[RFC] periph/pdm: propose API and add nrf52 implementation

boards/adafruit-clue/Makefile.features

@@ -2,6 +2,7 @@ CPU_MODEL = nrf52840xxaa
 
 # Put defined MCU peripherals here (in alphabetical order)
 FEATURES_PROVIDED += periph_i2c
+FEATURES_PROVIDED += periph_pdm
 FEATURES_PROVIDED += periph_spi
 FEATURES_PROVIDED += periph_uart
 FEATURES_PROVIDED += periph_usbdev

boards/adafruit-clue/include/periph_conf.h

@@ -95,6 +95,16 @@ static const spi_conf_t spi_config[] = {
 #define SPI_NUMOF           ARRAY_SIZE(spi_config)
 /** @} */
 
+/**
+ * @name    PDM configuration
+ * @{
+ */
+static const pdm_conf_t pdm_config = {
+    .din_pin = GPIO_PIN(0, 0),
+    .clk_pin = GPIO_PIN(0, 1),
+};
+/** @} */
+
 #ifdef __cplusplus
 }
 #endif

cpu/nrf52/include/periph_cpu.h

@@ -257,6 +257,15 @@ void spi_twi_irq_register_spi(NRF_SPIM_Type *bus,
  */
 void spi_twi_irq_register_i2c(NRF_TWIM_Type *bus,
                               spi_twi_irq_cb_t cb, void *arg);
+
+/**
+ * @brief   Structure for PDM configuration data
+ */
+typedef struct {
+    uint8_t din_pin;         /**< DIN pin */
+    uint8_t clk_pin;         /**< CLK pin */
+} pdm_conf_t;
+
 #ifdef __cplusplus
 }
 #endif

