[Bug]: LoRa modem of the Heltec HT-CT62 turns deaf after voltage dips

[dm5tt]

Category

Other

Hardware

Other

Firmware Version

2.5.20

Description

Hey All!

I've see an interesting effect on my Heltec HT-CT62:

If the voltage dips <3V (almost empty battery on a solar station) during TX for a very short time the modems can end up in a zombie state with not being able to receive anything anymore. It stops sending RX interrupts but still answers to SPI stuff.

Did anyone else see this behavior? Maybe we need a LoRa watchdog that resets if it's quiet for an abnormal time.

Best regards!

Relevant log output

[dm5tt]

Idea: We are waking up to read the battery voltage evey few seconds anyway. This might be a good chance to also check for the LoRa status bis if there's something faulty.

(SX1262 datasheet)

If yes -> Reset device.

I implemented this for now for testing. Not that beautiful.. but better than nothing.

if (deviceRunning) {
    uint8_t status[3] = {0x00, 0x00, 0x00};
    
    spiLock->lock();
    digitalWrite(LORA_CS, LOW);
    SPI.transfer(0x17); /* GetDeviceErrors */
    status[0] = SPI.transfer(0x00); /* Status */
    status[1] = SPI.transfer(0x00); /* OpError */
    status[2] = SPI.transfer(0x00); /* OpError */
    digitalWrite(LORA_CS, HIGH);
    spiLock->unlock();
    
    LOG_INFO("SX1262 Status register: 0x%x 0x%x 0x%x", status[0], status[1], status[2]);

    /* 0xd2/d4 0x00 0x00 is the standard status if everything is working */
    if (status[1] != 0x00 || status[2] != 0x00) {
        LOG_ERROR("Error bit in GetDeviceError is set. Restarting device.");
        ESP.restart();
    }
}