qmk_firmware/drivers/sensors/pmw3320.c

/* Copyright 2021 Colin Lam (Ploopy Corporation)
 * Copyright 2020 Christopher Courtney, aka Drashna Jael're  (@drashna) <drashna@live.com>
 * Copyright 2019 Sunjun Kim
 * Copyright 2019 Hiroyuki Okada
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#include "pmw3320.h"
#include "wait.h"
#include "debug.h"
#include "gpio.h"

void pmw3320_init(void) {
    // Initialize sensor serial pins.
    gpio_set_pin_output(PMW3320_SCLK_PIN);
    gpio_set_pin_output(PMW3320_SDIO_PIN);
    gpio_set_pin_output(PMW3320_CS_PIN);

    // reboot the sensor.
    pmw3320_write_reg(REG_Power_Up_Reset, 0x5a);

    // wait maximum time before sensor is ready.
    // this ensures that the sensor is actually ready after reset.
    wait_ms(55);

    // read a burst from the sensor and then discard it.
    // gets the sensor ready for write commands
    // (for example, setting the dpi).
    pmw3320_read_burst();

    // Pretty sure that this shouldn't be in the driver.
    // Probably device specific?
    // Set rest mode to default
    pmw3320_write_reg(REG_Rest_Mode_Status, 0x00);
    // Set LED to be always on
    pmw3320_write_reg(REG_Led_Control, 0x4);
    // Disable rest mode
    pmw3320_write_reg(REG_Performance, 0x80);
}

// Perform a synchronization with sensor.
// Just as with the serial protocol, this is used by the slave to send a
// synchronization signal to the master.
void pmw3320_sync(void) {
    gpio_write_pin_low(PMW3320_CS_PIN);
    wait_us(1);
    gpio_write_pin_high(PMW3320_CS_PIN);
}

void pmw3320_cs_select(void) {
    gpio_write_pin_low(PMW3320_CS_PIN);
}

void pmw3320_cs_deselect(void) {
    gpio_write_pin_high(PMW3320_CS_PIN);
}

uint8_t pmw3320_serial_read(void) {
    gpio_set_pin_input(PMW3320_SDIO_PIN);
    uint8_t byte = 0;

    for (uint8_t i = 0; i < 8; ++i) {
        gpio_write_pin_low(PMW3320_SCLK_PIN);
        wait_us(1);

        byte = (byte << 1) | gpio_read_pin(PMW3320_SDIO_PIN);

        gpio_write_pin_high(PMW3320_SCLK_PIN);
        wait_us(1);
    }

    return byte;
}

void pmw3320_serial_write(uint8_t data) {
    gpio_set_pin_output(PMW3320_SDIO_PIN);

    for (int8_t b = 7; b >= 0; b--) {
        gpio_write_pin_low(PMW3320_SCLK_PIN);

        if (data & (1 << b))
            gpio_write_pin_high(PMW3320_SDIO_PIN);
        else
            gpio_write_pin_low(PMW3320_SDIO_PIN);

        wait_us(2);

        gpio_write_pin_high(PMW3320_SCLK_PIN);
    }

    // This was taken from ADNS5050 driver.
    // There's no any info in PMW3320 datasheet about this...
    // tSWR. See page 15 of the ADNS5050 spec sheet.
    // Technically, this is only necessary if the next operation is an SDIO
    // read. This is not guaranteed to be the case, but we're being lazy.
    wait_us(4);

    // Note that tSWW is never necessary. All write operations require at
    // least 32us, which exceeds tSWW, so there's never a need to wait for it.
}

// Read a byte of data from a register on the sensor.
uint8_t pmw3320_read_reg(uint8_t reg_addr) {
    pmw3320_cs_select();

    pmw3320_serial_write(reg_addr);

    uint8_t byte = pmw3320_serial_read();

    // This was taken directly from ADNS5050 driver...
    // tSRW & tSRR. See page 15 of the ADNS5050 spec sheet.
    // Technically, this is only necessary if the next operation is an SDIO
    // read or write. This is not guaranteed to be the case.
    // Honestly, this wait could probably be removed.
    wait_us(1);

    pmw3320_cs_deselect();

    return byte;
}

void pmw3320_write_reg(uint8_t reg_addr, uint8_t data) {
    pmw3320_cs_select();
    pmw3320_serial_write(0b10000000 | reg_addr);
    pmw3320_serial_write(data);
    pmw3320_cs_deselect();
}

report_pmw3320_t pmw3320_read_burst(void) {
    pmw3320_cs_select();

    report_pmw3320_t data;
    data.dx = 0;
    data.dy = 0;

    pmw3320_serial_write(REG_Motion_Burst);

    uint8_t x = pmw3320_serial_read();
    uint8_t y = pmw3320_serial_read();

    // Probably burst mode may include contents of delta_xy register,
    // which contain HI parts of x/y deltas, but I had no luck finding it.
    // Probably it's required to activate 12-bit mode to access this data.
    // So we end burst mode early to not read unneeded information.
    pmw3320_cs_deselect();

    data.dx = convert_twoscomp(x);
    data.dy = convert_twoscomp(y);

    return data;
}

// Convert a two's complement byte from an unsigned data type into a signed
// data type.
int8_t convert_twoscomp(uint8_t data) {
    if ((data & 0x80) == 0x80)
        return -128 + (data & 0x7F);
    else
        return data;
}

uint16_t pmw3320_get_cpi(void) {
    uint8_t cpival = pmw3320_read_reg(REG_Resolution);
    // 0x1F is an inversion of 0x20 which is 0b100000
    return (uint16_t)((cpival & 0x1F) * PMW3320_CPI_STEP);
}

void pmw3320_set_cpi(uint16_t cpi) {
    uint8_t cpival = constrain((cpi / PMW3320_CPI_STEP), (PMW3320_CPI_MIN / PMW3320_CPI_STEP), (PMW3320_CPI_MAX / PMW3320_CPI_STEP)) - 1U;
    // Fifth bit is probably a control bit.
    // PMW3320 datasheet don't have any info on this, so this is a pure guess.
    pmw3320_write_reg(REG_Resolution, 0x20 | cpival);
}

bool pmw3320_check_signature(void) {
    uint8_t pid  = pmw3320_read_reg(REG_Product_ID);
    uint8_t pid2 = pmw3320_read_reg(REG_Inverse_Product_ID);

    return (pid == 0x3b && pid2 == 0xc4);
}