pinephone-keyboard/README.i2c-intf
2021-06-19 21:15:38 +02:00

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I2C interface to the firmware
-----------------------------
To control the operation of the keyboard's firmware, the firmware
exposes some "registers" that the user can read/write using the
two kinds of I2C transfers.
1) set values of consecutive block of registers starting from REG_ADDR:
START TX(DEV_ADDR+WR REG_ADDR [REG_DATA REG+1_DATA REG+2_DATA ...]) STOP
2) read values of consecutive block of registers starting from REG_ADDR:
START TX(DEV_ADDR+WR REG_ADDR) STOP
START TX(DEV_ADDR+RD) RX(REG_ADDR [REG_DATA REG+1_DATA REG+2_DATA ...]) STOP
Device address is 0x15.
Registers
---------
0x00: Device ID1 (0x4b)
0x01: Device ID2 (0x42)
0x02: Firmware revision
0x03: System configuration
bit 0: disable KB scanning (1: scanning disabled, 0: scanning enabled)
bit 1: poll mode
1: don't rely on row change detection, poll the matrix periodically
(prevents MCU power down)
0: power down the MCU when no key is pressed, and rely on change
detection on row inupts to wake the MCU up
bit 2: enable USB debug interface
1: enabled
0: disabled
0x10: Keyboard data for column 1
...
0x0b: Keyboard data for column 12
0x0c: CRC8 of keyboard data from 0x10-0x0b
0x70: Flashing mode unlock key
(writing 0x46 to this register unlocks the flashing mode.)
0x71: Flashing control
Writing various commands to this register makes the MCU execute them,
if the MCU is not executing the previous command. Available commands:
0x52 - read a block of data from code ROM
0x57 - write a block of data to code ROM
0x45 - erase the code rom memory block (128B)
0x43 - confirm the validity of the firmware and enable redirection
to it from the main app (this redirection is automatically
disabled before executing the 0x57 command)
0x7d: target address low byte
0x7e: target address high byte
0x7f: CRC8 calculated for the 128B block of data from 0x80-0xff
- this must be written by the user when preparing data for write
operation
- this is update by the MCU after reading the data from flash memory
0x80: 128B block of EEPROM data (either read from code memory or to be
... written)
0xff