drivers/ltc4150: Allow tracking last minute charge

Implemented an example `ltc4150_recorder_t` implementation as a proof of concept
for the recorder API.

drivers/include/ltc4150.h

@@ -185,7 +185,7 @@ typedef struct {
      * @brief `NULL` or a `NULL`-terminated array of data recorders
      * @pre   If not `NULL`, the last element of the array must be `NULL`
      */
-    ltc4150_recorder_t **recorders;
+    const ltc4150_recorder_t **recorders;
     /**
      * @brief `NULL` or an array of the user defined data for each recorder
      * @pre   If @see ltc4150_params_t::recorders is not `NULL`, this must point
@@ -207,6 +207,35 @@ struct ltc4150_dev {
     uint32_t discharged;        /**< # of pulses for discharging (POL=low) */
 };
 
+/**
+ * @brief Data structure used by @ref ltc4150_last_minute
+ */
+typedef struct {
+    uint32_t last_rotate_sec;   /**< Time stamp of the last ring "rotation" */
+    /**
+     * @brief Pulses in charging direction recorded in the last minute
+     */
+    uint16_t charged;
+    /**
+     * @brief Pulses in discharging direction recorded in the last minute
+     */
+    uint16_t discharged;
+    /**
+     * @brief Ring-buffer to store charge information in 10 sec resolution
+     */
+    uint8_t buf_charged[7];
+    /**
+     * @brief As above, but in discharging direction
+     */
+    uint8_t buf_discharged[7];
+    uint8_t ring_pos;           /**< Position in the ring buffer */
+} ltc4150_last_minute_data_t;
+
+/**
+ * @brief Records the charge transferred within the last minute using
+ */
+extern const ltc4150_recorder_t ltc4150_last_minute;
+
 /**
  * @brief             Initialize the LTC4150 driver
  *
@@ -275,6 +304,42 @@ int ltc4150_charge(ltc4150_dev_t *dev, uint32_t *charged, uint32_t *discharged);
  */
 int ltc4150_avg_current(ltc4150_dev_t *dev, int16_t *dest);
 
+/**
+ * @brief                  Get the measured charge in the last minute
+ *
+ * @param dev              The LTC4150 device to read data from
+ * @param data             The data recorded by @ref ltc4150_last_minute
+ * @param[out] charged     The charge transferred in charging direction
+ * @param[out] discharged  The charge transferred in discharging direction
+ *
+ * @retval 0                Success
+ * @retval -EINVAL          Called with an invalid argument
+ *
+ * @warning The returned data may be outdated up to ten seconds
+ *
+ * Passing `NULL` for `charged` or `discharged` is allowed, if only one
+ * information is of interest.
+ */
+int ltc4150_last_minute_charge(ltc4150_dev_t *dev,
+                               ltc4150_last_minute_data_t *data,
+                               uint32_t *charged, uint32_t *discharged);
+
+/**
+ * @brief Convert the raw data (# pulses) acquired by the LTC4150 device to
+ *        charge information in millicoulomb
+ * @note  This function will make writing data recorders (see
+ *        @ref ltc4150_recorder_t) easier, but is not intended for end users
+ *
+ * @param dev                 LTC4150 device the data was received from
+ * @param[out] charged        Charge in charging direction is stored here
+ * @param[out] discharged     Charge in discharging direction is stored here
+ * @param[in] raw_charged     Number of pulses in charging direction
+ * @param[in] raw_discharged  Number of pulses in discharging direction
+ */
+void ltc4150_pulses2c(const ltc4150_dev_t *dev,
+                      uint32_t *charged, uint32_t *discharged,
+                      uint32_t raw_charged,
+                      uint32_t raw_discharged);
 #ifdef __cplusplus
 }
 #endif

drivers/ltc4150/ltc4150.c

@@ -139,20 +139,10 @@ int ltc4150_shutdown(ltc4150_dev_t *dev)
     return 0;
 }
 
-/**
- * @brief Convert the raw data (# pulses) acquired by the LTC4150 device to
- *        charge information in millicoulomb
- *
- * @param dev                 LTC4150 device the data was received from
- * @param[out] charged        Charge in charging direction is stored here
- * @param[out] discharged     Charge in discharging direction is stored here
- * @param[in] raw_charged     Number of pulses in charging direction
- * @param[in] raw_discharged  Number of pulses in discharging direction
- */
-static void get_coulomb(const ltc4150_dev_t *dev,
-                        uint32_t *charged, uint32_t *discharged,
-                        uint32_t raw_charged,
-                        uint32_t raw_discharged)
+void ltc4150_pulses2c(const ltc4150_dev_t *dev,
+                      uint32_t *charged, uint32_t *discharged,
+                      uint32_t raw_charged,
+                      uint32_t raw_discharged)
 {
     uint64_t tmp;
 
