How does BAT_EN pin work?

[giannoug]

I can't seem to understand how BAT_EN (IO12) works. I have a board versioned 2022-5-22 V1.1. Can you explain?

Both do nothing at all, battery is controlled only with switch:

  pinMode(BAT_EN, OUTPUT);
  digitalWrite(BAT_EN, LOW);

same for

  pinMode(BAT_EN, OUTPUT);
  digitalWrite(BAT_EN, HIGH);

[LilyGO]

Hello. When only battery power is available. You need to enable BAT_EN for power supply

[giannoug]

On battery power, battery is only controlled with the switch, digitalWrite(BAT_EN, LOW); and digitalWrite(BAT_EN, HIGH); do nothing 🤔

[LilyGO]

digitalWrite(BAT_EN, LOW); Unable to start A7670

[giannoug]

digitalWrite(BAT_EN, LOW); Unable to start A7670

Doesn't make sense according to this:

[LilyGO]

This circuit is in good working order. Can you elaborate on why it doesn't make sense?

[giannoug]

When the board runs on battery power, the power can be cutoff using the BAT_EN (IO12) pin if I understand correctly. It doesn't work in my case

[gasagna]

digitalWrite(BAT_EN, LOW); Unable to start A7670

This is correct, as I demonstrate here for a slightly different dev board and a slightly different problem. Basically, if BAT_EN remains low, the simcom module cannot be woken up while on battery power, e.g. with a pulse on the POWERKEY. While attached to the USB, this pin does nothing.

The nice thing is that if you keep the BAT_EN pin low, the simcom module never wakes up automatically. This is nice in low-power applications, when you might only want to turn on the modem every hour of so to send data to a server.

These are great boards with lots of functionality, but I wish the documentation was more extensive

[gasagna]

When the board runs on battery power, the power can be cutoff using the BAT_EN (IO12) pin if I understand correctly. It doesn't work in my case

I do not think that is the intended behaviour (at least on my board with a A7608). The ESP32 keeps working, regardless of BAT_EN. It's the simcom module that depends on it.

[giannoug]

@gasagna I agree they are good boards, but documentation is all over the place.

For example check this: https://github.com/Xinyuan-LilyGO/T-A7670X/blob/main/examples/new_version/Arduino/battery_voltage/battery_voltage.ino#L17

Why does this sketch "enable battery" when it's not going to use the A7608?

Also check the pinout on the homepage: It clearly shows that the 18650 is enabled with pin 12.

Also, there is a battery voltage sketch for V1.0 boards but that functionality is missing from these boards... https://github.com/Xinyuan-LilyGO/T-A7670X/blob/main/examples/new_version/Arduino/battery_voltage/battery_voltage.ino

@LilyGO Lastly let's not forget this product costs ~$50. Two of the "advertised" features do not work.

[LilyGO]

Thank you for the suggestion and the @gasagna instructions. We will optimize the instructions. battery_voltage.ino example is for easy porting.

[LilyGO]

From the schematic, we know that BAT_EN(IO12) controls whether BAT is on or off. When using only battery power VBUS is not. BAT will supply power to A7670. So BAT_EN(IO12) is the on/off of BAT to control the power of A7670.