drivers: adc: ltc2451: Add ltc2451 driver

Adds support for the Linear Technologies LTC2451 ADC.

Signed-off-by: Ethan Duckett <ethan.duckett@brillpower.com>

drivers/adc/CMakeLists.txt

@@ -47,3 +47,4 @@ zephyr_library_sources_ifdef(CONFIG_ADC_NXP_S32_ADC_SAR	adc_nxp_s32_adc_sar.c)
 zephyr_library_sources_ifdef(CONFIG_ADC_MAX1125X	adc_max1125x.c)
 zephyr_library_sources_ifdef(CONFIG_ADC_MAX11102_17	adc_max11102_17.c)
 zephyr_library_sources_ifdef(CONFIG_ADC_AD5592	        adc_ad5592.c)
+zephyr_library_sources_ifdef(CONFIG_ADC_LTC2451 adc_ltc2451.c)

drivers/adc/Kconfig

@@ -118,4 +118,6 @@ source "drivers/adc/Kconfig.max11102_17"
 
 source "drivers/adc/Kconfig.ad5592"
 
+source "drivers/adc/Kconfig.ltc2451"
+
 endif # ADC

drivers/adc/Kconfig.ltc2451

@@ -0,0 +1,12 @@
+# Copyright (c) 2023 Brill Power
+# SPDX-License-Identifier: Apache-2.0
+
+config ADC_LTC2451
+	bool "LTC2451 driver"
+	default y
+	depends on DT_HAS_LLTC_LTC2451_ENABLED
+	select I2C
+
+module = ADC_LTC2451
+module-str = ADC_LTC2451
+source "subsys/logging/Kconfig.template.log_config"

drivers/adc/adc_ltc2451.c

@@ -0,0 +1,102 @@
+/* LLTC LTC2451 ADC
+ *
+ * Copyright (c) 2023 Brill Power Ltd.
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/adc.h>
+#include <zephyr/drivers/i2c.h>
+#include <zephyr/logging/log.h>
+
+LOG_MODULE_REGISTER(ltc2451, CONFIG_ADC_LOG_LEVEL);
+
+#define DT_DRV_COMPAT lltc_ltc2451
+
+struct ltc2451_config {
+	struct i2c_dt_spec i2c;
+	uint8_t conversion_speed;
+};
+
+static int ltc2451_channel_setup(const struct device *dev,
+				const struct adc_channel_cfg *channel_cfg)
+{
+	(void)dev;
+	(void)channel_cfg;
+	return 0; /* there is only 1 channel which requires no real setup */
+}
+
+static int ltc2451_set_conversion_speed(const struct device *dev, uint8_t conversion_speed)
+{
+	const struct ltc2451_config *config = dev->config;
+	uint8_t wr_buf[1];
+	int err;
+
+	if (conversion_speed == 60) {
+		wr_buf[0] = 0;
+	} else if (conversion_speed == 30) {
+		wr_buf[0] = 1;
+	} else {
+		LOG_ERR("Invalid conversion speed selected");
+		return -EINVAL;
+	}
+
+	err = i2c_write_dt(&config->i2c, wr_buf, sizeof(wr_buf));
+
+	if (err != 0) {
+		LOG_ERR("LTC write failed (err %d)", err);
+	}
+
+	return err;
+}
+
+static int ltc2451_read_latest_conversion(const struct device *dev,
+					  const struct adc_sequence *sequence)
+{
+	uint8_t rd_buf[2];
+	const struct ltc2451_config *config = dev->config;
+	uint16_t *value_buf;
+
+	int err = i2c_read_dt(&config->i2c, rd_buf, sizeof(rd_buf));
+
+	if (err == 0) {
+		value_buf = (uint16_t *)sequence->buffer;
+		value_buf[0] = (rd_buf[0] << 8) | rd_buf[1];
+	} else {
+		LOG_ERR("LTC read failed (err %d)", err);
+	}
+
+	return err;
+}
+
+static int ltc2451_init(const struct device *dev)
+{
+	const struct ltc2451_config *config = dev->config;
+
+	if (!device_is_ready(config->i2c.bus)) {
+		LOG_ERR("I2C device not ready");
+		return -ENODEV;
+	}
+
+	int err = ltc2451_set_conversion_speed(dev, config->conversion_speed);
+
+	return err;
+}
+
+static const struct adc_driver_api ltc2451_api = {
+	.channel_setup = ltc2451_channel_setup,
+	.read = ltc2451_read_latest_conversion,
+};
+
+#define INIT_LTC2451_DEVICE(index) \
+	static const struct ltc2451_config ltc2451_cfg_##index = { \
+		.i2c = I2C_DT_SPEC_INST_GET(index), \
+		.conversion_speed = DT_INST_PROP(index, conversion_speed), \
+	}; \
+ \
+	DEVICE_DT_INST_DEFINE(index, &ltc2451_init, NULL, NULL, \
+			      &ltc2451_cfg_##index, POST_KERNEL, CONFIG_ADC_INIT_PRIORITY, \
+			      &ltc2451_api);
+
+DT_INST_FOREACH_STATUS_OKAY(INIT_LTC2451_DEVICE)

dts/bindings/adc/lltc,ltc2451.yaml

@@ -0,0 +1,19 @@
+# Copyright (c) 2023 Brill Power Ltd. All Rights Reserved.
+# SPDX-License-Identifier: Apache-2.0
+
+description: Linear Technology LTC2451 ADC
+
+compatible: "lltc,ltc2451"
+
+include: base.yaml
+
+properties:
+  reg:
+    required: true
+
+  conversion-speed:
+    type: int
+    enum:
+      - 30
+      - 60
+    description: Set conversion speed in Hz

tests/drivers/build_all/adc/boards/native_posix.overlay

@@ -87,6 +87,13 @@
 				reg = <0x7>;
 				#io-channel-cells = <1>;
 			};
+
+			test_i2c_ltc2451: ltc2451@8{
+				compatible = "lltc,ltc2451";
+				reg = <0x8>;
+				conversion-speed = <60>;
+				#io-channel-cells = <1>;
+			};
 		};
 
 		test_spi: spi@33334444 {

tests/drivers/build_all/adc/testcase.yaml

@@ -18,6 +18,7 @@ tests:
       - adc_ads114s08
       - adc_emul
       - adc_max1125x
+      - adc_ltc2451
     extra_args: "CONFIG_GPIO=y"
   drivers.adc.cc32xx.build:
     platform_allow: cc3220sf_launchxl