@@ -180,7 +170,7 @@ int ltc4150_charge(ltc4150_dev_t *dev, uint32_t *charged, uint32_t *discharged)
     }
 
     gpio_irq_disable(dev->params.interrupt);
-    get_coulomb(dev, charged, discharged, dev->charged, dev->discharged);
+    ltc4150_pulses2c(dev, charged, discharged, dev->charged, dev->discharged);
     gpio_irq_enable(dev->params.interrupt);
     return 0;
 }

drivers/ltc4150/ltc4150_last_minute.c

@@ -0,0 +1,95 @@
+/*
+ * Copyright 2019 Otto-von-Guericke-Universität Magdeburg
+ *
+ * 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     drivers_ltc4150
+ * @{
+ *
+ * @file
+ * @brief       Track the drawn charged of the last minute
+ * @author      Marian Buschsieweke <marian.buschsieweke@ovgu.de>
+ * @}
+ */
+
+#include <errno.h>
+#include <string.h>
+
+#include "ltc4150.h"
+#include "xtimer.h"
+
+static void init_or_reset(ltc4150_dev_t *dev, uint64_t now_usec, void *arg);
+static void pulse(ltc4150_dev_t *dev, ltc4150_dir_t dir, uint64_t now_usec,
+                  void *arg);
+
+const ltc4150_recorder_t ltc4150_last_minute = {
+    .reset = init_or_reset,
+    .pulse = pulse,
+};
+
+static void init_or_reset(ltc4150_dev_t *dev, uint64_t now_usec, void *arg)
+{
+    (void)dev;
+    ltc4150_last_minute_data_t *data = arg;
+
+    memset(data, 0, sizeof(ltc4150_last_minute_data_t));
+    data->last_rotate_sec = now_usec / US_PER_SEC;
+}
+
+static void update_ringbuffer(ltc4150_last_minute_data_t *data,
+                              uint64_t now_usec)
+{
+    uint32_t now_sec = (now_usec / US_PER_SEC);
+
+    /* Note: This expression should be correct even when time overflows */
+    while (now_sec - data->last_rotate_sec > 10) {
+        data->last_rotate_sec += 10;
+        data->charged += data->buf_charged[data->ring_pos];
+        data->discharged += data->buf_discharged[data->ring_pos];
+        if (++data->ring_pos >= sizeof(data->buf_charged)/sizeof(data->buf_charged[0])) {
+            data->ring_pos = 0;
+        }
+        data->charged -= data->buf_charged[data->ring_pos];
+        data->discharged -= data->buf_discharged[data->ring_pos];
+        data->buf_charged[data->ring_pos] = 0;
+        data->buf_discharged[data->ring_pos] = 0;
+    }
+}
+
+static void pulse(ltc4150_dev_t *dev, ltc4150_dir_t dir, uint64_t now_usec,
+                  void *arg)
+{
+    (void)dev;
+    ltc4150_last_minute_data_t *data = arg;
+    update_ringbuffer(data, now_usec);
+
+    switch (dir) {
+        case LTC4150_CHARGE:
+            data->buf_charged[data->ring_pos]++;
+            break;
+        default:
+        case LTC4150_DISCHARGE:
+            data->buf_discharged[data->ring_pos]++;
+            break;
+    }
+}
+
+int ltc4150_last_minute_charge(ltc4150_dev_t *dev,
+                               ltc4150_last_minute_data_t *d,
+                               uint32_t *charged, uint32_t *discharged)
+{
+    if (!dev || !d) {
+        return -EINVAL;
+    }
+
+    gpio_irq_disable(dev->params.interrupt);
+    update_ringbuffer(d, xtimer_now_usec64());
+    ltc4150_pulses2c(dev, charged, discharged, d->charged, d->discharged);
+    gpio_irq_enable(dev->params.interrupt);
+
+    return 0;
+}