turn off when battery is low (#186)

* turn off when battery is low

switch off at 3.5V. remove python bq and fusb drivers

* run ruff

* update comment

drivers/tildagon_power/bq25895/bq25895.c

@@ -42,13 +42,13 @@ static void write_scaled( bq_state_t* state, scaled_register_t scaledregister, f
  * @details reset then setup 500mA Iin limit, boost disabled, charging enabled,
  * ADC at 1Hz, disable unused features and disable watchdog to reduce interruptions
  * charge current limit to be 0.85C for the 1800mAh and 0.77C for 2000mAh batteries
- * termination and precharge current to 64mA. min Vbat 3.5V
+ * termination and precharge current to 64mA. min Vsys to 3.0V
  * @param state pmic object
  */
 void bq_init( bq_state_t* state )
 {
     write_bits( state, register_reset, 1 );
-    uint8_t write_buffer[5] = { 0x02, 0x60, 0x1A, 0x18, 0x00 };
+    uint8_t write_buffer[5] = { 0x02, 0x60, 0x10, 0x18, 0x00 };
     mp_machine_i2c_buf_t buffer = { .len = 5, .buf = write_buffer };
     tildagon_mux_i2c_transaction( state->mux_port, ADDRESS, 1, &buffer, WRITE );
     write_buffer[0] = 0x07;