drivers: input: Implement driver for ADC keys
This commit introduces a driver for ADC keys, a common circuit design where
keys are connected to an ADC input via a resistor ladder.
Signed-off-by: Chen Xingyu <hi@xingrz.me>
diff --git a/drivers/input/CMakeLists.txt b/drivers/input/CMakeLists.txt
index 9aeb919..22eca7b 100644
--- a/drivers/input/CMakeLists.txt
+++ b/drivers/input/CMakeLists.txt
@@ -4,6 +4,7 @@
zephyr_library_property(ALLOW_EMPTY TRUE)
# zephyr-keep-sorted-start
+zephyr_library_sources_ifdef(CONFIG_INPUT_ADC_KEYS input_adc_keys.c)
zephyr_library_sources_ifdef(CONFIG_INPUT_ANALOG_AXIS input_analog_axis.c)
zephyr_library_sources_ifdef(CONFIG_INPUT_ANALOG_AXIS_SETTINGS input_analog_axis_settings.c)
zephyr_library_sources_ifdef(CONFIG_INPUT_CAP1203 input_cap1203.c)
diff --git a/drivers/input/Kconfig b/drivers/input/Kconfig
index 41c9324..a61fd94 100644
--- a/drivers/input/Kconfig
+++ b/drivers/input/Kconfig
@@ -6,6 +6,7 @@
menu "Input drivers"
# zephyr-keep-sorted-start
+source "drivers/input/Kconfig.adc_keys"
source "drivers/input/Kconfig.analog_axis"
source "drivers/input/Kconfig.cap1203"
source "drivers/input/Kconfig.cst816s"
diff --git a/drivers/input/Kconfig.adc_keys b/drivers/input/Kconfig.adc_keys
new file mode 100644
index 0000000..75415b4
--- /dev/null
+++ b/drivers/input/Kconfig.adc_keys
@@ -0,0 +1,10 @@
+# Copyright (c) 2024 Chen Xingyu <hi@xingrz.me>
+# SPDX-License-Identifier: Apache-2.0
+
+config INPUT_ADC_KEYS
+ bool "ADC attached resistor ladder buttons"
+ default y
+ depends on DT_HAS_ADC_KEYS_ENABLED
+ depends on ADC
+ help
+ Enable support for ADC attached resistor ladder buttons.
diff --git a/drivers/input/input_adc_keys.c b/drivers/input/input_adc_keys.c
new file mode 100644
index 0000000..2e24ffd
--- /dev/null
+++ b/drivers/input/input_adc_keys.c
@@ -0,0 +1,232 @@
+/*
+ * Copyright (c) 2024 Chen Xingyu <hi@xingrz.me>
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+#define DT_DRV_COMPAT adc_keys
+
+#include <stdlib.h>
+#include <stdbool.h>
+
+#include <zephyr/device.h>
+#include <zephyr/drivers/adc.h>
+#include <zephyr/input/input.h>
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
+#include <zephyr/sys/util.h>
+
+LOG_MODULE_REGISTER(adc_keys, CONFIG_INPUT_LOG_LEVEL);
+
+struct adc_keys_code_config {
+ int32_t press_mv;
+ uint8_t key_index;
+};
+
+struct adc_keys_key_state {
+ bool last_state;
+ bool curr_state;
+};
+
+struct adc_keys_config {
+ struct adc_dt_spec channel;
+ uint32_t sample_period_ms;
+ int32_t keyup_mv;
+ const struct adc_keys_code_config *code_cfg;
+ const uint16_t *key_code;
+ struct adc_keys_key_state *key_state;
+ uint8_t code_cnt;
+ uint8_t key_cnt;
+};
+
+struct adc_keys_data {
+ const struct device *self;
+ struct k_work_delayable dwork;
+ struct adc_sequence seq;
+};
+
+static inline int32_t adc_keys_read(const struct device *dev)
+{
+ const struct adc_keys_config *cfg = dev->config;
+ struct adc_keys_data *data = dev->data;
+ uint16_t sample_raw;
+ int32_t sample_mv;
+ int ret;
+
+ data->seq.buffer = &sample_raw;
+ data->seq.buffer_size = sizeof(sample_raw);
+
+ ret = adc_read(cfg->channel.dev, &data->seq);
+ if (ret) {
+ LOG_ERR("ADC read failed %d", ret);
+ return cfg->keyup_mv;
+ }
+
+ sample_mv = (int32_t)sample_raw;
+ adc_raw_to_millivolts_dt(&cfg->channel, &sample_mv);
+
+ return sample_mv;
+}
+
+static inline void adc_keys_process(const struct device *dev)
+{
+ const struct adc_keys_config *cfg = dev->config;
+ int32_t sample_mv, closest_mv;
+ uint32_t diff, closest_diff = UINT32_MAX;
+ const struct adc_keys_code_config *code_cfg;
+ struct adc_keys_key_state *key_state;
+ uint16_t key_code;
+
+ sample_mv = adc_keys_read(dev);
+
+ /*
+ * Find the closest key press threshold to the sample value.
