samples: sensor: fdc2x1x: Add FDC2X1X sample application

This sample application periodically reads raw data from the FDC2X1X
sensor in polling mode or optionally with data ready trigger.
It is able to read the 12-Bit and 28-Bit, as well as the 2-Channel
and 4-Channel versions (FDC2112, FDC2114, FDC2212, FDC2214).
The 4-channel versions are chosen through devicetree properties.
The default is FDC2112.

Signed-off-by: Igor Knippenberg <igor.knippenberg@gmail.com>

samples/sensor/fdc2x1x/CMakeLists.txt

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+#
+#  Copyright (c) 2020 arithmetics.io
+#
+#  SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.13.1)
+find_package(Zephyr HINTS $ENV{ZEPHYR_BASE})
+project(fdc2x1x)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/sensor/fdc2x1x/README.rst

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+.. _fdc2x1x:
+
+FDC2X1X: Capacitance-to-Digital Converter
+#########################################
+
+Overview
+********
+
+This sample application periodically reads frequency and capacitance data from the
+FDC2X1X sensor in polling mode or optionally with data ready trigger. It is able
+to read the 12-Bit and 28-Bit, as well as the 2-Channel and 4-Channel versions
+(FDC2112, FDC2114, FDC2212, FDC2214). The 4-channel versions are chosen through
+devicetree properties. The default in this sample is the 2-channel version.
+
+Capacitive sensing is a low-power, low-cost, high-resolution contactless sensing
+technique that can be applied to a variety of applications ranging from proximity
+detection and gesture recognition to remote liquid level sensing. The sensor in
+a capacitive sensing system is any metal or conductor, allowing for low cost and
+highly flexible system design.
+The main challenge limiting sensitivity in capacitive sensing applications is
+noise susceptibility of the sensors. With the FDC2x1x innovative EMI resistant
+architecture, performance can be maintained even in presence of high-noise environments.
+
+
+Wiring
+*******
+
+This sample uses the FDC2X1X sensor controlled using the I2C interface.
+Connect supply **VDD** and **GND**. The supply voltage can be in
+the 2.7V to 3.6V range.
+
+Connect **SD** to a GPIO to control the Shutdown Mode.
+
+Connect Interface: **SDA**, **SCL** and optionally connect **INTB** to a
+interrupt capable GPIO.
+
+For detailed description refer to the `FDC2X1X datasheet`_
+at pages 4-5.
+
+
+Building and Running
+********************
+
+This sample outputs sensor data to the console and can be read by any serial
+console program. It should work with any platform featuring a I2C interface.
+The platform in use requires a custom devicetree overlay.
+In this example the :ref:`nrf9160dk_nrf9160` board is used. The devicetree
+overlay of this board provides example settings for evaluation, which
+you can use as a reference for other platforms.
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/sensor/fdc2x1x
+   :board: nrf9160dk_nrf9160
+   :goals: build flash
+   :compact:
+
+Sample Output: 2-Channel, 28-Bit (FDC2212)
+==========================================
+
+.. code-block:: console
+
+        ch0: 5.318888 MHz ch1: 5.150293 MHz
+        ch0: 49.742308 pF ch1: 53.052260 pF
+
+        ch0: 5.318819 MHz ch1: 5.150307 MHz
+        ch0: 49.743612 pF ch1: 53.051964 pF
+
+        ch0: 5.318822 MHz ch1: 5.150200 MHz
+        ch0: 49.743548 pF ch1: 53.054176 pF
+
+        ch0: 5.318752 MHz ch1: 5.150265 MHz
+        ch0: 49.744860 pF ch1: 53.052828 pF
+
+        <repeats endlessly>
+
+
+Sample Output: 4-Channel, 12-Bit (FDC2114)
+==========================================
+
+.. code-block:: console
+
+        ch0: 4.966171 MHz ch1: 4.946465 MHz ch2: 4.985879 MHz ch3: 4.907051 MHz
+        ch0: 57.059016 pF ch1: 57.514568 pF ch2: 56.608844 pF ch3: 58.442204 pF
+
+        ch0: 4.966171 MHz ch1: 4.946465 MHz ch2: 4.985879 MHz ch3: 4.907051 MHz
+        ch0: 57.059016 pF ch1: 57.514568 pF ch2: 56.608844 pF ch3: 58.442204 pF
+
+        ch0: 4.966171 MHz ch1: 4.946465 MHz ch2: 4.985879 MHz ch3: 4.907051 MHz
+        ch0: 57.059016 pF ch1: 57.514568 pF ch2: 56.608844 pF ch3: 58.442204 pF
+
+        ch0: 4.966171 MHz ch1: 4.946465 MHz ch2: 4.985879 MHz ch3: 4.907051 MHz
+        ch0: 57.059016 pF ch1: 57.514568 pF ch2: 56.608844 pF ch3: 58.442204 pF
+
+        <repeats endlessly>
+
+
+References
+**********
+
+FDC2X1X Datasheet and Product Info:
+ https://www.ti.com/product/FDC2114
+
+.. _FDC2X1X datasheet: https://www.ti.com/lit/gpn/fdc2114

