Acceleration: Add support for SC7A20 chip

The FIFO buffer is used as well

Author: StarGate01

src/CMakeLists.txt

@@ -442,6 +442,7 @@ list(APPEND SOURCE_FILES
         drivers/Bma421.cpp
         drivers/Bma421_C/bma4.c
         drivers/Bma421_C/bma423.c
+        drivers/SC7A20.cpp
         components/battery/BatteryController.cpp
         components/ble/BleController.cpp
         components/ble/NotificationManager.cpp
@@ -510,6 +511,7 @@ list(APPEND RECOVERY_SOURCE_FILES
         drivers/Bma421.cpp
         drivers/Bma421_C/bma4.c
         drivers/Bma421_C/bma423.c
+        drivers/SC7A20.cpp
         components/battery/BatteryController.cpp
         components/ble/BleController.cpp
         components/ble/NotificationManager.cpp
@@ -624,6 +626,8 @@ set(INCLUDE_FILES
         drivers/Bma421.h
         drivers/Bma421_C/bma4.c
         drivers/Bma421_C/bma423.c
+        drivers/SC7A20.h
+        drivers/SC7A20_registers.h
         components/battery/BatteryController.h
         components/ble/BleController.h
         components/ble/NotificationManager.h

src/drivers/SC7A20.cpp

@@ -0,0 +1,89 @@
+#include "drivers/SC7A20.h"
+#include "drivers/SC7A20_registers.h"
+#include <libraries/delay/nrf_delay.h>
+#include <task.h>
+
+using namespace Pinetime::Drivers;
+
+SC7A20::SC7A20(TwiMaster& twiMaster, uint8_t twiAddress) : AccelerationSensor(twiMaster, twiAddress) {
+}
+
+void SC7A20::Init() {
+  // Reset internal memory
+  uint8_t data = CTRL_REG5_BOOT;
+  Write(CTRL_REG5, &data, 1);
+  vTaskDelay(5);
+  data = 0;
+  Write(CTRL_REG5, &data, 1);
+
+  // Read Chip ID
+  Read(WHO_AM_I, &data, 1);
+  if (data == 17) {
+    deviceType = AccelerationDeviceTypes::SC7A20;
+  } else {
+    deviceType = AccelerationDeviceTypes::Unknown;
+    return;
+  }
+
+  // Configure resolution to be +-2g
+  data = CTRL_REG4_FS_2G;
+  Write(CTRL_REG4, &data, 1);
+
+  // Enable block update, configure 12 bit resolution mode
+  data = CTRL_REG4_BDU | CTRL_REG4_HR;
+  Write(CTRL_REG4, &data, 1);
+
+  // Use FIFO for batch data
+  data = CTRL_REG5_FIFO_EN;
+  Write(CTRL_REG5, &data, 1);
+  data = FIFO_CTRL_REG_FIFO;
+  Write(FIFO_CTRL_REG, &data, 1);
+
+  // Set 200 Hz sample rate, enable all axes
+  data = CTRL_REG1_ODR_200HZ | CTRL_REG1_X_EN | CTRL_REG1_Y_EN | CTRL_REG1_Z_EN;
+  Write(CTRL_REG1, &data, 1);
+
+  isInitialized = true;
+}
+
+AccelerationValues SC7A20::Process() {
+  if (!isInitialized)
+    return {};
+
+  // Read FIFO size, should be about 20 (200 Hz ODR / 10 Hz main loop)
+  uint8_t length = 0;
+  Read(FIFO_SRC_REG, &length, 1);
+  length &= FIFO_SRC_REG_FSS_MASK;
+
+  // Read FIFO samples one by one (full read does not work)
+  for (uint8_t i = 0; i < length; i++) {
+    // Set the most significant bit of the sub-address field for block read
+    Read(0x80 | OUT_X_L, (uint8_t*) &fifo[i], sizeof(int16_t) * 3);
+    // Shift because value is left-justified
+    for (uint8_t j = 0; j < 3; j++)
+      fifo[i][j] >>= (16 - 12);
+    // X and Y axis are swapped because of the way the sensor is mounted in the P8
+    int16_t swap = fifo[i][0];
+    fifo[i][0] = fifo[i][1];
+    fifo[i][1] = swap;
+  }
+
+  // Restart FIFO
+  uint8_t data = FIFO_CTRL_REG_BYPASS;
+  Write(FIFO_CTRL_REG, &data, 1);
+  data = FIFO_CTRL_REG_FIFO;
+  Write(FIFO_CTRL_REG, &data, 1);
+
+  // Compute averages of FIFO
+  int16_t avgs[3] = {0};
+  // 2g range in n bits
+  for (uint8_t i = 0; i < length; i++)
+    for (uint8_t j = 0; j < 3; j++) {
+      avgs[j] += ((fifo[i][j] * 2000) / (1 << (12 - 1)));
+    }
+  for (uint8_t j = 0; j < 3; j++)
+    avgs[j] /= length;
+
+  // Step counting is not implemented
+  return {0, avgs[0], avgs[1], avgs[2], (int16_t*) fifo, length};
+}

src/drivers/SC7A20.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include "drivers/AccelerationSensor.h"
+
+namespace Pinetime {
+  namespace Drivers {
+    class SC7A20 : public AccelerationSensor {
+    public:
+      SC7A20(TwiMaster& twiMaster, uint8_t twiAddress);
+      SC7A20(const SC7A20&) = delete;
+      SC7A20& operator=(const SC7A20&) = delete;
+      SC7A20(SC7A20&&) = delete;
+      SC7A20& operator=(SC7A20&&) = delete;
+
+      void Init();
+      AccelerationValues Process();
+    };
+  }
+}