tactility/Drivers/xpt2046-softspi-module/source/xpt2046_softspi.cpp

// SPDX-License-Identifier: Apache-2.0
#include <drivers/xpt2046_softspi.h>
#include <xpt2046_softspi_module.h>

#include <tactility/check.h>
#include <tactility/device.h>
#include <tactility/driver.h>
#include <tactility/drivers/gpio_controller.h>
#include <tactility/drivers/pointer.h>
#include <tactility/drivers/power_supply.h>
#include <tactility/delay.h>
#include <tactility/error.h>
#include <tactility/log.h>

#include <cstdlib>
#include <new>

#define TAG "XPT2046SoftSPI"
#define GET_CONFIG(device) (static_cast<const Xpt2046SoftSpiConfig*>((device)->config))

// Rough LiPo discharge curve floor, used together with the configured reference voltage
// (the 100% point) to estimate a charge percentage from the sensed v-bat voltage.
#define POWER_SUPPLY_MIN_MV 3200

namespace {

constexpr uint8_t CMD_READ_X = 0xD0;
constexpr uint8_t CMD_READ_Y = 0x90;
// BATTERY register (start=1, addr=010, 12-bit mode, single-ended, PD1=0/PD0=1 i.e. IRQ disabled
// between conversions), same encoding as the hardware-SPI XPT2046 driver's default mode.
constexpr uint8_t CMD_READ_BATTERY = 0xA7;

constexpr int RAW_MIN_DEFAULT = 100;
constexpr int RAW_MAX_DEFAULT = 1900;
constexpr int RAW_VALID_MIN = 100;
constexpr int RAW_VALID_MAX = 3900;
constexpr int SAMPLE_COUNT = 8;

} // namespace

struct Xpt2046SoftSpiInternal {
    GpioDescriptor* mosi;
    GpioDescriptor* miso;
    GpioDescriptor* sck;
    GpioDescriptor* cs;
    bool swap_xy;
    bool mirror_x;
    bool mirror_y;
    bool touched;
    uint16_t x;
    uint16_t y;
    Device* power_supply_device;
};

static error_t create_power_supply_child(Device* parent, Device*& out_child);
static void destroy_power_supply_child(Device* child);

// region Driver lifecycle

static void release_descriptors(Xpt2046SoftSpiInternal* internal) {
    if (internal->mosi != nullptr) gpio_descriptor_release(internal->mosi);
    if (internal->miso != nullptr) gpio_descriptor_release(internal->miso);
    if (internal->sck != nullptr) gpio_descriptor_release(internal->sck);
    if (internal->cs != nullptr) gpio_descriptor_release(internal->cs);
}

static error_t start(Device* device) {
    const auto* config = GET_CONFIG(device);

    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(malloc(sizeof(Xpt2046SoftSpiInternal)));
    if (internal == nullptr) {
        return ERROR_OUT_OF_MEMORY;
    }
    *internal = {};

    internal->mosi = gpio_descriptor_acquire(config->pin_mosi.gpio_controller, config->pin_mosi.pin, GPIO_OWNER_GPIO);
    internal->miso = gpio_descriptor_acquire(config->pin_miso.gpio_controller, config->pin_miso.pin, GPIO_OWNER_GPIO);
    internal->sck = gpio_descriptor_acquire(config->pin_sck.gpio_controller, config->pin_sck.pin, GPIO_OWNER_GPIO);
    internal->cs = gpio_descriptor_acquire(config->pin_cs.gpio_controller, config->pin_cs.pin, GPIO_OWNER_GPIO);

    if (internal->mosi == nullptr || internal->miso == nullptr || internal->sck == nullptr || internal->cs == nullptr) {
        LOG_E(TAG, "Failed to acquire GPIO descriptors");
        release_descriptors(internal);
        free(internal);
        return ERROR_RESOURCE;
    }

    bool ok =
        gpio_descriptor_set_flags(internal->mosi, GPIO_FLAG_DIRECTION_OUTPUT) == ERROR_NONE &&
        gpio_descriptor_set_flags(internal->sck, GPIO_FLAG_DIRECTION_OUTPUT) == ERROR_NONE &&
        gpio_descriptor_set_flags(internal->cs, GPIO_FLAG_DIRECTION_OUTPUT) == ERROR_NONE &&
        gpio_descriptor_set_flags(internal->miso, GPIO_FLAG_DIRECTION_INPUT | GPIO_FLAG_PULL_UP) == ERROR_NONE;

