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Ardupilot
GitHub Repository: Ardupilot/ardupilot
 Path: blob/master/libraries/AP_DAC/AP_DAC_MCP40D1x.cpp
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/*

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  DAC backend for MCP40D1x I2C DACs

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 */

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#include "AP_DAC_config.h"

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#if AP_DAC_MCP40D1X_ENABLED

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#include "AP_DAC.h"

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#include "AP_DAC_MCP40D1x.h"

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#include <AP_HAL/utility/sparse-endian.h>

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#include <GCS_MAVLink/GCS.h>

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#include <AP_HAL/I2CDevice.h>

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// common registers

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#define MCP40D1x_ADDR 0x2E

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#define REG_MCP40D1x_NOP 0x00

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#define REG_MCP40D1x_WIPER_DEFAULT 0x3F

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#ifndef AP_DAC_MCP40D1X_CONVERSION_EQ

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#define AP_DAC_MCP40D1X_CONVERSION_EQ(vo,vr) (vo * 127 / vr)

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#endif

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extern const AP_HAL::HAL &hal;

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void AP_DAC_MCP40D1x::init(void)

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{

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    if (params.bus_address <= 0) {

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        GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "MCP40D1x must be >0");

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        return;

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    }

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    if (!dev) {

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        dev = hal.i2c_mgr->get_device_ptr(params.bus, params.bus_address, 100000, true, 20);

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    }

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    if (!dev) {

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        GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "MCP40D1x device is null at %u:%", unsigned(params.bus), unsigned(params.bus_address));

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        return;

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    }

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    WITH_SEMAPHORE(dev->get_semaphore());

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    dev->set_speed(AP_HAL::Device::SPEED_HIGH);

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    uint8_t wiper_default = 0;

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    if (!dev->read_registers(REG_MCP40D1x_NOP, &wiper_default, 1)) {

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        GCS_SEND_TEXT(MAV_SEVERITY_WARNING, "MCP40D1x not found at %u:%x", unsigned(params.bus), unsigned(params.bus_address));

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        delete dev;

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        return;

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    }

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    initialized = true;

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}

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void AP_DAC_MCP40D1x::update(void)

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{

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    set_voltage(0, params.voltage);

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}

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// set voltage for a channel

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bool AP_DAC_MCP40D1x::set_voltage(uint8_t chan, float v)

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{

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    if (!initialized) {

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        GCS_SEND_TEXT(MAV_SEVERITY_INFO, "MCP40D1x not initialized");

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        return false;

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    }

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    // convert voltage to 7-bit value

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    uint8_t wiper = uint8_t(roundf(AP_DAC_MCP40D1X_CONVERSION_EQ(v, params.voltage_reference)));

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    if (wiper > 127) {

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        wiper = 127;

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    }

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    // Currently only suitable for AP_Periph as called from the main thread

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    WITH_SEMAPHORE(dev->get_semaphore());

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    // write to data register first

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    if (!dev->write_register(REG_MCP40D1x_NOP, wiper, true)) {

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        GCS_SEND_TEXT(MAV_SEVERITY_INFO, "MCP40D1x wiper write fail: %x", unsigned(wiper));

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        return false;

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    }

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    return true;

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}

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#endif // AP_DAC_MCP40D1X_ENABLED

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