docs: Move Mega 2560 information to separate file
Make a more comprehensive document describing the Mega 2560 and FPC breakout board.
This commit is contained in:
Tim Crawford
Jeremy Soller
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babcc970c4
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2414476a66
@ -13,27 +13,12 @@ external USB keyboard or SSH session.
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Requirements:
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- Arduino Mega 2560 compatible board
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- 24 pin flexible printed circuit
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- 24 pin FPC breakout board and cables
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- 0.5mm or 1.0mm pitch, depending on target connector
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- 24 pin FPC breakout board with connectors
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- USB-C cable
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### Configuring the Mega 2560
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If the breakout board did not come preassembled, assemble it before
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starting. This will require soldering.
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1. Connect the breakout board to the Mega 2560
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- Orientation will affect the mapping of GPIO pins
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2. Connect the Mega 2560 to the host
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3. Configure GPIO pin mapping in `parallel.c` based on how it will
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connect to the target parallel port
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- Trace pin 1 on motherboard connector to Mega's GPIO pins
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4. Build and flash the firmware for the Mega 2560
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```
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make BOARD=arduino/mega2560
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make BOARD=arduino/mega2560 flash
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```
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For details on configuring the Mega 2560 and breakout board, see
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[mega2560](./mega2560.md).
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### Setup
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@ -44,10 +29,10 @@ make BOARD=arduino/mega2560 flash
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3. Remove bottom panel
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4. Unplug keyboard cable
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- May require removing keyboard depending on port location
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5. Connect Mega 2560 to host
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- This will create an ACM device at `/dev/ttyACM*`
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6. Ground target to host
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5. Ground target to host
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- Connect USB cable from USB-C port on target to host
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6. Connect Mega 2560 to host
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- This will create an ACM device at `/dev/ttyACM*`
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7. Connect Mega 2560 to target
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8. Start the console
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```
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@ -57,7 +42,7 @@ make BOARD=system76/<model> console_external
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EC logs should now print to the console on the host. This can be tested
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by removing or inserting the AC adapter to trigger a power event.
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To return the Mega to host mode, reset the device.
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To return the Mega 2560 to host mode, reset the device.
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If logs are corrupted, try power cycling the Mega or reseating the cable.
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72
doc/mega2560.md
Normal file
72
doc/mega2560.md
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@ -0,0 +1,72 @@
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# Mega 2560
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The Mega 2560 is the recommended tool for EC flashing and debugging.
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The Mega 2560 is an open-source hardware design by [Arduino] based on the 8-bit
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Atmel ATmega2560. Arduino's official model sells for around 40 USD. Multiple
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clones exist, and can be bought for around 15 USD.
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## Clone compatibility
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Multiple clones of the Arduino Mega 2560 exist. Clones can be used, but must be
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compatible with the Arduino model. Some have replaced the ATmega16U2 chip used
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for USB communication with a CH340G chip. If it does not explicitly state that
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it uses the ATmega16U2, find a different model.
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## FPC breakout board
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A flexible printed circuit (FPC) breakout board is required. It should have:
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- 24 pins with 0.1" (2.54mm) pitch
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- One side with 0.5mm pitch FPC connector (for lemp9)
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- One side with 1.0mm pitch FPC connector (for all other models)
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Depending on the vendor, the connectors may not come soldered to the board (or
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at all). A header block will likely not be be provided, so male breakaway
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headers will need to be purchased separately.
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### Connecting to the Mega 2560
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The FPC board should be assembled so the 1.0mm pitch connector faces up. When
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connected to the Mega 2560, the FPC connector should face away from the Mega
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2560. In this orientation, pin 1 of the FPC connector connects to pin 22 (PA0)
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of the Mega 2560.
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### Connecting to the laptop
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A 24 pin flexible flat cable (FFC) is used to connect the Mega 2560 to the
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laptop. It may be worth buying both a set of standard cables (traces exposed on
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same side at each end) and reversed cables (traces exposed on opposite sides at
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each end). With both, it will always be possible to have pin 1 of the breakout
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board go to pin 1 of the keyboard port.
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The orientation of the FFC traces can be determined by looking at how the
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keyboard connects to its port.
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The laptop keyboard may use a 26-pin connection. Ensure that the FFC is aligned
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so the traces line up with pins 1-24 on the keyboard port.
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A second cable (typically, USB-C) must be used for grounding the target laptop
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to the host system (what the Mega 2560 is connected to).
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## Firmware
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`mega2560/parallel.c` must be modified for the mapping of the keyboard pins to
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the GPIO pins.
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- [Arduino Mega 2560 pin mapping][PinMapping2560]
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Using the orientation described above, pin 1 of the keyboard maps to
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- pin 22 (PA0) of the Mega 2560 when using the 1.0mm pitch connector
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- pin 45 (PL4) of the Mega 2560 when using the 0.5mm pitch connector
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Once the GPIO mapping is updated, the firmware can be compiled and flashed.
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```
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make BOARD=arduino/mega2560
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make BOARD=arduino/mega2560 flash
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```
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[Arduino]: https://www.arduino.cc/
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[PinMapping2560]: https://www.arduino.cc/en/Hacking/PinMapping2560
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