# Troubleshooting

## LED status

### Green LED

- **_Off_**: no power to the module
- **_On_**: module is powered up 

### Red LED (bind LED)

- **_Off_**: program not running or a protocol selected with the associated module not installed
- **_Flash(on=0.05s,off=1s)_**: invalid protocol selected (excluded from compilation or invalid protocol number)
- **_Inverted Flash(on=1s,off=0.1s)_**: module is waiting for a bind event (Bind from channel or Bind in radio GUI) to launch the protocol in bind mode
- **_Fast blink(on=0.1s,off=0.1s)_**: bind in progress
- **_Slow blink(on=0.5s,off=0.5s)_**: serial has been selected but no valid signal is being seen on the RX pin.
- **_Slower blink(on=1s,off=1s)_**: PPM has been selected but no valid signal is being seen on the PPM pin.
- **_Fast double blink(on=0.1s,off=0.1s,on=0.1s,off=0.5s)_**: serial debugging is enabled and is waiting for a serial connection
- **_On_**: Module is in normal operation mode (transmitting control signals).
- **_SOS_**: Module's CPU does not match the minimum requirement of a full 128KB available/good flash. The module won't boot further. This has been introduced after finding out that some module's manufacturers are using wrong components which are causing unexpected behaviors with bad consequences...

## Protocol selection

### Input Mode - PPM

- The protocol/mode selection must be done before the power is applied to the module
- Often the signal is not sent to the module until the transmitter has performed safety checks (like switch and throttle position settings)
- Check that at least one of the protocol selection pins is connected to GND.
- Some radios have an open collector output (Futaba, Graupner...), in this case add a 4.7K resistor between PPM and BATT.

### Input Mode - Serial

- Make sure you have done the serial mods as indicated in the [hardware page for your board](Hardware.md).
- Protocol selection dial must be in the 0 position or leave all 4 selection pins unconnected.
- Often the signal is not sent to the module until the transmitter has performed safety checks (like switch and throttle position settings)
- The protocols/subprotocols names which appear on the OpenTX/er9x/ersky9x radios are only based on the radio firmware version. The module does not send this information. You likely have to upgrade your radio firmware to get all the latest.
  - For ersky9x radios, you can update the protocols list by placing the file [Multi.txt](/Multiprotocol/Multi.txt) at the root of the SD card. This feature is not supported by OpenTX.
  - Even if not listed on the radio you can still access protocols/subprotcols by using their numbers as given on the [Protocol page](/Protocols_Details.md).

## Bind

Make sure to follow this procedure: press the bind button, apply power and then release after the red LED starts flashing. The LED should be blinking fast indicating a bind status and then fixed on when the bind period is over. It's normal that the LED turns off when you press the bind button, this behavior is not controlled by the Atmega328.
For serial, the preffered method is to bind via the GUI protocol page.

If your module is always/sometime binding at power up without pressing the button:
 - Arduino Pro Mini with an external status LED: to work around this issue connect a 10K resistor between D13 and 3.3V.
 - 4in1 module V1 (check 4in1 pictures): to solve this issue, replacing the BIND led resistor (on the board back) of 1.2K by a 4.7K.
 - check that your module case is not pressing the bind button.


FrSky & SFHSS & Corona & Hitec bind issues, heratic moves and telemetry losses are ususally due to Option=fine frequency tuning not set properly. This value is different for each RF module and some RXs. To determine this value check this [Frequency Tuning page](/docs/Frequency_Tuning.md).

## Report issues

You can report your problem using the [GitHub issue](https://github.com/pascallanger/DIY-Multiprotocol-TX-Module/issues) system or go to the [Main thread on RCGROUPS](http://www.rcgroups.com/forums/showthread.php?t=2165676) to ask your question.
Please provide the following information:
- Multiprotocol code version
- TX type
- Using PPM or Serial, if using er9x or ersky9x or OpenTX the version in use
- Different led status (multimodule and model)
- Explanation of the behavior and reproduction steps
