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drivers: sensor: add support for MAX6675
Add support for MAX6675 cold-junction-compensated K-thermocouple to digital converter. Signed-off-by: Gerard Marull-Paretas <[email protected]>
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‎drivers/sensor/CMakeLists.txt‎

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@@ -52,6 +52,7 @@ add_subdirectory_ifdef(CONFIG_LSM9DS0_MFD lsm9ds0_mfd)
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add_subdirectory_ifdef(CONFIG_MAX17055 max17055)
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add_subdirectory_ifdef(CONFIG_MAX30101 max30101)
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add_subdirectory_ifdef(CONFIG_MAX44009 max44009)
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add_subdirectory_ifdef(CONFIG_MAX6675 max6675)
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add_subdirectory_ifdef(CONFIG_MCP9808 mcp9808)
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add_subdirectory_ifdef(CONFIG_MPR mpr)
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add_subdirectory_ifdef(CONFIG_MPU6050 mpu6050)

‎drivers/sensor/Kconfig‎

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@@ -142,6 +142,8 @@ source "drivers/sensor/max30101/Kconfig"
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source "drivers/sensor/max44009/Kconfig"
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source "drivers/sensor/max6675/Kconfig"
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source "drivers/sensor/mchp_tach_xec/Kconfig"
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source "drivers/sensor/mcp9808/Kconfig"

‎drivers/sensor/max6675/CMakeLists.txt‎

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# Copyright (c) 2021 Teslabs Engineering S.L.
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# SPDX-License-Identifier: Apache-2.0
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zephyr_library()
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zephyr_library_sources_ifdef(CONFIG_MAX6675 max6675.c)

‎drivers/sensor/max6675/Kconfig‎

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# Copyright (c) 2021 Teslabs Engineering S.L.
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# SPDX-License-Identifier: Apache-2.0
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config MAX6675
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bool "MAX6675 K-thermocouple to digital converter"
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depends on SPI
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help
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Enable MAX6675 cold-junction-compensated K-thermocouple to digital
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converter.

‎drivers/sensor/max6675/max6675.c‎

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/*
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* Copyright (c) 2021 Teslabs Engineering S.L.
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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 maxim_max6675
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#include <drivers/sensor.h>
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#include <drivers/spi.h>
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#include <sys/byteorder.h>
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#include <logging/log.h>
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LOG_MODULE_REGISTER(max6675, CONFIG_SENSOR_LOG_LEVEL);
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/** Thermocouple input bit (goes high if thermocouple is disconnected). */
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#define THERMOCOUPLE_INPUT BIT(2)
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/** Temperature position. */
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#define TEMPERATURE_POS 3U
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/** Temperature resolution (cDeg/LSB). */
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#define TEMPERATURE_RES 25U
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struct max6675_config {
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const char *spi_label;
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struct spi_config spi_config;
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const char *spi_cs_label;
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gpio_pin_t spi_cs_pin;
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gpio_dt_flags_t spi_cs_flags;
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};
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struct max6675_data {
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const struct device *spi;
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struct spi_cs_control cs_ctrl;
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uint16_t sample;
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};
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static int max6675_sample_fetch(const struct device *dev,
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enum sensor_channel chan)
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{
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struct max6675_data *data = dev->data;
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const struct max6675_config *config = dev->config;
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int ret;
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uint8_t buf_rx[2];
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const struct spi_buf rx_buf = {
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.buf = buf_rx,
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.len = ARRAY_SIZE(buf_rx)
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};
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const struct spi_buf_set rx_bufs = {
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.buffers = &rx_buf,
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.count = 1U
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};
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if (chan != SENSOR_CHAN_ALL && chan != SENSOR_CHAN_AMBIENT_TEMP) {
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return -ENOTSUP;
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}
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ret = spi_read(data->spi, &config->spi_config, &rx_bufs);
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if (ret < 0) {
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return ret;
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}
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data->sample = sys_get_be16(buf_rx);
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if (data->sample & THERMOCOUPLE_INPUT) {
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LOG_INF("Thermocouple not connected");
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return -ENOENT;
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}
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return 0;
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}
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static int max6675_channel_get(const struct device *dev, enum sensor_channel chan,
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struct sensor_value *val)
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{
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struct max6675_data *data = dev->data;
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int32_t temperature;
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if (chan != SENSOR_CHAN_AMBIENT_TEMP) {
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return -ENOTSUP;
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}
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temperature = (data->sample >> TEMPERATURE_POS) * TEMPERATURE_RES;
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val->val1 = temperature / 100;
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val->val2 = (temperature - val->val1 * 100) * 10000;
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return 0;
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}
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static const struct sensor_driver_api max6675_api = {
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.sample_fetch = &max6675_sample_fetch,
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.channel_get = &max6675_channel_get,
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};
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static int max6675_init(const struct device *dev)
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{
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struct max6675_data *data = dev->data;
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const struct max6675_config *config = dev->config;
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data->spi = device_get_binding(config->spi_label);
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if (data->spi == NULL) {
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LOG_ERR("Could not get SPI device %s", config->spi_label);
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return -ENODEV;
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}
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data->cs_ctrl.gpio_dev = device_get_binding(config->spi_cs_label);
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if (data->cs_ctrl.gpio_dev != NULL) {
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data->cs_ctrl.gpio_pin = config->spi_cs_pin;
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data->cs_ctrl.gpio_dt_flags = config->spi_cs_flags;
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data->cs_ctrl.delay = 0U;
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}
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return 0;
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}
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#define MAX6675_INIT(n) \
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static struct max6675_data max6675_data_##n; \
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\
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static const struct max6675_config max6675_config_##n = { \
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.spi_label = DT_INST_BUS_LABEL(n), \
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.spi_config = { \
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.frequency = DT_INST_PROP_OR(n, spi_max_frequency, 0U),\
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.operation = SPI_OP_MODE_MASTER | SPI_WORD_SET(8U), \
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.slave = DT_INST_REG_ADDR(n), \
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.cs = &max6675_data_##n.cs_ctrl, \
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}, \
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.spi_cs_label = UTIL_AND( \
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DT_INST_SPI_DEV_HAS_CS_GPIOS(n), \
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DT_INST_SPI_DEV_CS_GPIOS_LABEL(n)), \
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.spi_cs_pin = UTIL_AND( \
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DT_INST_SPI_DEV_HAS_CS_GPIOS(n), \
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DT_INST_SPI_DEV_CS_GPIOS_PIN(n)), \
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.spi_cs_flags = UTIL_AND( \
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DT_INST_SPI_DEV_HAS_CS_GPIOS(n), \
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DT_INST_SPI_DEV_CS_GPIOS_FLAGS(n)), \
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}; \
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\
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DEVICE_DT_INST_DEFINE(n, &max6675_init, device_pm_control_nop, \
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&max6675_data_##n, &max6675_config_##n, \
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POST_KERNEL, CONFIG_SENSOR_INIT_PRIORITY, \
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&max6675_api);
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DT_INST_FOREACH_STATUS_OKAY(MAX6675_INIT)

‎dts/bindings/sensor/maxim,max6675.yaml‎

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# Copyright (c) 2021, Teslabs Engineering S.L.
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# SPDX-License-Identifier: Apache-2.0
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description: MAX6675 K-thermocouple to digital converter
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compatible: "maxim,max6675"
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include: spi-device.yaml

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