+ */
+
+ for (uint8_t i = 0; i < cfg->code_cnt; i++) {
+ diff = abs(sample_mv - cfg->code_cfg[i].press_mv);
+ if (diff < closest_diff) {
+ closest_diff = diff;
+ closest_mv = cfg->code_cfg[i].press_mv;
+ }
+ }
+
+ diff = abs(sample_mv - cfg->keyup_mv);
+ if (diff < closest_diff) {
+ closest_diff = diff;
+ closest_mv = cfg->keyup_mv;
+ }
+
+ LOG_DBG("sample=%d mV, closest=%d mV, diff=%d mV", sample_mv, closest_mv, closest_diff);
+
+ /*
+ * Update cached key states according to the closest key press threshold.
+ *
+ * Note that multiple keys may have the same press threshold, which is
+ * the mixed voltage that these keys are simultaneously pressed.
+ */
+
+ for (uint8_t i = 0; i < cfg->code_cnt; i++) {
+ code_cfg = &cfg->code_cfg[i];
+ key_state = &cfg->key_state[code_cfg->key_index];
+
+ /*
+ * Only update curr_state if the key is pressed to prevent
+ * being overwritten by another threshold configuration.
+ */
+ if (closest_mv == code_cfg->press_mv) {
+ key_state->curr_state = true;
+ }
+ }
+
+ /*
+ * Report the key event if the key state has changed.
+ */
+
+ for (uint8_t i = 0; i < cfg->key_cnt; i++) {
+ key_state = &cfg->key_state[i];
+ key_code = cfg->key_code[i];
+
+ if (key_state->last_state != key_state->curr_state) {
+ LOG_DBG("Report event %s %d, code=%d", dev->name, key_state->curr_state,
+ key_code);
+ input_report_key(dev, key_code, key_state->curr_state, true, K_FOREVER);
+ key_state->last_state = key_state->curr_state;
+ }
+
+ /*
+ * Reset the state so that it can be updated in the next
+ * iteration.
+ */
+ key_state->curr_state = false;
+ }
+}
+
+static void adc_keys_work_handler(struct k_work *work)
+{
+ struct k_work_delayable *dwork = k_work_delayable_from_work(work);
+ struct adc_keys_data *data = CONTAINER_OF(dwork, struct adc_keys_data, dwork);
+ const struct device *dev = data->self;
+ const struct adc_keys_config *cfg = dev->config;
+
+ adc_keys_process(dev);
+
+ k_work_schedule(&data->dwork, K_MSEC(cfg->sample_period_ms));
+}
+
+static int adc_keys_init(const struct device *dev)
+{
+ const struct adc_keys_config *cfg = dev->config;
+ struct adc_keys_data *data = dev->data;
+ int ret;
+
+ if (!adc_is_ready_dt(&cfg->channel)) {
+ LOG_ERR("ADC controller device %s not ready", cfg->channel.dev->name);
+ return -ENODEV;
+ }
+
+ ret = adc_channel_setup_dt(&cfg->channel);
+ if (ret) {
+ LOG_ERR("ADC channel setup failed %d", ret);
+ return ret;
+ }
+
+ ret = adc_sequence_init_dt(&cfg->channel, &data->seq);
+ if (ret) {
+ LOG_ERR("ADC sequence init failed %d", ret);
+ return ret;
+ }
+
+ data->self = dev;
+ k_work_init_delayable(&data->dwork, adc_keys_work_handler);
+
+ if (IS_ENABLED(CONFIG_INPUT_LOG_LEVEL_DBG)) {
+ for (uint8_t i = 0; i < cfg->code_cnt; i++) {
+ LOG_DBG("* code %d: key_index=%d threshold=%d mV code=%d", i,
+ cfg->code_cfg[i].key_index, cfg->code_cfg[i].press_mv,
+ cfg->key_code[cfg->code_cfg[i].key_index]);
+ }
+ }
+
+ k_work_schedule(&data->dwork, K_MSEC(cfg->sample_period_ms));
+
+ return 0;
+}
+
+#define ADC_KEYS_CODE_CFG_ITEM(node_id, prop, idx) \
+ { \
