qmk_firmware/keyboards/handwired/symmetric70_proto/matrix_fast/readme.md

Fast and extensible matrix.c

This matrix.c is faster and more extensible than the standard quantum/matrix.c.

• The execution speed of the matrix_scan() function is several times faster than quantum/matrix.c.
• In addition to handling MCU GPIOs, it can be extended to handle I/O extenders.

ToDo list

• support Pro Micro
• support Proton-C
• support DIRECT_PINS
• support DIODE_DIRECTION == ROW2COL
• support 74HC157: quadruple 2-line to 1-line data selectors / multiplexers
• support 74HC153: dual 4-line to 1-line data selectors / multiplexers
• support I/O expander (MCP23018)
• support MCU & I/O expander (MCP23018) mixture like ErgoDox

Current performance

MCU	delay type	execution time of matrix_scan()	matrix scan rate
Pro Micro (16MHz)	fast adaptive	75.6us	8090 scans/sec
Proton C (72MHz)	fast adaptive	49.8us	15100 scans/sec

Configuration

This matrix.c requires a different configuration than quantum/matrix.c.

Output pins configuration

The output pins is the Row pins if DIODE_DIRECTION == COL2ROW, and the Col pins if DIODE_DIRECTION == ROW2COL. When DIRECT_PINS is defined, the output pins do not need to be set.

Example:

// list of OUTPUT(row) ports
#define MATRIX_OUT_PORTS  \
    (Port_D, MCU_GPIO, D0), \
    (Port_C, MCU_GPIO, C0), \
    (Port_E, MCU_GPIO, E0), \
    (Port_B, MCU_GPIO, B0)
// list of OUTPUT pins
#define MATRIX_OUT_PINS  \
    (0, Port_D, 4), \
    (1, Port_C, 6), \
    (2, Port_D, 7), \
    (3, Port_E, 6), \
    (4, Port_B, 4), \
    (5, Port_B, 5)

Input pins configuration

The input pins is the Col pins if DIODE_DIRECTION == COL2ROW, and the Row pins if DIODE_DIRECTION == ROW2COL. When DIRECT_PINS is defined, the input pin settings will enumerate the connection pins of all switches.

Example:

// list of INPUT ports
#define MATRIX_IN_PORTS (Port_F, MCU_GPIO, F0), (Port_B, MCU_GPIO, B0)
// list of INPUT pins
#define MATRIX_IN_PINS \
    (0, Port_F, 4), \
    (1, Port_F, 5), \
    (2, Port_F, 6), \
    (3, Port_F, 7), \
    (4, Port_B, 1), \
    (5, Port_B, 3)

Multiplexer Extension

By defining the MATRIX_EXTENSION_74HC157 macro or MATRIX_EXTENSION_74HC153 macro, you can connect a multiplexer to the GPIO to extend the input pins.

Example:

#define MATRIX_EXTENSION_74HC157 B2 /* or #define MATRIX_EXTENSION_74HC153 B2, B6 */

// list of OUTPUT ports
#define MATRIX_OUT_PORTS (Port_D, MCU_GPIO, D0), (Port_C, MCU_GPIO, C0), (Port_E, MCU_GPIO, E0), (Port_B, MCU_GPIO, B0)
// list of OUTPUT pins
#define MATRIX_OUT_PINS  (0, Port_D, 4), (1, Port_C, 6), (2, Port_D, 7), (3, Port_E, 6), (4, Port_B, 4), (5, Port_B, 5)

// list of INPUT ports
#define MATRIX_IN_PORTS \
    (Port_Fa, MCU_GPIOa, F0), \
    (Port_Ba, MCU_GPIOa, B0), \
    (Port_Fb, MCU_GPIOb, F0), \
    (Port_Bb, MCU_GPIOb, B0)
// list of INPUT pins
#define MATRIX_IN_PINS \
    (0, Port_Fa, 4), \
    (1, Port_Fb, 5), \
    (2, Port_Fb, 6), \
    (3, Port_Fa, 7), \
    (4, Port_Ba, 1), \
    (5, Port_Bb, 3)

I/O expander Extension

I plan to provide extensions to support I/O expanders such as MCP23018 and PCA9555.

Compile

• Measure the execution time of matrix_scan()
  • make MTEST=matrix_debug_scan[,<other options>..] handwired/symmetric70_proto/promicro/fast:default:flash
• Measure delay time.
  • make MTEST=matrix_debug_delay[,<other options>..] handwired/symmetric70_proto/promicro/fast:default:flash

Measurement result

Pro Micro (ATmega32u4 16Mhz)

Default setting (show matrix_scan() time)

• make MTEST=matrix_debug_scan handwired/symmetric70_proto/promicro/fast:default:flash
• CH1: Row 0
• CH2: Row 1
• CH3: Row 4
• CH4: matrix_scan()
• Execution time of matrix_scan() 75.6us
• Frequency of matrix scan 8.09kHz (123.6us)

Default setting (show delay time)

• make MTEST=matrix_debug_delay handwired/symmetric70_proto/promicro/fast:default:flash

Press R0C0 key

• CH1: Row 0
• CH2: Row 1
• CH3: Row 4
• CH4: delay time
• Frequency of matrix scan 7.84kHz (127.6us)

Proton C

Default setting (show matrix_scan() time)

• make MTEST=matrix_debug_scan handwired/symmetric70_proto/proton_c/fast:default:flash
• CH1: Row 0
• CH2: Row 1
• CH3: Row 4
• CH4: matrix_scan()
• Execution time of matrix_scan() 49.8us
• Frequency of matrix scan 15.1kHz (66.2.6us)

Default setting (show delay time)

• make MTEST=matrix_debug_delay handwired/symmetric70_proto/proton_c/fast:default:flash

Press R0C0 key

• CH1: Row 0
• CH2: Row 1
• CH3: Row 4
• CH4: delay time
• Frequency of matrix scan 13.9kHz (71.8us)

Connect a 500pF capacitor between C0 line and GND, Press R0C0, R1C0, R2C0, R3C0, R4C0 keys

• CH1: Row 0
• CH2: Row 1
• CH3: Col 0
• CH4: delay time
• Delay time 11.6us
• Threshold Voltage 1.9V

Connect a 1000pF capacitor between C0 line and GND, Press R0C0, R1C0, R2C0, R3C0, R4C0 keys

• CH1: Row 0
• CH2: Row 1
• CH3: Col 0
• CH4: delay time
• Delay time 18.6us
• Threshold Voltage 1.9V