LG K4 2016 (lg-k130f)

Contributors

 * Brunothedev
 * Mark

How to enter fastboot
Press Volume Down on your device and then plug the cable, you now can use fastboot commands

How to unlock the bootloader
Install mtkclient run: after that:

Development
The device bootloops, fixing that

UART setup and soldering guide
Connecting UART will require you to solder two wires: one wire to ground and the second wire to the transmit pad on the motherboard. Additionally, you will need a USB to TTL module.

To solder the wire successfully, especially for a soldering beginner, it's recommended to find some scrap electronic board to train soldering on and try to solder a wire to the smallest solder pad you can find on the board. To solder a wire to the small UART transmit pad, you will need a small tip for the soldering iron, solder, and a microscope (it doesn't need to be expensive). Flux is also good to have to help the solder flow, but it's possible to solder without it.

Next, find a small wire and strip the wire end open with a knife to reveal strands of small wires inside. Leave just one strand of wire for soldering, and once you have done that, fill the strand with solder.

Once you have tinned the strand with solder, then proceed to solder the strand of wire to the transmit pad, TX0. Take your time to solder; no rush.

When you have successfully soldered the strand of wire to transmit pad (TX0), then connect that wire or also solder the wire to the receive pad (RX) on your USB to TTL module.

Also remember to solder the ground wire :).

For me, the writer for this UART setup and soldering guide section, I used CH341A v1.7 programmer with a voltage selection switch. I used the 1.8V setting.

For further documentation or troubleshooting, refer to the postmarketOS serial debugging wiki: https://wiki.postmarketos.org/wiki/Serial_debugging#Plugging_in_the_cable