    // Idle state: CS high (deselected), SCK/MOSI low.
    ok = ok &&
        gpio_descriptor_set_level(internal->cs, true) == ERROR_NONE &&
        gpio_descriptor_set_level(internal->sck, false) == ERROR_NONE &&
        gpio_descriptor_set_level(internal->mosi, false) == ERROR_NONE;

    if (!ok) {
        LOG_E(TAG, "Failed to configure GPIO pins");
        release_descriptors(internal);
        free(internal);
        return ERROR_RESOURCE;
    }

    internal->swap_xy = config->swap_xy;
    internal->mirror_x = config->mirror_x;
    internal->mirror_y = config->mirror_y;

    device_set_driver_data(device, internal);

    if (config->power_supply) {
        error_t error = create_power_supply_child(device, internal->power_supply_device);
        if (error != ERROR_NONE) {
            LOG_E(TAG, "Failed to create power-supply device");
            release_descriptors(internal);
            free(internal);
            return error;
        }
    }

    return ERROR_NONE;
}

static error_t stop(Device* device) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));

    if (internal->power_supply_device != nullptr) {
        destroy_power_supply_child(internal->power_supply_device);
    }

    release_descriptors(internal);
    free(internal);
    return ERROR_NONE;
}

// endregion

// region Bit-banged SPI

// XPT2046 protocol: 8-bit command out, 12-bit conversion result back (MSB first), clocked
// manually since no hardware SPI peripheral is available for this pin set (see the binding's
// description). 1us clock half-period is well within the XPT2046's timing budget (it's rated
// for a multi-MHz SPI clock; this bit-bang loop runs orders of magnitude slower).
static int read_spi_command(Xpt2046SoftSpiInternal* internal, uint8_t command) {
    int result = 0;

    gpio_descriptor_set_level(internal->cs, false);
    delay_micros(1);

    for (int i = 7; i >= 0; i--) {
        gpio_descriptor_set_level(internal->mosi, (command & (1 << i)) != 0);
        gpio_descriptor_set_level(internal->sck, true);
        delay_micros(1);
        gpio_descriptor_set_level(internal->sck, false);
        delay_micros(1);
    }

    for (int i = 11; i >= 0; i--) {
        gpio_descriptor_set_level(internal->sck, true);
        delay_micros(1);
        bool level = false;
        gpio_descriptor_get_level(internal->miso, &level);
        if (level) {
            result |= (1 << i);
        }
        gpio_descriptor_set_level(internal->sck, false);
        delay_micros(1);
    }

    gpio_descriptor_set_level(internal->cs, true);

    return result;
}

// endregion

// region Power supply

// The v-bat reading is noisy (bit-banged SPI, no dedicated sample/hold), so it's smoothed by
// averaging over several samples rather than trusting a single conversion.
#define POWER_SUPPLY_SAMPLE_COUNT 20

// Same scaling as the hardware-SPI XPT2046 driver's esp_lcd_touch_xpt2046_read_battery_level():
// the chip halves the v-bat voltage internally, and the raw code is relative to its internal
// 2.507V reference over 12 bits.
static int read_battery_mv(Xpt2046SoftSpiInternal* internal) {
    int64_t raw_sum = 0;
    for (int i = 0; i < POWER_SUPPLY_SAMPLE_COUNT; i++) {
        raw_sum += read_spi_command(internal, CMD_READ_BATTERY);
    }

    int64_t raw_avg = raw_sum / POWER_SUPPLY_SAMPLE_COUNT;
    return (int)((raw_avg * 4 * 2507) / 4096);
}

static bool ps_supports_property(Device*, PowerSupplyProperty property) {
    return property == POWER_SUPPLY_PROP_VOLTAGE || property == POWER_SUPPLY_PROP_CAPACITY;
}

static int estimate_capacity_from_mv(int battery_mv, uint32_t reference_mv) {
    if (battery_mv <= POWER_SUPPLY_MIN_MV) return 0;
    if ((uint32_t)battery_mv >= reference_mv) return 100;
    return (battery_mv - POWER_SUPPLY_MIN_MV) * 100 / ((int)reference_mv - POWER_SUPPLY_MIN_MV);
}

static error_t ps_get_property(Device* device, PowerSupplyProperty property, PowerSupplyPropertyValue* out_value) {
    if (property != POWER_SUPPLY_PROP_VOLTAGE && property != POWER_SUPPLY_PROP_CAPACITY) {
        return ERROR_NOT_SUPPORTED;
    }

