By locking each IO expander transaction race conditions due to shared access to Wire can be eliminated.

src/Braccio++.cpp

@@ -24,7 +24,7 @@ BraccioClass::BraccioClass()
 : serial485{Serial1, 0, 7, 8} /* TX, DE, RE */
 , servos{serial485}
 , PD_UFP{PD_LOG_LEVEL_VERBOSE}
-, _expander{TCA6424A_ADDRESS_ADDR_HIGH}
+, _expander{TCA6424A_ADDRESS_ADDR_HIGH, i2c_mutex}
 , _is_ping_allowed{true}
 , _is_motor_connected{false}
 , _motors_connected_mtx{}
@@ -72,7 +72,7 @@ bool BraccioClass::begin(voidFuncPtr custom_menu)
   _bl.turnOn();
 
   SPI.begin();
-  i2c_mutex.lock();
+
   int ret = _expander.testConnection();
 
   if (ret == false) {
@@ -99,7 +99,6 @@ bool BraccioClass::begin(voidFuncPtr custom_menu)
   for (int id = SmartServoClass::MIN_MOTOR_ID; id <= SmartServoClass::MAX_MOTOR_ID; id++) {
     setRed(id);
   }
-  i2c_mutex.unlock();
 
   pinMode(BTN_LEFT, INPUT_PULLUP);
   pinMode(BTN_RIGHT, INPUT_PULLUP);
@@ -360,14 +359,12 @@ void BraccioClass::motorConnectedThreadFunc()
         setMotorConnectionStatus(id, is_connected);
       }
 
-      i2c_mutex.lock();
       for (int id = SmartServoClass::MIN_MOTOR_ID; id <= SmartServoClass::MAX_MOTOR_ID; id++) {
         if (connected(id))
           setGreen(id);
         else
           setRed(id);
       }
-      i2c_mutex.unlock();
     }
     delay(1000);
   }

src/lib/ioexpander/TCA6424A.cpp

@@ -35,7 +35,9 @@ THE SOFTWARE.
 /** Default constructor, uses default I2C address.
  * @see TCA6424A_DEFAULT_ADDRESS
  */
-TCA6424A::TCA6424A() {
+TCA6424A::TCA6424A(rtos::Mutex & wire_mtx)
+: _wire_mtx{wire_mtx}
+{
     devAddr = TCA6424A_DEFAULT_ADDRESS;
 }
 
@@ -45,8 +47,11 @@ TCA6424A::TCA6424A() {
  * @see TCA6424A_ADDRESS_ADDR_LOW
  * @see TCA6424A_ADDRESS_ADDR_HIGH
  */
-TCA6424A::TCA6424A(uint8_t address) {
-    devAddr = address;
+TCA6424A::TCA6424A(uint8_t address, rtos::Mutex & wire_mtx)
+: devAddr{address}
+, _wire_mtx{wire_mtx}
+{
+
 }
 
 /** Power on and prepare for general usage.
@@ -62,6 +67,7 @@ void TCA6424A::initialize() {
  * @return True if connection is valid, false otherwise
  */
 bool TCA6424A::testConnection() {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     return I2Cdev::readBytes(devAddr, TCA6424A_RA_INPUT0, 3, buffer) == 3;
 }
 