cpu/nrf52/periph/pdm.c

@@ -0,0 +1,167 @@
+/*
+ * Copyright (C) 2020 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     cpu_nrf52
+ * @{
+ *
+ * @file
+ * @brief       Implementation of the peripheral PDM interface
+ *
+ * @author      Alexandre Abadie <[email protected]>
+ *
+ * @}
+ */
+
+#include <assert.h>
+#include <errno.h>
+#include <inttypes.h>
+
+#include "cpu.h"
+#include "periph/gpio.h"
+#include "periph/pdm.h"
+
+#define ENABLE_DEBUG    (0)
+#include "debug.h"
+
+/* The samples buffer is a double buffer */
+int16_t _pdm_buf[PDM_BUF_SIZE * 2] = { 0 };
+static uint8_t _pdm_current_buf = 0;
+static pdm_isr_ctx_t isr_ctx;
+
+int pdm_init(pdm_mode_t mode, pdm_sample_rate_t rate, int8_t gain,
+              pdm_data_cb_t cb, void *arg)
+{
+    if (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {
+        NRF_CLOCK->TASKS_HFCLKSTART = 1;
+        while (NRF_CLOCK->EVENTS_HFCLKSTARTED == 0) {}
+    }
+
+    /* Configure sampling rate */
+    switch (rate) {
+        case PDM_SAMPLE_RATE_16KHZ:
+#ifdef CPU_MODEL_NRF52840XXAA
+            NRF_PDM->RATIO = ((PDM_RATIO_RATIO_Ratio80 << PDM_RATIO_RATIO_Pos) & PDM_RATIO_RATIO_Msk);
+            NRF_PDM->PDMCLKCTRL = PDM_PDMCLKCTRL_FREQ_1280K;
+#else
+            NRF_PDM->PDMCLKCTRL = PDM_PDMCLKCTRL_FREQ_Default; /* 1.033MHz */
+#endif
+            break;
+        case PDM_SAMPLE_RATE_20KHZ:
+            NRF_PDM->PDMCLKCTRL = 0x0A000000; /* CLK= 1.280 MHz (32 MHz / 25) => rate= 20000 Hz */
+            break;
+        case PDM_SAMPLE_RATE_41KHZ:
+            NRF_PDM->PDMCLKCTRL = 0x15000000; /* CLK= 2.667 MHz (32 MHz / 12) => rate= 41667 Hz */
+            break;
+        case PDM_SAMPLE_RATE_50KHZ:
+            NRF_PDM->PDMCLKCTRL = 0x19000000; /* CLK= 3.200 MHz (32 MHz / 10) => rate= 50000 Hz */
+            break;
+        case PDM_SAMPLE_RATE_60KHZ:
+            NRF_PDM->PDMCLKCTRL = 0x20000000; /* CLK= 4.000 MHz (32 MHz / 8) => rate= 60000 Hz */
+            break;
+        default:
+            DEBUG("[pdm] init: sample rate not supported\n");
+            return -ENOTSUP;
+    }
+
+    /* Configure mode (Mono or Stereo) */
+    switch (mode) {
+        case PDM_MODE_MONO:
+            NRF_PDM->MODE = PDM_MODE_OPERATION_Mono;
+            break;
+        case PDM_MODE_STEREO:
+            NRF_PDM->MODE = PDM_MODE_OPERATION_Stereo;
+            break;
+        default:
+            DEBUG("[pdm] init: mode not supported\n");
+            return -ENOTSUP;
+    }
+
+    /* Configure gain */
+    if (gain > PDM_GAIN_MAX) {
+        gain = PDM_GAIN_MAX;
+    }
+
+    if (gain < PDM_GAIN_MIN) {
+        gain = PDM_GAIN_MIN;
+    }
+
+    NRF_PDM->GAINR = (gain << 1) + 40;
+    NRF_PDM->GAINL = (gain << 1) + 40;
+
+    /* Configure CLK and DIN pins */
+    gpio_init(pdm_config.clk_pin, GPIO_OUT);
+    gpio_clear(pdm_config.clk_pin);
+    gpio_init(pdm_config.din_pin, GPIO_IN);
+
+    NRF_PDM->PSEL.CLK = pdm_config.clk_pin;
+    NRF_PDM->PSEL.DIN = pdm_config.din_pin;
+
+    /* clear pending events */
+    NRF_PDM->EVENTS_STARTED = 0;
+    NRF_PDM->EVENTS_STOPPED = 0;
+    NRF_PDM->EVENTS_END = 0;
+
+    /* Enable end/started/stopped events */
+    NRF_PDM->INTENSET = ((PDM_INTEN_END_Enabled << PDM_INTEN_END_Pos) |
+                        (PDM_INTEN_STARTED_Enabled << PDM_INTEN_STARTED_Pos) |
+                        (PDM_INTEN_STOPPED_Enabled << PDM_INTEN_STOPPED_Pos));
+
+    /* Configure internal RAM buffer size, divide by 2 for stereo mode */
+    NRF_PDM->SAMPLE.MAXCNT = (PDM_BUF_SIZE >> mode);
+
+    isr_ctx.cb = cb;
+    isr_ctx.arg = arg;
+
+    /* enable interrupt */
+    NVIC_EnableIRQ(PDM_IRQn);
+
+    /* Enable PDM */
+    NRF_PDM->ENABLE = (PDM_ENABLE_ENABLE_Enabled << PDM_ENABLE_ENABLE_Pos);
+
+    return 0;
+}
+
+void pdm_start(void)
+{
+    NRF_PDM->SAMPLE.PTR = (uint32_t)_pdm_buf;
+    DEBUG("[PDM] MAXCNT: %lu\n", NRF_PDM->SAMPLE.MAXCNT);
+
+    NRF_PDM->TASKS_START = 1;
+}
+
+void pdm_stop(void)
+{
+    NRF_PDM->TASKS_STOP = 1;
+}
+
+void isr_pdm(void)
+{
+    if (NRF_PDM->EVENTS_STARTED == 1) {
+        NRF_PDM->EVENTS_STARTED = 0;
+        uint8_t next_buf_pos = (_pdm_current_buf + 1) & 0x1;
+        NRF_PDM->SAMPLE.PTR = (uint32_t)&_pdm_buf[next_buf_pos * (PDM_BUF_SIZE >> 1)];
+    }
+
+    if (NRF_PDM->EVENTS_STOPPED == 1) {
+        NRF_PDM->EVENTS_STOPPED = 0;
+        _pdm_current_buf = 0;
+    }
+
+    if (NRF_PDM->EVENTS_END == 1) {
+        NRF_PDM->EVENTS_END = 0;
+
+        /* Process received samples frame */
+        isr_ctx.cb(isr_ctx.arg, &_pdm_buf[_pdm_current_buf * (PDM_BUF_SIZE >> 1)]);
+
+        /* Set next buffer */
+        _pdm_current_buf = (_pdm_current_buf + 1) & 0x1;
+    }
+
+    cortexm_isr_end();
+}

