Flashing the bootloader

February 27, 2021 · View on GitHub

If you bought the Torn Keyboard kit the ATmega328P has already been programmed, otherwise if you purchased your own components you need to follow this section of the guide.

This guide shows you how to use an Arduino Uno or an USBasp (on Linux / Windows) to program the keyboard. You can use other ISP programmers that are supported by avrdude.

You can check the troubleshooting guide if you have problems programming the bootloader.

Downloading the bootloader

Download the USBaspLoader source code from https://github.com/rtitmuss/USBaspLoader/tree/torn by clicking on the green Code button and then on Download ZIP. Unzipp the files.

You may need to modify the PROGRAMMER setting in Makefile.inc if you are using a different ISP programmer or OS. The next sections will skim over what to edit in case you are using an Arduino or a USBasp.

Arduino Uno as ISP

First you need to program the Arduino Uno as an ISP, as described in Load the Sketch at https://www.arduino.cc/en/Tutorial/ArduinoISP#toc5.

Wiring the programmer

You can use an Arduino Uno to program the AMegta328P with the ISP header on the right PCB. You need to connect the following pins:

Arduino Uno	Torn Keyboard
ICSP Pin 1 - MISO	ICP Pin 1 - COL4
ICSP Pin 2 - +Vcc	ICP Pin 2 - +5V
ICSP Pin 3 - SCK	ICP Pin 3 - COL3
ICSP Pin 4 - MOSI	ICP Pin 4 - COL5
ICSP Pin 5 - Reset	-
ICSP Pin 6 - Gnd	ICP Pin 6 - GND
Digital Pin 10	ICP Pin 5 - Reset

The Arduino Uno board needs a 10µF electrolytic capacitor connected to RESET and GND with the positive (long leg) connected to RESET. The capacitor has to be placed after the programmer board has been loaded with the ISP sketch.

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Flashing

You may need to change the path to your Arduino in the Makefile.inc. Replace the path in line 41 /dev/cu.usbmodem* with your own.

41:     PROGRAMMER = -c avrisp -P /dev/cu.usbmodem* -b19200

Make sure to save your changes before continuing.

Navigate to your unzipped USBaspLoader-torn folder and open a terminal window at that location. You can now flash the bootloader using:

    make
    make flash
    make fuse

Once the bootloader has been flashed to the board, disconnect the Arduino Uno.

USBasp as ISP on Linux

This section has been tested on Ubuntu Desktop version 20.10. If you don't have Ubuntu installed, you can run it from a bootable USB stick without touching your current OS.

Installing the required packages

Open a new Terminal window
run sudo add-apt-repository universe, press Enter when prompted.
run sudo apt-get update
run sudo apt-get install avr-libc binutils-avr gcc-avr avrdude make, press Y when prompted

Testing your USBasp

Plug the USBasp into your computer. Connect the ribbon cable between your USBasp and the ISCP header on your keyboard. Make sure that the ribbon cable notch faces the right way.

Run avrdude -c usbasp -p atmega328p in your Terminal.

If everything is working you should get a message similar to this one:

    avrdude: AVR device initialized and ready to accept instructions

    Reading | ################################################## | 100% 0.00s

    avrdude: Device signature = 0x1e950f (probably m328p)

    avrdude: safemode: Fuses OK (E:FC, H:D0, L:D7)

    avrdude done.  Thank you.

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Flashing

Go into your previously downloaded and unzipped USBaspLoader-torn folder and edit Makefile.inc. Uncomment Line 40. Comment out Line 41.

39:     # PROGRAMMER = -c pony-stk200
40:     PROGRAMMER = -c usbasp
41:     # PROGRAMMER = -c avrisp -P /dev/cu.usbmodem* -b19200

Make sure to save your changes before continuing.

Navigate to your unzipped USBaspLoader-torn folder and open a terminal window at that location. You can now flash the bootloader using:

    make
    make flash
    make fuse

Once the bootloader has been flashed to the board, disconnect the USBasp.

USBasp as ISP on Windows

This section has been tested on Windows 10 version 20H2.

Installing the required programs

If you don't have QMK MSYS already installed on your computer, go HERE and install the latest version. Follow the Get Started section and come back here when you are done. You will also need QMK MSYS later if you want to create your own keymap.

Make sure QMK MSYS is installed.
Download Zadig. You will need this program to install the correct driver for your USBasp on Windows.
Plug your USBasp into your computer.
Start Zadig and select List all Devices under Options.
You should now be able to select USBaspin the drop down menu.
Make sure WinUSBis selected as replacement driver.
Click on Replace Driver to start the progress and wait until it's done.
Close Zadiq. Unplug your USBasp.

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Testing your USBasp

Plug the USBasp into your computer. Connect the ribbon cable between your USBasp and the ISCP header on your keyboard. Make sure that the ribbon cable notch faces the right way.

Open QMK MSYS and run avrdude -c usbasp -p atmega328p.

If everything is working you should get a message similar to this one:

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Flashing

Go into your previously downloaded and unzipped USBaspLoader-torn folder and edit Makefile.inc. Uncomment Line 40. Comment out Line 41.

39:     # PROGRAMMER = -c pony-stk200
40:     PROGRAMMER = -c usbasp
41:     # PROGRAMMER = -c avrisp -P /dev/cu.usbmodem* -b19200

Make sure to save your changes before continuing.

Navigate to your unzipped USBaspLoader-torn folder by typing cd C:/Users/YOURUSERNAME/Downloads/USBaspLoader-torn in QMK MSYS. Change the path according to your own and press Enter.

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You can now flash the bootloader using:

    make
    make flash
    make fuse

Once the bootloader has been flashed to the board, disconnect the USBasp.