    auto* parent = device_get_parent(device);
    const auto* parent_config = GET_CONFIG(parent);
    auto* parent_internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(parent));

    int battery_mv = read_battery_mv(parent_internal);
    out_value->int_value = (property == POWER_SUPPLY_PROP_VOLTAGE) ? battery_mv : estimate_capacity_from_mv(battery_mv, parent_config->power_supply_reference_voltage_mv);
    return ERROR_NONE;
}

static bool ps_supports_charge_control(Device*) { return false; }
static bool ps_is_allowed_to_charge(Device*) { return false; }
static error_t ps_set_allowed_to_charge(Device*, bool) { return ERROR_NOT_SUPPORTED; }
static bool ps_supports_quick_charge(Device*) { return false; }
static bool ps_is_quick_charge_enabled(Device*) { return false; }
static error_t ps_set_quick_charge_enabled(Device*, bool) { return ERROR_NOT_SUPPORTED; }
static bool ps_supports_power_off(Device*) { return false; }
static error_t ps_power_off(Device*) { return ERROR_NOT_SUPPORTED; }

static constexpr PowerSupplyApi XPT2046_SOFTSPI_POWER_SUPPLY_API = {
    .supports_property = ps_supports_property,
    .get_property = ps_get_property,
    .supports_charge_control = ps_supports_charge_control,
    .is_allowed_to_charge = ps_is_allowed_to_charge,
    .set_allowed_to_charge = ps_set_allowed_to_charge,
    .supports_quick_charge = ps_supports_quick_charge,
    .is_quick_charge_enabled = ps_is_quick_charge_enabled,
    .set_quick_charge_enabled = ps_set_quick_charge_enabled,
    .supports_power_off = ps_supports_power_off,
    .power_off = ps_power_off,
};

// Registered (driver_construct_add() in module.cpp) so driver_bind() has a valid ->internal,
// but never matched against a devicetree node: xpt2046_softspi wires it up directly by pointer.
Driver xpt2046_softspi_power_supply_driver = {
    .name = "xpt2046-softspi-power-supply",
    .compatible = (const char*[]) { "xpt2046-softspi-power-supply", nullptr },
    .start_device = nullptr,
    .stop_device = nullptr,
    .api = &XPT2046_SOFTSPI_POWER_SUPPLY_API,
    .device_type = &POWER_SUPPLY_TYPE,
    .owner = &xpt2046_softspi_module,
    .internal = nullptr
};

static error_t create_power_supply_child(Device* parent, Device*& out_child) {
    auto* child = new(std::nothrow) Device { .address = 0, .name = "xpt2046-softspi-power-supply", .config = nullptr, .parent = nullptr, .internal = nullptr };
    if (child == nullptr) {
        return ERROR_OUT_OF_MEMORY;
    }

    error_t error = device_construct(child);
    if (error != ERROR_NONE) {
        delete child;
        return error;
    }

    device_set_parent(child, parent);
    device_set_driver(child, &xpt2046_softspi_power_supply_driver);

    error = device_add(child);
    if (error != ERROR_NONE) {
        device_destruct(child);
        delete child;
        return error;
    }

    error = device_start(child);
    if (error != ERROR_NONE) {
        device_remove(child);
        device_destruct(child);
        delete child;
        return error;
    }

    out_child = child;
    return ERROR_NONE;
}

static void destroy_power_supply_child(Device* child) {
    check(device_stop(child) == ERROR_NONE);
    check(device_remove(child) == ERROR_NONE);
    check(device_destruct(child) == ERROR_NONE);
    delete child;
}

// endregion

// region PointerApi

static error_t xpt2046_softspi_enter_sleep(Device*) {
    // No software-controlled power-down for this bit-banged variant; nothing to do.
    return ERROR_NONE;
}

static error_t xpt2046_softspi_exit_sleep(Device*) {
    return ERROR_NONE;
}

// Takes and averages several raw samples (rejecting out-of-range noise) then maps them onto
// [0, x_max]/[0, y_max], applying swap/mirror. Mirrors the deprecated HAL's Xpt2046SoftSpi driver.
static error_t xpt2046_softspi_read_data(Device* device, TickType_t timeout) {
    (void)timeout;
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    const auto* config = GET_CONFIG(device);

    int total_x = 0;
    int total_y = 0;
    int valid_samples = 0;

    for (int i = 0; i < SAMPLE_COUNT; i++) {
        const int raw_x = read_spi_command(internal, CMD_READ_X);
        const int raw_y = read_spi_command(internal, CMD_READ_Y);

