Modify power supply of Bluno Beetle motherboard
By checking the schematic diagram, we can see that there are two LDO power chips on Bluno Beetle motherboard (VIN to 5V, and 5V to 3.3V). Bluetooth chip works on 3.3V, and ATMEGA328p chip on 5V (actually the working voltage of the chip is 1.8V~5V). Our lithium battery is 3.7V, so we can directly use lithium battery to power AEMEGA328p chip, changing the original 5V-3.3V to 3.7V-3.3V (feasible after test). Remove D1 diode on the schematic program, and connect the output power of our lithium battery directly to the 5V pin of Bluno Beetle motherboard (in fact, the 5V power line is changed to 3.7V), as shown below:
The corresponding place of diode on motherboard is shown below:
Note when dismantling, use electric soldering iron to remove one pin of diode, and then use tweezers to unceasingly fold the other pin of diode to make it facture naturally, as shown below:
Note: after removing the diode, it is impossible to download program to motherboard by inserting USB, as you switch it off.