+ .key_index = DT_NODE_CHILD_IDX(node_id) /* include disabled nodes */, \
+ .press_mv = DT_PROP_BY_IDX(node_id, prop, idx), \
+ }
+
+#define ADC_KEYS_CODE_CFG(node_id) \
+ DT_FOREACH_PROP_ELEM_SEP(node_id, press_thresholds_mv, ADC_KEYS_CODE_CFG_ITEM, (,))
+
+#define ADC_KEYS_KEY_CODE(node_id) DT_PROP(node_id, zephyr_code)
+
+#define ADC_KEYS_INST(n) \
+ static struct adc_keys_data adc_keys_data_##n; \
+ \
+ static const struct adc_keys_code_config adc_keys_code_cfg_##n[] = { \
+ DT_INST_FOREACH_CHILD_STATUS_OKAY_SEP(n, ADC_KEYS_CODE_CFG, (,))}; \
+ \
+ static const uint16_t adc_keys_key_code_##n[] = { \
+ DT_INST_FOREACH_CHILD_SEP(n, ADC_KEYS_KEY_CODE, (,))}; \
+ \
+ static struct adc_keys_key_state \
+ adc_keys_key_state_##n[ARRAY_SIZE(adc_keys_key_code_##n)]; \
+ \
+ static const struct adc_keys_config adc_keys_cfg_##n = { \
+ .channel = ADC_DT_SPEC_INST_GET(n), \
+ .sample_period_ms = DT_INST_PROP(n, sample_period_ms), \
+ .keyup_mv = DT_INST_PROP(n, keyup_threshold_mv), \
+ .code_cfg = adc_keys_code_cfg_##n, \
+ .key_code = adc_keys_key_code_##n, \
+ .key_state = adc_keys_key_state_##n, \
+ .code_cnt = ARRAY_SIZE(adc_keys_code_cfg_##n), \
+ .key_cnt = ARRAY_SIZE(adc_keys_key_code_##n), \
+ }; \
+ \
+ DEVICE_DT_INST_DEFINE(n, adc_keys_init, NULL, &adc_keys_data_##n, &adc_keys_cfg_##n, \
+ POST_KERNEL, CONFIG_INPUT_INIT_PRIORITY, NULL);
+
+DT_INST_FOREACH_STATUS_OKAY(ADC_KEYS_INST)
diff --git a/dts/bindings/input/adc-keys.yaml b/dts/bindings/input/adc-keys.yaml
new file mode 100644
index 0000000..022f2f4
--- /dev/null
+++ b/dts/bindings/input/adc-keys.yaml
@@ -0,0 +1,70 @@
+# Copyright (c) 2024 Chen Xingyu <hi@xingrz.me>
+# SPDX-License-Identifier: Apache-2.0
+
+description: |
+ Input driver for ADC attached resistor ladder buttons.
+
+ The driver itself does not calculate each possible combination of resistor
+ values. Instead, users are required to specify the voltage for each single
+ key press or for combinations of key presses.
+
+ Example:
+
+ #include <dt-bindings/input/input-event-codes.h>
+
+ / {
+ buttons {
+ compatible = "adc-keys";
+ io-channels = <&adc 2>;
+ keyup-threshold-mv = <0>;
+
+ key_0 {
+ press-thresholds-mv = <1650>, /* KEY0 */
+ <2536>; /* KEY0 + KEY1 */
+ zephyr,code = <INPUT_KEY_0>;
+ };
+
+ key_1 {
+ press-thresholds-mv = <2300>, /* KEY1 */
+ <2536>; /* KEY0 + KEY1 */
+ zephyr,code = <INPUT_KEY_1>;
+ };
+ };
+ };
+
+compatible: "adc-keys"
+
+include: base.yaml
+
+properties:
+ io-channels:
+ type: phandle-array
+ required: true
+ description: Phandle to an ADC channel.
+
+ sample-period-ms:
+ type: int
+ default: 20
+ description: |
+ Sample period in milliseconds.
+ If not specified defaults to 20.
+
+ keyup-threshold-mv:
+ type: int
+ required: true
+ description: |
+ Millivolt value to which all the keys are considered up.
+
+child-binding:
+ description: ADC KEYS child node.
+ properties:
+ press-thresholds-mv:
+ type: array
+ required: true
+ description: |
+ Array of millivolt values to consider a key pressed.
+
+ zephyr,code:
+ type: int
+ required: true
+ description: Key code to emit.