samples/sensor/fdc2x1x/boards/nrf9160dk_nrf9160.overlay

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+/*
+ * Copyright (c) 2020 arithmetics.io
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+&i2c2 {
+	clock-frequency = <I2C_BITRATE_FAST>;
+	fdc2x1x@2A {
+		compatible = "ti,fdc2x1x";
+		reg = <0x2A>;
+		label = "FDC2X1X";
+		sd-gpios = <&gpio0 16 GPIO_ACTIVE_HIGH>;
+		intb-gpios = <&gpio0 20 GPIO_ACTIVE_LOW>;
+
+		autoscan;
+		deglitch = <5>;
+		fref = <43360>;
+
+		channel_0 {
+			rcount = <7499>;
+			settlecount = <48>;
+			fref-divider = <1>;
+			idrive = <10>;
+			fin-sel = <2>;
+			inductance = < 18 >;
+		};
+
+		channel_1 {
+			rcount = <7499>;
+			settlecount = <48>;
+			fref-divider = <1>;
+			idrive = <10>;
+			fin-sel = <2>;
+			inductance = <18>;
+		};
+	};
+};

samples/sensor/fdc2x1x/prj.conf

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+CONFIG_LOG=y
+CONFIG_I2C=y
+CONFIG_SENSOR=y
+CONFIG_PM_DEVICE=n
+CONFIG_NEWLIB_LIBC=y
+CONFIG_NEWLIB_LIBC_FLOAT_PRINTF=y
+
+CONFIG_FDC2X1X=y
+CONFIG_FDC2X1X_TRIGGER_GLOBAL_THREAD=n

samples/sensor/fdc2x1x/sample.yaml

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+sample:
+  name: fdc2x1x sample
+  description: FDC2X1X sample application
+tests:
+  sample.sensor.fdc2x1x:
+    harness: sensor
+    tags: sensors
+    platform_allow: nrf9160dk_nrf9160