@@ -71,6 +77,7 @@ bool TCA6424A::testConnection() {
  * @return Pin logic level (0 or 1)
  */
 bool TCA6424A::readPin(uint16_t pin) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBit(devAddr, TCA6424A_RA_INPUT0 + (pin / 8), pin % 8, buffer);
     return buffer[0];
 }
@@ -79,6 +86,7 @@ bool TCA6424A::readPin(uint16_t pin) {
  * @return 8 pins' logic levels (0 or 1 for each pin)
  */
 uint8_t TCA6424A::readBank(uint8_t bank) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readByte(devAddr, TCA6424A_RA_INPUT0 + bank, buffer);
     return buffer[0];
 }
@@ -87,6 +95,7 @@ uint8_t TCA6424A::readBank(uint8_t bank) {
  * @param banks Container for all bank's pin values (P00-P27)
  */
 void TCA6424A::readAll(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_INPUT0, 3, banks);
 }
 /** Get all pin logic levels from all banks.
@@ -96,6 +105,7 @@ void TCA6424A::readAll(uint8_t *banks) {
  * @param bank2 Container for Bank 2's pin values (P20-P27)
  */
 void TCA6424A::readAll(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_INPUT0, 3, buffer);
     *bank0 = buffer[0];
     *bank1 = buffer[1];
@@ -110,6 +120,7 @@ void TCA6424A::readAll(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
  * @return Pin output setting (0 or 1)
  */
 bool TCA6424A::getPinOutputLevel(uint16_t pin) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBit(devAddr, TCA6424A_RA_OUTPUT0 + (pin / 8), pin % 8, buffer);
     return buffer[0];
 }
@@ -120,6 +131,7 @@ bool TCA6424A::getPinOutputLevel(uint16_t pin) {
  * @return 8 pins' output settings (0 or 1 for each pin)
  */
 uint8_t TCA6424A::getBankOutputLevel(uint8_t bank) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readByte(devAddr, TCA6424A_RA_OUTPUT0 + bank, buffer);
     return buffer[0];
 }
@@ -128,6 +140,7 @@ uint8_t TCA6424A::getBankOutputLevel(uint8_t bank) {
  * @param banks Container for all bank's pin values (P00-P27)
  */
 void TCA6424A::getAllOutputLevel(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_OUTPUT0, 3, banks);
 }
 /** Get all pin output settings from all banks.
@@ -139,6 +152,7 @@ void TCA6424A::getAllOutputLevel(uint8_t *banks) {
  * @param bank2 Container for Bank 2's pin values (P20-P27)
  */
 void TCA6424A::getAllOutputLevel(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_OUTPUT0, 3, buffer);
     *bank0 = buffer[0];
     *bank1 = buffer[1];
@@ -149,19 +163,22 @@ void TCA6424A::getAllOutputLevel(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2)
  * @param value New pin output logic level (0 or 1)
  */
 void TCA6424A::writePin(uint16_t pin, bool value) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeBit(devAddr, TCA6424A_RA_OUTPUT0 + (pin / 8), pin % 8, value);
 }
 /** Set all OUTPUT pins' logic levels in one bank.
  * @param bank Which bank to write (0/1/2 for P0*, P1*, P2* respectively)
  * @param value New pins' output logic level (0 or 1 for each pin)
  */
 void TCA6424A::writeBank(uint8_t bank, uint8_t value) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeByte(devAddr, TCA6424A_RA_OUTPUT0 + bank, value);
 }
 /** Set all OUTPUT pins' logic levels in all banks.
  * @param banks All pins' new logic values (P00-P27) in 3-byte array
  */
 void TCA6424A::writeAll(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeBytes(devAddr, TCA6424A_RA_OUTPUT0 | TCA6424A_AUTO_INCREMENT, 3, banks);
 }
 /** Set all OUTPUT pins' logic levels in all banks.
@@ -170,6 +187,7 @@ void TCA6424A::writeAll(uint8_t *banks) {
  * @param bank2 Bank 2's new logic values (P20-P27)
  */
 void TCA6424A::writeAll(uint8_t bank0, uint8_t bank1, uint8_t bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     buffer[0] = bank0;
     buffer[1] = bank1;
     buffer[2] = bank2;
@@ -182,6 +200,7 @@ void TCA6424A::writeAll(uint8_t bank0, uint8_t bank1, uint8_t bank2) {
  * @return Pin polarity setting (0 or 1)
  */
 bool TCA6424A::getPinPolarity(uint16_t pin) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBit(devAddr, TCA6424A_RA_POLARITY0 + (pin / 8), pin % 8, buffer);
     return buffer[0];
 }
@@ -190,6 +209,7 @@ bool TCA6424A::getPinPolarity(uint16_t pin) {
  * @return 8 pins' polarity settings (0 or 1 for each pin)
  */
