mirror of
https://xff.cz/git/pinephone-keyboard/
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64 lines
2.7 KiB
Text
64 lines
2.7 KiB
Text
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Pinephone keyboard firmware
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---------------------------
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Current firmware implementation relies on polling the key matrix
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once every 20ms.
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The controller has ability to detect change on
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the row input port, so it is possible to ground all column GPIOs
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enable pull-ups on row GPIOs, and wait on change on the row GPIOs.
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This only works when no key is pressed, otherwise one pressed
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key would mask changes in the state of other keys on the same row.
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This is good to achieve large power savings by not polling when
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we detect that no keys are pressed, which is the normal state
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of all keys.
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Firmware thus switches between two modes of operation:
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- idle - when no keys are pressed, columns are grouded, rows are pulled up
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and the controller only reacts on the change in the row GPIOs
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- when the change is detected, it switches to active mode
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- active - when a key is pressed, the firmware performs periodic
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full scans of the keyboard matrix, to determine what keys
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are actually pressed
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- when no keys are pressed anymore it switches to idle mode
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It is possible to power down the CPU and all peripherals in idle mode
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via PCON.PD bit and only wait to be woken up by GPIO change interrupt.
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(or I2C interrupt)
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My prototype keyboard has Z key always pressed due to some HW bug,
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so this method of switching to idle mode and powering down the
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controller will not work on my keyboard. The firmware implements
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in this case a always active polling mode.
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Observations
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------------
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- Power consumption in polled mode is about 20mW.
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- I2C interrupts don't always wake from power down. (maybe the wakeup
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only works on the I2C address match condition, as stated in the manual
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so we need to ensure that the controller is not put back to powerdown
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mode, until the I2C transaction finishes)
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How to flash the firmware
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-------------------------
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- If you have original firmware, it's enough to just run the flashing tool.
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- If you have this firmware, you can enter flashing mode by pressing
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FN + PINE + F
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- If you have broken firmware, you need to short P90 (7th test pad from the left)
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to GND and power cycle the keyboard controller.
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- Power cycling requires powering down the connected pinehone and maybe
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ensuring VOUT is disabled on the kb charger (can be done via I2C,
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or by pressing the charger key)
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- You need to keep P90 shorted until the flashing is complete.
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- You can insert the flasing USB cable safely even with 5V/VBUS wire
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connected regardless of whether the charger's VOUT is enabled or not.
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- Flashing tool is configured by modifying the source code for now.
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If your firmware grows, don't forget to increase the flashing area
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size. Currently it's set to 0x2000 - 0x2600.
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