samples: boards: firmware for Twinkie V2

sample firmware for Twinkie V2 that toggles the LED based on charging
status.

Signed-off-by: Jason Yuan <jasonyuan@google.com>

samples/boards/google_twinkie_v2_pda/CMakeLists.txt

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+# SPDX-License-Identifier: Apache-2.0
+
+cmake_minimum_required(VERSION 3.20.0)
+
+find_package(Zephyr REQUIRED HINTS $ENV{ZEPHYR_BASE})
+project(google_twinkie_v2)
+
+FILE(GLOB app_sources src/*.c)
+target_sources(app PRIVATE ${app_sources})

samples/boards/google_twinkie_v2_pda/README.rst

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+.. _google_twinkie_v2_pda:
+
+Twinkie Power Delivery
+######################
+
+Overview
+********
+
+This provides access to :ref:`Twinkie <google_twinkie_v2_board>` so you can try out
+the supported features.
+
+Building and Running
+********************
+
+Build and flash Twinkie as follows:
+
+.. zephyr-app-commands::
+   :zephyr-app: samples/boards/google_pda
+   :board: google_twinkie_v2
+   :goals: build flash
+   :compact:
+
+After flashing, the LED will start red. Putting the Twinkie in between any
+usbc connection will cause the LED to turn blue. The LED will turn green instead
+if the device is currently charging.

samples/boards/google_twinkie_v2_pda/prj.conf

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+CONFIG_ADC=y
+CONFIG_ADC_STM32=y
+CONFIG_GPIO=y
+CONFIG_LED=y

samples/boards/google_twinkie_v2_pda/sample.yaml

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+sample:
+  name: Twinkie V2 usb Vbus snooper
+tests:
+  sample.board.google_twinkie_v2:
+    platform_allow: google_twinkie_v2
+    tags: usb

samples/boards/google_twinkie_v2_pda/src/meas.c

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+/*
+ * Copyright (c) 2023 The ChromiumOS Authors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <stdio.h>
+#include <zephyr/kernel.h>
+#include <zephyr/drivers/adc.h>
+#include <zephyr/drivers/adc/voltage_divider.h>
+#include <zephyr/drivers/adc/current_sense_amplifier.h>
+
+/* The devicetree node identifier for the adc aliases. */
+#define VBUS_V_MEAS_NODE DT_ALIAS(vbus)
+#define VBUS_C_MEAS_NODE DT_ALIAS(cbus)
+
+static const struct voltage_divider_dt_spec adc_vbus_v =
+	VOLTAGE_DIVIDER_DT_SPEC_GET(VBUS_V_MEAS_NODE);
+static const struct current_sense_amplifier_dt_spec adc_vbus_c =
+	CURRENT_SENSE_AMPLIFIER_DT_SPEC_GET(VBUS_C_MEAS_NODE);
+
+int meas_vbus_v(int32_t *v)
+{
+	int ret;
+	int32_t sample_buffer = 0;
+
+	/* Structure defining an ADC sampling sequence */
+	struct adc_sequence sequence = {
+		.buffer = &sample_buffer,
+		/* buffer size in bytes, not number of samples */
+		.buffer_size = sizeof(sample_buffer),
+		.calibrate = true,
+	};
+	adc_sequence_init_dt(&adc_vbus_v.port, &sequence);
+
+	ret = adc_read(adc_vbus_v.port.dev, &sequence);
+	if (ret != 0) {
+		return ret;
+	}
+
+	*v = sample_buffer;
+	ret = adc_raw_to_millivolts_dt(&adc_vbus_v.port, v);
+	if (ret != 0) {
+		return ret;
+	}
+
+	ret = voltage_divider_scale_dt(&adc_vbus_v, v);
+	if (ret != 0) {
+		return ret;
+	}
+
+	return 0;
+}
+
+int meas_vbus_c(int32_t *c)
+{
+	int ret;
+	int32_t sample_buffer = 0;
+
+	/* Structure defining an ADC sampling sequence */
+	struct adc_sequence sequence = {
+		.buffer = &sample_buffer,
+		/* buffer size in bytes, not number of samples */
+		.buffer_size = sizeof(sample_buffer),
+		.calibrate = true,
+	};
+	adc_sequence_init_dt(&adc_vbus_c.port, &sequence);
+
+	ret = adc_read(adc_vbus_c.port.dev, &sequence);
+	if (ret != 0) {
+		return ret;
+	}
+
+	*c = sample_buffer;
+	ret = adc_raw_to_millivolts_dt(&adc_vbus_c.port, c);
+	if (ret != 0) {
+		return ret;
+	}
+
+	/* prescaling the voltage offset */
+	*c -= adc_vbus_c.port.vref_mv / 2;
+	current_sense_amplifier_scale_dt(&adc_vbus_c, c);
+
+	return 0;
+}
+
+int meas_init(void)
+{
+	int ret;
+
+	ret = adc_channel_setup_dt(&adc_vbus_v.port);
+	if (ret != 0) {
+		return ret;
+	}
+
+	ret = adc_channel_setup_dt(&adc_vbus_c.port);
+	if (ret != 0) {
+		return ret;
+	}
+
+	return 0;
+}

samples/boards/google_twinkie_v2_pda/src/meas.h

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+/*
+ * Copyright (c) 2023 The ChromiumOS Authors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#ifndef __MEAS_H__
+#define __MEAS_H__
+
+/**
+ * @brief Initializes the measurement module, sets up all the adc channels through the device tree
+ * binding
+ *
+ * @return 0 on success
+ */
+int meas_init(void);
+
+/**
+ * @brief Measure the voltage on VBUS
+ *
+ * @param v pointer where VBUS voltage, in millivolts, is stored
+ *
+ * @return 0 on success
+ */
+int meas_vbus_v(int32_t *v);
+
+/**
+ * @brief Measure the current on VBUS
+ *
+ * @param c pointer where VBUS current, in milliamperes, is stored
+ *
+ * @return 0 on success
+ */
+int meas_vbus_c(int32_t *c);
+
+#endif

samples/boards/google_twinkie_v2_pda/src/view.c

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+/*
+ * Copyright (c) 2023 The ChromiumOS Authors
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/led.h>
+#include <zephyr/kernel.h>
+
+#include "meas.h"
+
+enum led_color_t {
+	LED_RED,
+	LED_GREEN,
+	LED_BLUE,
+};
+
+static void set_led(const struct device *const led, enum led_color_t led_color)
+{
+	if (led_color != LED_RED) {
+		led_off(led, LED_RED);
+	}
+	if (led_color != LED_GREEN) {
+		led_off(led, LED_GREEN);
+	}
+	if (led_color != LED_BLUE) {
+		led_off(led, LED_BLUE);
+	}
+	led_on(led, led_color);
+}
+
+#define CHARGING_VOLTAGE 5000
+#define CHARGING_CURRENT 1000
+
+void main(void)
+{
+	meas_init();
+
+	const struct device *const led = DEVICE_DT_GET_ONE(gpio_leds);
+	int32_t vbus_v = 0;
+	int32_t vbus_c = 0;
+
+	if (!device_is_ready(led)) {
+		return;
+	}
+
+	while (1) {
+		meas_vbus_v(&vbus_v);
+		meas_vbus_c(&vbus_c);
+
+		if (vbus_v > CHARGING_VOLTAGE) {
+			if (vbus_c > CHARGING_CURRENT) {
+				set_led(led, LED_GREEN);
+			} else {
+				set_led(led, LED_BLUE);
+			}
+		} else {
+			set_led(led, LED_RED);
+		}
+
+		k_usleep(500);
+	}
+}