samples/sensor/fdc2x1x/src/main.c

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+/*
+ * Copyright (c) 2020 arithmetics.io
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr.h>
+#include <device.h>
+#include <sys/util.h>
+#include <drivers/sensor.h>
+#include "drivers/sensor/fdc2x1x.h"
+#include <stdio.h>
+
+#define CH_BUF_INIT(m)          {},
+
+K_SEM_DEFINE(sem, 0, 1);
+
+#ifdef CONFIG_FDC2X1X_TRIGGER
+static void trigger_handler(const struct device *dev,
+			    struct sensor_trigger *trigger)
+{
+	switch (trigger->type) {
+	case SENSOR_TRIG_DATA_READY:
+		if (sensor_sample_fetch(dev)) {
+			printk("Sample fetch error\n");
+			return;
+		}
+		k_sem_give(&sem);
+		break;
+	default:
+		printk("Unknown trigger\n");
+	}
+}
+#endif
+
+#ifdef CONFIG_PM_DEVICE
+static void pm_cb(const struct device *dev,
+		  int status,
+		  void *context,
+		  void *arg)
+{
+	ARG_UNUSED(dev);
+	ARG_UNUSED(arg);
+
+	switch (*(uint32_t *)context) {
+	case DEVICE_PM_ACTIVE_STATE:
+		printk("Enter ACTIVE_STATE ");
+		break;
+	case DEVICE_PM_LOW_POWER_STATE:
+		printk("Enter LOW_POWER_STATE ");
+		break;
+	case DEVICE_PM_OFF_STATE:
+		printk("Enter OFF_STATE ");
+		break;
+	}
+
+	if (status) {
+		printk("Fail\n");
+	} else {
+		printk("Success\n");
+	}
+}
+#endif
+
+void main(void)
+{
+	struct sensor_value ch_buf[] = {
+		DT_FOREACH_CHILD(DT_INST(0, ti_fdc2x1x), CH_BUF_INIT)
+	};
+
+	uint8_t num_ch = ARRAY_SIZE(ch_buf);
+	enum sensor_channel base;
+	int i;
+
+	const struct device *dev =
+		device_get_binding(DT_LABEL(DT_INST(0, ti_fdc2x1x)));
+
+	if (dev == NULL) {
+		printk("Could not get %s device\n",
+		       DT_LABEL(DT_INST(0, ti_fdc2x1x)));
+		return;
+	}
+
+#ifdef CONFIG_FDC2X1X_TRIGGER
+	struct sensor_trigger trig = {
+		.type = SENSOR_TRIG_DATA_READY,
+		.chan = SENSOR_CHAN_ALL,
+	};
+
+	if (sensor_trigger_set(dev, &trig, trigger_handler)) {
+		printk("Could not set trigger\n");
+		return;
+	}
+#endif
+
+#ifdef CONFIG_PM_DEVICE
+	/* Testing the power modes */
+	uint32_t p_state;
+
+	p_state = DEVICE_PM_LOW_POWER_STATE;
+	device_set_power_state(dev, p_state, pm_cb, NULL);
+
+	p_state = DEVICE_PM_OFF_STATE;
+	device_set_power_state(dev, p_state, pm_cb, NULL);
+
+	p_state = DEVICE_PM_ACTIVE_STATE;
+	device_set_power_state(dev, p_state, pm_cb, NULL);
+#endif
+
+	while (1) {
+#ifdef CONFIG_FDC2X1X_TRIGGER
+		k_sem_take(&sem, K_FOREVER);
+#else
+		if (sensor_sample_fetch(dev) < 0) {
+			printk("Sample fetch failed\n");
+			return;
+		}
+#endif
+		base = SENSOR_CHAN_FDC2X1X_FREQ_CH0;
+		for (i = 0; i < num_ch; i++) {
+			sensor_channel_get(dev, base++, &ch_buf[i]);
+			printf("ch%d: %f MHz ", i, sensor_value_to_double(&ch_buf[i]));
+		}
+		printf("\n");
+
+		base = SENSOR_CHAN_FDC2X1X_CAPACITANCE_CH0;
+		for (i = 0; i < num_ch; i++) {
+			sensor_channel_get(dev, base++, &ch_buf[i]);
+			printf("ch%d: %f pF ", i, sensor_value_to_double(&ch_buf[i]));
+		}
+		printf("\n\n");
+
+
+#ifdef CONFIG_PM_DEVICE
+		p_state = DEVICE_PM_OFF_STATE;
+		device_set_power_state(dev, p_state, pm_cb, NULL);
+		k_sleep(K_MSEC(2000));
+		p_state = DEVICE_PM_ACTIVE_STATE;
+		device_set_power_state(dev, p_state, pm_cb, NULL);
+#elif CONFIG_FDC2X1X_TRIGGER_NONE
+		k_sleep(K_MSEC(100));
+#endif
+	}
+}