keychron_qmk_firmware/keyboards/xd84/dev.md

XD84

Development docs covering the following:

• Kimera core
• RGB
• Backlight
• Light Through Cat

Kimera core

What little available info that was available for the qmk port

• atmega32u4 16Mhz
  • board seems to have a 6Mhz crystal
• 2x PCA9555 I2C IO expander

Links:

• Schematic, BOM, Gerbers
• Original firmware

/*
Kimera_core_v1.0 Components

             U1 (atmega32u4)
           ,----------------.
      TX --| TX0(PD3)   RAW |--
      RX --| RX1(PD2)   GND |--
         --| GND      RESET |-- RST
         --| GND        VCC |--
     SDA --| 2(PD1) (PF4)A3 |--
     SCL --| 3(PD0) (PF5)A2 |--
   (INT) --| 4(PD4) (PF6)A1 |--
         --| 5(PC6) (PF7)A0 |--
         --| 6(PD7) (PB1)15 |-- SCK
    LED2 --| 7(PE6) (PB3)14 |-- MISO
    LED1 --| 8(PB4) (PB2)16 |-- MOSI
    LED3 --| 9(PB5) (PB6)10 |-- LED4
          `----------------'

         IC1 (PCA9555)                  IC2 (PCA9555)
         ,----------.                   ,----------.
   SDA --| SDA  P00 |-- P1        SDA --| SDA  P00 |-- P17
   SCL --| SCL  P01 |-- P2        SCL --| SCL  P01 |-- P18
   INT --| INT  P02 |-- P3        INT --| INT  P02 |-- P19
         |      P03 |-- P4              |      P03 |-- P20
   GND --| A0   P04 |-- P5        VCC --| A0   P04 |-- P21
   SJ1 --| A1   P05 |-- P6        SJ1 --| A1   P05 |-- P22
   SJ2 --| A2   P06 |-- P7        SJ2 --| A2   P06 |-- P23
         |      P07 |-- P8              |      P07 |-- P24
         |          |                   |          |
         |      P10 |-- P9              |      P10 |-- P25
         |      P11 |-- P10             |      P11 |-- P26
         |      P12 |-- P11             |      P12 |-- P27
         |      P13 |-- P12             |      P13 |-- P28
         |      P14 |-- P13             |      P14 |-- P29
         |      P15 |-- P14             |      P15 |-- P30
         |      P16 |-- P15             |      P16 |-- P31
         |      P17 |-- P16             |      P17 |-- P32
         `----------'                   `----------'
*/

Bootloader

Default bootloader is atmel-dfu. Reboot to bootloader via magnetic switch next to icsp header. Flash using regular dfu methods.

XD84 pin mappings

Taken from kimera-config.json

"row_mapping": [ 1, 2, 3, 4, 5, 6 ],
"col_mapping": [ 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31 ],

RGB

• PIN C7
• Number of RGB LED 7

Backlight

• PIN B6

Light Through Cat

TODO - PWM C6

Assumptions

Pin/Port mappings

• All cols are on the same IC
• All rows are on the same IC and port
• Pins mapped sequentially
• Each port only does row or column not a mixture of both
  • No need to have complex port config

ROW index	Kimera Pin	PCA9555
0	1	IC1 Port 0 pin 0
1	2	IC1 Port 0 pin 1
2	3	IC1 Port 0 pin 2
3	4	IC1 Port 0 pin 3
4	5	IC1 Port 0 pin 4
5	6	IC1 Port 0 pin 5

• Safe enough to assume row_index == pin

COL index	Kimera Pin	PCA9555
0	17	IC2 Port 0 pin 0
1	18	IC2 Port 0 pin 1
2	19	IC2 Port 0 pin 2
3	20	IC2 Port 0 pin 3
4	21	IC2 Port 0 pin 4
5	22	IC2 Port 0 pin 5
6	23	IC2 Port 0 pin 6
7	24	IC2 Port 0 pin 7
8	25	IC2 Port 1 pin 0
9	26	IC2 Port 1 pin 1
10	27	IC2 Port 1 pin 2
11	28	IC2 Port 1 pin 3
12	29	IC2 Port 1 pin 4
13	30	IC2 Port 1 pin 5
14	31	IC2 Port 1 pin 6

• Safe enough to assume here col_index does not need to be converted to pin
• Reading both ports one after the other gives us the same sequential behavior
  • maps to the usual practice of reading matrix columns
  • while this technically gives 16 column reads, the 16th column can never be set so is safely ignored

Notes

pca9555 datasheet

• Other Kimera based boards with non sequential pin mappings, pins mapped across ICs, or mixed row/col configs will need more complicated pin -> i2c_addr,port,pin logic as well as rather more complex pin functions.

Return to stock firmware

Not tested but original firmware seems to be available in the kairyu/tkg-firmware repo.