        if (raw_x > RAW_VALID_MIN && raw_x < RAW_VALID_MAX && raw_y > RAW_VALID_MIN && raw_y < RAW_VALID_MAX) {
            total_x += raw_x;
            total_y += raw_y;
            valid_samples++;
        }

        delay_millis(1);
    }

    if (valid_samples < 3) {
        internal->touched = false;
        return ERROR_NONE;
    }

    const int raw_x = total_x / valid_samples;
    const int raw_y = total_y / valid_samples;

    int mapped_x = (raw_x - RAW_MIN_DEFAULT) * static_cast<int>(config->x_max) / (RAW_MAX_DEFAULT - RAW_MIN_DEFAULT);
    int mapped_y = (raw_y - RAW_MIN_DEFAULT) * static_cast<int>(config->y_max) / (RAW_MAX_DEFAULT - RAW_MIN_DEFAULT);

    if (internal->swap_xy) {
        const int swapped = mapped_x;
        mapped_x = mapped_y;
        mapped_y = swapped;
    }
    if (internal->mirror_x) {
        mapped_x = static_cast<int>(config->x_max) - mapped_x;
    }
    if (internal->mirror_y) {
        mapped_y = static_cast<int>(config->y_max) - mapped_y;
    }

    if (mapped_x < 0) mapped_x = 0;
    if (mapped_x > static_cast<int>(config->x_max)) mapped_x = static_cast<int>(config->x_max);
    if (mapped_y < 0) mapped_y = 0;
    if (mapped_y > static_cast<int>(config->y_max)) mapped_y = static_cast<int>(config->y_max);

    internal->x = static_cast<uint16_t>(mapped_x);
    internal->y = static_cast<uint16_t>(mapped_y);
    internal->touched = true;
    return ERROR_NONE;
}

static bool xpt2046_softspi_get_touched_points(Device* device, uint16_t* x, uint16_t* y, uint16_t* strength, uint8_t* point_count, uint8_t max_point_count) {
    (void)strength;
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));

    if (!internal->touched || max_point_count < 1) {
        *point_count = 0;
        return false;
    }

    *x = internal->x;
    *y = internal->y;
    *point_count = 1;
    return true;
}

static error_t xpt2046_softspi_set_swap_xy(Device* device, bool swap) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    internal->swap_xy = swap;
    return ERROR_NONE;
}

static error_t xpt2046_softspi_get_swap_xy(Device* device, bool* swap) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    *swap = internal->swap_xy;
    return ERROR_NONE;
}

static error_t xpt2046_softspi_set_mirror_x(Device* device, bool mirror) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    internal->mirror_x = mirror;
    return ERROR_NONE;
}

static error_t xpt2046_softspi_get_mirror_x(Device* device, bool* mirror) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    *mirror = internal->mirror_x;
    return ERROR_NONE;
}

static error_t xpt2046_softspi_set_mirror_y(Device* device, bool mirror) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    internal->mirror_y = mirror;
    return ERROR_NONE;
}

static error_t xpt2046_softspi_get_mirror_y(Device* device, bool* mirror) {
    auto* internal = static_cast<Xpt2046SoftSpiInternal*>(device_get_driver_data(device));
    *mirror = internal->mirror_y;
    return ERROR_NONE;
}

// endregion

static const PointerApi xpt2046_softspi_pointer_api = {
    .enter_sleep = xpt2046_softspi_enter_sleep,
    .exit_sleep = xpt2046_softspi_exit_sleep,
    .read_data = xpt2046_softspi_read_data,
    .get_touched_points = xpt2046_softspi_get_touched_points,
    .set_swap_xy = xpt2046_softspi_set_swap_xy,
    .get_swap_xy = xpt2046_softspi_get_swap_xy,
    .set_mirror_x = xpt2046_softspi_set_mirror_x,
    .get_mirror_x = xpt2046_softspi_get_mirror_x,
    .set_mirror_y = xpt2046_softspi_set_mirror_y,
    .get_mirror_y = xpt2046_softspi_get_mirror_y,
};

Driver xpt2046_softspi_driver = {
    .name = "xpt2046_softspi",
    .compatible = (const char*[]) { "xptek,xpt2046-softspi", nullptr },
    .start_device = start,
    .stop_device = stop,
    .api = &xpt2046_softspi_pointer_api,
    .device_type = &POINTER_TYPE,
    .owner = &xpt2046_softspi_module,
    .internal = nullptr
};