151 lines
3.7 KiB
C
151 lines
3.7 KiB
C
/*
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* Copyright (c) 2021 Laird Connectivity
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#define DT_DRV_COMPAT microchip_mcp4725
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#include <zephyr/kernel.h>
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#include <zephyr/drivers/i2c.h>
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#include <zephyr/drivers/dac.h>
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#include <zephyr/logging/log.h>
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LOG_MODULE_REGISTER(dac_mcp4725, CONFIG_DAC_LOG_LEVEL);
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/* Information in this file comes from MCP4725 datasheet revision D
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* found at https://ww1.microchip.com/downloads/en/DeviceDoc/22039d.pdf
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*/
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/* Defines for field values in MCP4725 DAC register */
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#define MCP4725_DAC_MAX_VAL 0xFFF
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#define MCP4725_FAST_MODE_POWER_DOWN_POS 4U
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#define MCP4725_FAST_MODE_DAC_UPPER_VAL_POS 8U
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#define MCP4725_FAST_MODE_DAC_UPPER_VAL_MASK 0xF
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#define MCP4725_FAST_MODE_DAC_LOWER_VAL_MASK 0xFF
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#define MCP4725_READ_RDY_POS 7U
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#define MCP4725_READ_RDY_MASK (0x1 << MCP4725_READ_RDY_POS)
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/* After writing eeprom, the MCP4725 can be in a busy state for 25 - 50ms
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* See section 1.0 of MCP4725 datasheet, 'Electrical Characteristics'
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*/
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#define MCP4725_BUSY_TIMEOUT_MS 60U
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struct mcp4725_config {
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struct i2c_dt_spec i2c;
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};
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/* Read mcp4725 and check RDY status bit */
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static int mcp4725_wait_until_ready(const struct device *dev)
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{
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const struct mcp4725_config *config = dev->config;
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uint8_t rx_data[5];
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bool mcp4725_ready = false;
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int ret;
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int32_t timeout = k_uptime_get_32() + MCP4725_BUSY_TIMEOUT_MS;
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/* Wait until RDY bit is set or return error if timer exceeds MCP4725_BUSY_TIMEOUT_MS */
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while (!mcp4725_ready) {
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ret = i2c_read_dt(&config->i2c, rx_data, sizeof(rx_data));
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if (ret == 0) {
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mcp4725_ready = rx_data[0] & MCP4725_READ_RDY_MASK;
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} else {
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/* I2C error */
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return ret;
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}
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if (k_uptime_get_32() > timeout) {
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return -ETIMEDOUT;
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}
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}
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return 0;
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}
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/* MCP4725 is a single channel 12 bit DAC */
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static int mcp4725_channel_setup(const struct device *dev,
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const struct dac_channel_cfg *channel_cfg)
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{
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if (channel_cfg->channel_id != 0) {
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return -EINVAL;
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}
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if (channel_cfg->resolution != 12) {
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return -ENOTSUP;
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}
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if (channel_cfg->internal) {
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return -ENOTSUP;
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}
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return 0;
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}
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static int mcp4725_write_value(const struct device *dev, uint8_t channel,
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uint32_t value)
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{
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const struct mcp4725_config *config = dev->config;
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uint8_t tx_data[2];
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int ret;
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if (channel != 0) {
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return -EINVAL;
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}
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/* Check value isn't over 12 bits */
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if (value > MCP4725_DAC_MAX_VAL) {
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return -ENOTSUP;
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}
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/* WRITE_MODE_FAST message format (2 bytes):
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*
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* || 15 14 | 13 12 | 11 10 9 8 || 7 6 5 4 3 2 1 0 ||
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* || Fast mode (0) | Power-down bits (0) | DAC value[11:8] || DAC value[7:0] ||
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*/
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tx_data[0] = ((value >> MCP4725_FAST_MODE_DAC_UPPER_VAL_POS) &
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MCP4725_FAST_MODE_DAC_UPPER_VAL_MASK);
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tx_data[1] = (value & MCP4725_FAST_MODE_DAC_LOWER_VAL_MASK);
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ret = i2c_write_dt(&config->i2c, tx_data, sizeof(tx_data));
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return ret;
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}
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static int dac_mcp4725_init(const struct device *dev)
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{
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const struct mcp4725_config *config = dev->config;
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if (!device_is_ready(config->i2c.bus)) {
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LOG_ERR("I2C device not found");
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return -EINVAL;
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}
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/* Check we can read a 'RDY' bit from this device */
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if (mcp4725_wait_until_ready(dev)) {
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return -EBUSY;
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}
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return 0;
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}
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static const struct dac_driver_api mcp4725_driver_api = {
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.channel_setup = mcp4725_channel_setup,
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.write_value = mcp4725_write_value,
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};
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#define INST_DT_MCP4725(index) \
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static const struct mcp4725_config mcp4725_config_##index = { \
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.i2c = I2C_DT_SPEC_INST_GET(index), \
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}; \
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\
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DEVICE_DT_INST_DEFINE(index, dac_mcp4725_init, \
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NULL, \
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NULL, \
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&mcp4725_config_##index, POST_KERNEL, \
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CONFIG_DAC_MCP4725_INIT_PRIORITY, \
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&mcp4725_driver_api);
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DT_INST_FOREACH_STATUS_OKAY(INST_DT_MCP4725);
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