Implement write_then_read style API for threadsafe Wire.

Author: aentinger

examples/Threadsafe_Wire_BusIO/Threadsafe_Wire_BusIO.ino

@@ -0,0 +1,78 @@
+ /**************************************************************************************
+ * INCLUDE
+ **************************************************************************************/
+
+#include <Arduino_ThreadsafeIO.h>
+
+/**************************************************************************************
+ * CONSTANTS
+ **************************************************************************************/
+
+static byte constexpr LSM6DSOX_ADDRESS      = 0x6A;
+static byte constexpr LSM6DSOX_WHO_AM_I_REG = 0x0F;
+
+static size_t constexpr NUM_THREADS = 20;
+
+/**************************************************************************************
+ * FUNCTION DECLARATION
+ **************************************************************************************/
+
+byte lsm6dsox_read_reg(byte const reg_addr);
+void lsm6dsox_thread_func();
+
+/**************************************************************************************
+ * GLOBAL VARIABLES
+ **************************************************************************************/
+
+BusDevice lsm6dsox(Wire, LSM6DSOX_ADDRESS);
+
+static char thread_name[NUM_THREADS][32];
+
+/**************************************************************************************
+ * SETUP/LOOP
+ **************************************************************************************/
+
+void setup()
+{
+  Serial.begin(9600);
+  while (!Serial) { }
+
+  /* Fire up some threads all accessing the LSM6DSOX */
+  for(size_t i = 0; i < NUM_THREADS; i++)
+  {
+    snprintf(thread_name[i], sizeof(thread_name[i]), "Thread #%02d", i);
+    rtos::Thread * t = new rtos::Thread(osPriorityNormal, OS_STACK_SIZE, nullptr, thread_name[i]);
+    t->start(lsm6dsox_thread_func);
+  }
+}
+
+void loop()
+{
+
+}
+
+/**************************************************************************************
+ * FUNCTION DEFINITION
+ **************************************************************************************/
+
+byte lsm6dsox_read_reg(byte const reg_addr)
+{
+  byte read_buf = 0;
+  lsm6dsox.wire().write_then_read(&reg_addr, 1, &read_buf, 1);
+  return read_buf;
+}
+
+void lsm6dsox_thread_func()
+{
+  for(;;)
+  {
+    /* Sleep between 5 and 500 ms */
+    rtos::ThisThread::sleep_for(rtos::Kernel::Clock::duration_u32(random(5,500)));
+    /* Try to read some data from the LSM6DSOX. */
+    byte const who_am_i = lsm6dsox_read_reg(LSM6DSOX_WHO_AM_I_REG);
+    /* Print thread id and chip id value to serial. */
+    char msg[64] = {0};
+    snprintf(msg, sizeof(msg), "%s: LSM6DSOX[WHO_AM_I] = 0x%X", rtos::ThisThread::get_name(), who_am_i);
+    Serial.println(msg);
+  }
+}

keywords.txt

@@ -24,6 +24,8 @@ block	KEYWORD2
 unblock	KEYWORD2
 prefix	KEYWORD2
 suffix	KEYWORD2
+wire	KEYWORD2
+write_then_read	KEYWORD2
 
 #######################################
 # Constants (LITERAL1)

src/BusDevice.cpp

@@ -109,3 +109,8 @@ IoResponse BusDevice::transfer(IoRequest & req)
 {
   return _dev->transfer(req);
 }
+
+WireBusDevice & BusDevice::wire()
+{
+  return *reinterpret_cast<WireBusDevice *>(_dev.get());
+}

src/BusDevice.h

@@ -38,6 +38,7 @@ namespace arduino
 }
 
 class BusDevice;
+class WireBusDevice;
 
 /**************************************************************************************
  * CLASS DECLARATION
@@ -79,6 +80,9 @@ class BusDevice
   IoResponse transfer(IoRequest & req);
 
 
+  WireBusDevice & wire();
+
+
 private:
 
   mbed::SharedPtr<BusDeviceBase> _dev;

src/wire/WireBusDevice.h

@@ -50,6 +50,23 @@ class WireBusDevice : public BusDeviceBase
   }
 
 
+  bool write_then_read(const uint8_t * write_buffer, size_t write_len, uint8_t * read_buffer, size_t read_len, bool stop = false)
+  {
+    /* Copy the Wire parameters from the device and modify only those
+     * which can be modified via the parameters of this function.
+     */
+    bool const restart = !stop;
+    WireBusDeviceConfig config(_config.wire(), _config.slave_addr(), restart, _config.stop());
+    /* Fire off the IO request and await its response. */
+    IoRequest req(write_buffer, write_len, read_buffer, read_len);
+    IoResponse rsp = WireDispatcher::instance().dispatch(&req, &config);
+    rsp->wait();
+    /* TODO: Introduce error codes within the IoResponse and evaluate
+     * them here.
+     */
+    return true;
+  }
+
 private:
 
   WireBusDeviceConfig _config;

src/wire/WireDispatcher.h

@@ -43,8 +43,10 @@ class WireDispatcher
   static WireDispatcher & instance();
   static void destroy();
 
+
   IoResponse dispatch(IoRequest * req, WireBusDeviceConfig * config);
 
+
 private:
 
   static WireDispatcher * _p_instance;