adxl345: Add support for adxl345 accelerometer

Add support for taking measurements from an adxl345 accelerometer via
SPI interface.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>

2 files changed, 180 insertions, 1 deletions

diff --git a/src/Makefile b/src/Makefile
index 92be64e2..98c9a1c1 100644
--- a/src/Makefile
+++ b/src/Makefile
@@ -7,4 +7,4 @@ src-$(CONFIG_HAVE_GPIO_SPI) += spicmds.c thermocouple.c
 src-$(CONFIG_HAVE_GPIO_I2C) += i2ccmds.c
 src-$(CONFIG_HAVE_GPIO_HARD_PWM) += pwmcmds.c
 src-$(CONFIG_HAVE_GPIO_BITBANGING) += lcd_st7920.c lcd_hd44780.c buttons.c \
-    tmcuart.c spi_software.c neopixel.c
+    tmcuart.c spi_software.c neopixel.c sensor_adxl345.c
diff --git a/src/sensor_adxl345.c b/src/sensor_adxl345.c
new file mode 100644
index 00000000..c76ab7db
--- /dev/null
+++ b/src/sensor_adxl345.c
@@ -0,0 +1,179 @@
+// Support for gathering acceleration data from ADXL345 chip
+//
+// Copyright (C) 2020  Kevin O'Connor <kevin@koconnor.net>
+//
+// This file may be distributed under the terms of the GNU GPLv3 license.
+
+#include <string.h> // memcpy
+#include "board/irq.h" // irq_disable
+#include "board/misc.h" // timer_read_time
+#include "basecmd.h" // oid_alloc
+#include "command.h" // DECL_COMMAND
+#include "sched.h" // DECL_TASK
+#include "spicmds.h" // spidev_transfer
+
+struct adxl345 {
+    struct timer timer;
+    uint32_t rest_ticks, stop_time;
+    struct spidev_s *spi;
+    uint16_t sequence, limit_count;
+    uint8_t flags, data_count;
+    uint8_t data[48];
+};
+
+enum {
+    AX_HAVE_START = 1<<0, AX_RUNNING = 1<<1, AX_PENDING = 1<<2,
+};
+
+static struct task_wake adxl345_wake;
+
+static uint_fast8_t
+adxl345_event(struct timer *timer)
+{
+    struct adxl345 *ax = container_of(timer, struct adxl345, timer);
+    ax->flags |= AX_PENDING;
+    sched_wake_task(&adxl345_wake);
+    return SF_DONE;
+}
+
+void
+command_config_adxl345(uint32_t *args)
+{
+    struct adxl345 *ax = oid_alloc(args[0], command_config_adxl345
+                                   , sizeof(*ax));
+    ax->timer.func = adxl345_event;
+    ax->spi = spidev_oid_lookup(args[1]);
+}
+DECL_COMMAND(command_config_adxl345, "config_adxl345 oid=%c spi_oid=%c");
+
+// Report local measurement buffer
+static void
+adxl_report(struct adxl345 *ax, uint8_t oid)
+{
+    sendf("adxl345_data oid=%c sequence=%hu data=%*s"
+          , oid, ax->sequence, ax->data_count, ax->data);
+    ax->data_count = 0;
+    ax->sequence++;
+}
+
+// Chip registers
+#define AR_POWER_CTL   0x2D
+#define AR_DATAX0      0x32
+#define AR_FIFO_STATUS 0x39
+#define AM_READ  0x80
+#define AM_MULTI 0x40
+
+// Query accelerometer data
+static void
+adxl_query(struct adxl345 *ax, uint8_t oid)
+{
+    uint8_t msg[9] = { AR_DATAX0 | AM_READ | AM_MULTI, 0, 0, 0, 0, 0, 0, 0, 0 };
+    spidev_transfer(ax->spi, 1, sizeof(msg), msg);
+    memcpy(&ax->data[ax->data_count], &msg[1], 6);
+    ax->data_count += 6;
+    if (ax->data_count + 6 > ARRAY_SIZE(ax->data))
+        adxl_report(ax, oid);
+    uint_fast8_t fifo_status = msg[8] & ~0x80; // Ignore trigger bit