drivers/include/periph/pdm.h

@@ -0,0 +1,127 @@
+/*
+ * Copyright (C) 2020 Inria
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup    drivers_periph_pdm Pulse Density Modulation (PDM) driver
+ * @ingroup     drivers_periph
+ * @brief       Low-level Pulse Density Modulation (PDM) driver
+ *
+ * @{
+ * @file
+ *
+ * @author      Alexandre Abadie <[email protected]>
+ *
+ */
+
+#ifndef PERIPH_PDM_H
+#define PERIPH_PDM_H
+
+#include <stdint.h>
+
+#include "periph_cpu.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief   Default PDM mode values
+ * @{
+ */
+#ifndef HAVE_PDM_MODE_T
+typedef enum {
+    PDM_MODE_MONO = 0,      /**< Mono mode */
+    PDM_MODE_STEREO,        /**< Stereo mode */
+} pdm_mode_t;
+#endif
+/** @} */
+
+/**
+ * @brief   Default PDM sampling rate values
+ * @{
+ */
+#ifndef HAVE_PDM_SAMPLE_RATE_T
+typedef enum {
+    PDM_SAMPLE_RATE_16KHZ = 0,      /**< 16kHz */
+    PDM_SAMPLE_RATE_20KHZ,          /**< 20kHz */
+    PDM_SAMPLE_RATE_41KHZ,          /**< 41.6kHz */
+    PDM_SAMPLE_RATE_50KHZ,          /**< 50kHz */
+    PDM_SAMPLE_RATE_60KHZ,          /**< 60kHz */
+} pdm_sample_rate_t;
+#endif
+/** @} */
+
+/**
+ * @brief   Default PDM min gain values (in dB)
+ */
+#ifndef PDM_GAIN_MIN
+#define PDM_GAIN_MIN        (-20)
+#endif
+
+/**
+ * @brief   Default PDM max gain values (in dB)
+ */
+#ifndef PDM_GAIN_MAX
+#define PDM_GAIN_MAX        (20)
+#endif
+
+/**
+ * @brief   Default PDM samples frame buffer size
+ */
+#ifndef PDM_BUF_SIZE
+#define PDM_BUF_SIZE        (128U)
+#endif
+
+/**
+ * @brief   Signature for data received interrupt callback
+ *
+ * @param[in] arg           context to the callback (optional)
+ * @param[in] buf           the buffer containing the current samples frame
+ */
+typedef void(*pdm_data_cb_t)(void *arg, int16_t *buf);
+
+/**
+ * @brief   Interrupt context for a PDM device
+ */
+#ifndef HAVE_PDM_ISR_CTX_T
+typedef struct {
+    pdm_data_cb_t cb;       /**< data received interrupt callback */
+    void *arg;              /**< argument to both callback routines */
+} pdm_isr_ctx_t;
+#endif
+
+/**
+ * @brief   Initialize the PDM peripheral
+ *
+ * @param[in] rate      sample rate
+ * @param[in] gain      gain
+ * @param[in] cb        data received callback function
+ * @param[in] arg       context passed to the callback function
+ *
+ * @return  0 on successful initialization
+ * @return <0 on error
+ */
+int pdm_init(pdm_mode_t mode, pdm_sample_rate_t rate, int8_t gain,
+             pdm_data_cb_t cb, void *arg);
+
+/**
+ * @brief   Start the PDM peripheral
+ */
+void pdm_start(void);
+
+/**
+ * @brief   Stop the PDM peripheral
+ */
+void pdm_stop(void);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* PERIPH_PDM_H */
+/** @} */

tests/periph_pdm/Makefile

@@ -0,0 +1,5 @@
+include ../Makefile.tests_common
+
+FEATURES_REQUIRED = periph_pdm
+
+include $(RIOTBASE)/Makefile.include