400_RX_ESP32_E2827S_500mw_14PWM`
2. With barometer
- E28-2G4M12s: Custom firmware `DIY_2400_RX_ESP32_E2812S_vario_14PWM`, occupying ~~ch13-14 pins ~~ no output
- E28-2G4M27S: Custom firmware `DIY_2400_RX_ESP32_E2827S_500mw_vario_12PWM`, occupies ~~ch13-16 pins~~no output

| RF module | No barometer | PWM output | | With barometer | PWM output |
|-----------------|------------------|----------------|---| --------------|------------------|
| E28-2G4M12s | Custom firmware DIY_2400_RX_ESP32_E2812S_16PWM | PWM1-16 | | Custom firmware DIY_2400_RX_ESP32_E2812S_vario_14PWM | PWM1-12, 15-16; 13-14 no output |
| E28-2G4M27S |Custom firmware DIY_2400_RX_ESP32_E2827S_500mw_14PWM | PWM1-14 | | Custom firmware DIY_2400_RX_ESP32_E2827S_500mw_vario_12PWM | PWM1-12 |



### Write firmware to device {flash}
Blank master controller first time burning firmware
*Take the receiver of the E28-2G4M12S RF module as an example. Since it does not have a barometer soldered on it, it is compatible with the official native firmware `Generic ESP32 True Diversity 16xPWM 2.4Ghz RX` and can be used directly after flashing. For other modules or when using a barometer, you can also flash it according to this example, and then use the [update/upgrade](#update) method to update the corresponding correct firmware. *
1. Online flashing via webpage: simple, convenient and fast
- Open [web flasher](https://pkendall64.github.io/elrs-web-flasher/):https://pkendall64.github.io/elrs-web-flasher/
- Select the device page:
- Select Version 3.2.1 or above;
- Select DIY Device or Generic target as Vendor;
- Select 2.4GHz Receive as Device Type;
- Select `Generic ESP32 True Diversity 16xPWM 2.4Ghz RX` as Device Model
- Next, go to the Option settings page:
- Enter the binding phrase by yourself;
- Select Serial UART as Flashing Method;
- Next, go to the Flashing steps:
- Press and hold the boot button on the receiver and then insert the usb-ttl tool:
- Click connect, and select the serial port (com**) of the device on the pop-up page
- Once the connection is successful, start flashing the firmware to the device
- The window below scrolls the command information. Wait 3-5 minutes for the flashing to complete.

2. Ground station method: simple and convenient. Although it takes a long time to load the plug-in for the first time, it is very fast afterwards.
- Download expresslrs configurator [official ground station] (https://github.com/ExpressLRS/ExpressLRS-Configurator/releases) and install
https://github.com/ExpressLRS/ExpressLRS-Configurator/releases
- Select the device:
- Select Version 3.2.1 or above;
- Select DIY Device or Generic target for Vendor;
- Select 2.4GHz Receive for Device Type;
- Select `Generic ESP32 True Diversity 16xPWM 2.4Ghz RX` for Device Model
- Parameter setting page below:
- Binding phrase, enter it by yourself; others can be left as default
- Click Compile Building. The first time you use the newly installed ground station, you need to wait 1-3 hours for the dependent software to be automatically installed. During this period, it will report red errors repeatedly and you need to retry several times until you see a green **[ successe]**
- Press and hold the boot button on the receiver and then insert the USB-TTL, then click Flashing, it will be completed in 2-5 minutes

*tips: Go to the Penguin Chat Group "ExpressLRS Open Source Exchange Group: 1035943784, or the "Multi-protocol Module Exchange" group file. There is a Chinese version of the ground station. It is faster to connect to the domestic server for the first time to use the installation environment. *

3. Flashing with SpeedyBee APP: can only be done via WiFi, not suitable for first flashing of blank chips-
Download and install SpeedyBee, open- In
the bottom navigation bar, click the second icon toolbox, which contains the elrs configurator-
Select brand-device-name, binding password, etc.

4. VS CODE method: complex but reliable, convenient for modifying custom pins and functions-
Download and install vs code, download and install git tool software-
Search and install the platform extension plug-in in vs code-
Clone the expressLRS open source project and open the project/src directory-
Open the `user_defines.txt` file, set the binding password "default ExpressLRS binding phrase", and replace the text in quotation marks-
Delete the first character # of `#-DRegulatory_Domain_ISM_2400`, and the others can be default-
Click the platform alien-like icon on the left panel- Select
and click `Generic ESP32 True Diversity 16xPWM 2.4Ghz RX`
- Click build. For the first time, you need to wait for 1-3 hours to automatically install the dependent software. During this period, it will repeatedly report red errors and need to retry several times until you see [successe]
- Press and hold the boot button on the receiver and insert the usb-ttl, then click Flashing, which will be completed in 2-5 minutes
. 5. ESP32 FLASH Download tool, or Node MCU Pyflasher tool.
Omitted

### Firmware update and upgrade{#update}
1. After the receiver enters WiFi mode, connect to WiFi and open the 10.0.0.1 webpage update function to upload the .bin firmware upgrade
- After the wifi module can be connected to the transmitter, select receive wifi in the remote control lua menu
- After the receiver is powered on for 60 seconds, it will enter WiFi mode without connecting to the flight control
- The green light flashes quickly in WiFi mode
2. Use the ttl tool to connect to the computer and flash in various ways as for the first flash, which is suitable for repairing bricks
3. In WiFi mode, use webpage flasher, ELRS ground station, vscode, speedybee application and other tools to upgrade over the air with WiFi
4. If the device is already installed and connected to the flight controller, you can use tools such as web flasher, ELRS ground station, vscode, etc. to use BetaflightPassthrough [not available when the receiver is used as PWM output]

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## Usage

**elrs users must read the [Official User Guide](https://www.expresslrs.org/ "Official Wiki")** https://www.expresslrs.org/
### Indicator
The status displayed by the receiver with RGB LED is as follows:

| Indicator Indicator | Status |
| --- | --- |
| Rainbow color-changing breathing effect | Startup |
| Green heartbeat | Web update wifi mode enabled |
| Slow flash 1 time/s | Waiting for connection from transmitter |
| Red flash 5 times/s | No radio chip detected |
| Orange double flash then pause | Enable binding mode |
| Orange triple flash then pause | Connected to transmitter TX, but model match id does not match |
| Solid color monochrome | Connected to transmitter, color indicates packet rate |

### Set channel mapping and failsafe value
Enter WiFi mode, open the 10.0.0.1 webpage, select the elrs channel ch mapped to each pwm pin header on the model page, and set the failsafe value, output reverse, output signal frequency mode, etc.


### View the return altimeter and voltage calibration
opentx/edgetx open source remote control setting page, the second to last page: telemetry. Click 'discover new sensor' to view the return information.

### Switch crsf output
- Enter WiFi mode, open 10.0.0.1/hardware.html after connecting your phone or computer
- Change to CRSF output [rx and tx wiring use the pin headers where pwm15 and 16 are located]
Delete the characters in the `pwm_outputs` box, and fill in the first two lines of serial_rx and serial_tx with the values ​​3 and 1
- Restore pwm output
Restore the characters in the `pwm_outputs` box