+    if (fifo_status >= 31 && ax->limit_count != 0xffff)
+        ax->limit_count++;
+    if (fifo_status > 1 && fifo_status <= 32) {
+        // More data in fifo - wake this task again
+        sched_wake_task(&adxl345_wake);
+    } else if (ax->flags & AX_RUNNING) {
+        // Sleep until next check time
+        sched_del_timer(&ax->timer);
+        ax->flags &= ~AX_PENDING;
+        irq_disable();
+        ax->timer.waketime = timer_read_time() + ax->rest_ticks;
+        sched_add_timer(&ax->timer);
+        irq_enable();
+    }
+}
+
+// Startup measurements
+static void
+adxl_start(struct adxl345 *ax, uint8_t oid)
+{
+    sched_del_timer(&ax->timer);
+    ax->flags = AX_RUNNING;
+    uint8_t msg[2] = { AR_POWER_CTL, 0x08 };
+    uint32_t start1_time = timer_read_time();
+    spidev_transfer(ax->spi, 0, sizeof(msg), msg);
+    irq_disable();
+    uint32_t start2_time = timer_read_time();
+    ax->timer.waketime = start2_time + ax->rest_ticks;
+    sched_add_timer(&ax->timer);
+    irq_enable();
+    sendf("adxl345_start oid=%c start1_time=%u start2_time=%u"
+          , oid, start1_time, start2_time);
+}
+
+// End measurements
+static void
+adxl_stop(struct adxl345 *ax, uint8_t oid)
+{
+    // Disable measurements
+    sched_del_timer(&ax->timer);
+    ax->flags = 0;
+    uint8_t msg[2] = { AR_POWER_CTL, 0x00 };
+    uint32_t end1_time = timer_read_time();
+    spidev_transfer(ax->spi, 0, sizeof(msg), msg);
+    uint32_t end2_time = timer_read_time();
+    // Drain any measurements still in fifo
+    uint_fast8_t i;
+    for (i=0; i<33; i++) {
+        msg[0] = AR_FIFO_STATUS | AM_READ;
+        msg[1] = 0;
+        spidev_transfer(ax->spi, 1, sizeof(msg), msg);
+        if (!(msg[1] & 0x3f))
+            break;
+        adxl_query(ax, oid);
+    }
+    // Report final data
+    if (ax->data_count)
+        adxl_report(ax, oid);
+    sendf("adxl345_end oid=%c end1_time=%u end2_time=%u"
+          " limit_count=%hu sequence=%hu"
+          , oid, end1_time, end2_time, ax->limit_count, ax->sequence);
+}
+
+void
+command_query_adxl345(uint32_t *args)
+{
+    struct adxl345 *ax = oid_lookup(args[0], command_config_adxl345);
+
+    if (!args[2]) {
+        // End measurements
+        adxl_stop(ax, args[0]);
+        return;
+    }
+    // Start new measurements query
+    sched_del_timer(&ax->timer);
+    ax->timer.waketime = args[1];
+    ax->rest_ticks = args[2];
+    ax->flags = AX_HAVE_START;
+    ax->sequence = ax->limit_count = 0;
+    ax->data_count = 0;
+    sched_add_timer(&ax->timer);
+}
+DECL_COMMAND(command_query_adxl345,
+             "query_adxl345 oid=%c clock=%u rest_ticks=%u");
+
+void
+adxl345_task(void)
+{
+    if (!sched_check_wake(&adxl345_wake))
+        return;
+    uint8_t oid;
+    struct adxl345 *ax;
+    foreach_oid(oid, ax, command_config_adxl345) {
+        uint_fast8_t flags = ax->flags;
+        if (!(flags & AX_PENDING))
+            continue;
+        if (flags & AX_HAVE_START)
+            adxl_start(ax, oid);
+        else
+            adxl_query(ax, oid);
+    }
+}
+DECL_TASK(adxl345_task);