[SPIDriver] Added assertion to prevent multiple simultaneous transactions

src/shared/drivers/spi/SPIBus.h

@@ -99,7 +99,7 @@ public:
      */
     void configure(SPIBusConfig config) override;
 
-private:
+protected:
     /**
      * Writes a single byte on the SPI bus.
      *
@@ -124,7 +124,7 @@ private:
 
     SPI_TypeDef* spi;
 
-    SPIBusConfig config;
+    SPIBusConfig config{};
     bool config_enabled       = true;
     bool first_config_applied = false;
 };

src/shared/drivers/spi/SPIBusInterface.h

@@ -31,6 +31,8 @@
 using miosix::delayUs;
 using miosix::GpioPin;
 
+class SPITransaction;
+
 /**
  * @brief SPI Clock divider.
  * SPI clock frequency will be equal to the SPI peripheral bus clock speed (see
@@ -116,6 +118,7 @@ struct SPIBusConfig
  */
 class SPIBusInterface
 {
+    friend class SPITransaction;
 public:
     SPIBusInterface() {}
 
@@ -198,6 +201,9 @@ public:
      * @return
      */
     virtual void configure(SPIBusConfig config) = 0;
+
+private:
+    bool locked = false; // For use by SPITransaction
 };
 
 /**

src/shared/drivers/spi/SPITransaction.cpp

@@ -23,17 +23,29 @@
 
 #include "SPITransaction.h"
 
+#include <cassert>
+
+SPITransaction::SPITransaction(SPISlave slave)
+    : SPITransaction(slave.bus, slave.cs, slave.config)
+{
+}
+
 SPITransaction::SPITransaction(SPIBusInterface& bus, GpioPin cs,
                                SPIBusConfig config)
     : bus(bus), cs(cs)
 {
+    // Only one SPITransaction may be active at any given time.
+    // Do not store an instance of SPITransaction for a long time! Create one,
+    // use it, and destroy it as soon as you are done operating on the bus!
+    // (just like mutexes)
+#ifdef DEBUG
+    assert(bus.locked == false);
+#endif
+    bus.locked = true;
     bus.configure(config);
 }
 
-SPITransaction::SPITransaction(SPISlave slave)
-    : SPITransaction(slave.bus, slave.cs, slave.config)
-{
-}
+SPITransaction::~SPITransaction() { bus.locked = false; }
 
 void SPITransaction::write(uint8_t cmd)
 {

src/shared/drivers/spi/SPITransaction.h

@@ -41,14 +41,15 @@
  * {
  *     // Transaction begin:
  *     SPITransaction spi(bus, cs, config); // Configures the bus with the
- *                                          // provided parameters
+ *                                          // provided parameters.
  *
  *     spi.write(REG_EX, 0x56); // writes data to REG_EX
  *     uint8_t reg2 = spi.read(REG_EX_2); // reads from REG_EX_2
  *
  *     // ...As many read/writes as you wish...
  *
- *     // transaction end. SPITransaction object is destructed
+ *     // transaction end. SPITransaction object is destructed and the bus is
+ *     // freed for use by someone else
  * }
  */
 class SPITransaction
@@ -72,6 +73,8 @@ public:
      */
     SPITransaction(SPIBusInterface& bus, GpioPin cs, SPIBusConfig config);
 
+    ~SPITransaction();
+
     // Delete copy/move contructors/operators
     SPITransaction(const SPITransaction&) = delete;
     SPITransaction& operator=(const SPITransaction&) = delete;