 uint8_t TCA6424A::getBankPolarity(uint8_t bank) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readByte(devAddr, TCA6424A_RA_POLARITY0 + bank, buffer);
     return buffer[0];
 }
@@ -198,6 +218,7 @@ uint8_t TCA6424A::getBankPolarity(uint8_t bank) {
  * @param banks Container for all bank's pin values (P00-P27)
  */
 void TCA6424A::getAllPolarity(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_POLARITY0, 3, banks);
 }
 /** Get all pin polarity (normal/inverted) settings from all banks.
@@ -207,6 +228,7 @@ void TCA6424A::getAllPolarity(uint8_t *banks) {
  * @param bank2 Container for Bank 2's pin values (P20-P27)
  */
 void TCA6424A::getAllPolarity(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_POLARITY0, 3, buffer);
     *bank0 = buffer[0];
     *bank1 = buffer[1];
@@ -217,19 +239,22 @@ void TCA6424A::getAllPolarity(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
  * @param polarity New pin polarity setting (0 or 1)
  */
 void TCA6424A::setPinPolarity(uint16_t pin, bool polarity) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeBit(devAddr, TCA6424A_RA_POLARITY0 + (pin / 8), pin % 8, polarity);
 }
 /** Set all pin polarity (normal/inverted) settings in one bank.
  * @param bank Which bank to write (0/1/2 for P0*, P1*, P2* respectively)
  * @return New pins' polarity settings (0 or 1 for each pin)
  */
 void TCA6424A::setBankPolarity(uint8_t bank, uint8_t polarity) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeByte(devAddr, TCA6424A_RA_POLARITY0 + bank, polarity);
 }
 /** Set all pin polarity (normal/inverted) settings in all banks.
  * @param banks All pins' new logic values (P00-P27) in 3-byte array
  */
 void TCA6424A::setAllPolarity(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeBytes(devAddr, TCA6424A_RA_POLARITY0 | TCA6424A_AUTO_INCREMENT, 3, banks);
 }
 /** Set all pin polarity (normal/inverted) settings in all banks.
@@ -238,6 +263,7 @@ void TCA6424A::setAllPolarity(uint8_t *banks) {
  * @param bank2 Bank 2's new polarity values (P20-P27)
  */
 void TCA6424A::setAllPolarity(uint8_t bank0, uint8_t bank1, uint8_t bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     buffer[0] = bank0;
     buffer[1] = bank1;
     buffer[2] = bank2;
@@ -250,6 +276,7 @@ void TCA6424A::setAllPolarity(uint8_t bank0, uint8_t bank1, uint8_t bank2) {
  * @return Pin direction setting (0 or 1)
  */
 bool TCA6424A::getPinDirection(uint16_t pin) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBit(devAddr, TCA6424A_RA_CONFIG0 + (pin / 8), pin % 8, buffer);
     return buffer[0];
 }
@@ -258,6 +285,7 @@ bool TCA6424A::getPinDirection(uint16_t pin) {
  * @return 8 pins' direction settings (0 or 1 for each pin)
  */
 uint8_t TCA6424A::getBankDirection(uint8_t bank) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readByte(devAddr, TCA6424A_RA_CONFIG0 + bank, buffer);
     return buffer[0];
 }
@@ -266,6 +294,7 @@ uint8_t TCA6424A::getBankDirection(uint8_t bank) {
  * @param banks Container for all bank's pin values (P00-P27)
  */
 void TCA6424A::getAllDirection(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_CONFIG0, 3, banks);
 }
 /** Get all pin direction (I/O) settings from all banks.
@@ -275,6 +304,7 @@ void TCA6424A::getAllDirection(uint8_t *banks) {
  * @param bank2 Container for Bank 2's pin values (P20-P27)
  */
 void TCA6424A::getAllDirection(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::readBytes(devAddr, TCA6424A_RA_CONFIG0, 3, buffer);
     *bank0 = buffer[0];
     *bank1 = buffer[1];
@@ -285,19 +315,22 @@ void TCA6424A::getAllDirection(uint8_t *bank0, uint8_t *bank1, uint8_t *bank2) {
  * @param direction Pin direction setting (0 or 1)
  */
 void TCA6424A::setPinDirection(uint16_t pin, bool direction) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeBit(devAddr, TCA6424A_RA_CONFIG0 + (pin / 8), pin % 8, direction);
 }
 /** Set all pin direction (I/O) settings in one bank.
  * @param bank Which bank to read (0/1/2 for P0*, P1*, P2* respectively)
  * @param direction New pins' direction settings (0 or 1 for each pin)
  */
 void TCA6424A::setBankDirection(uint8_t bank, uint8_t direction) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeByte(devAddr, TCA6424A_RA_CONFIG0 + bank, direction);
 }
 /** Set all pin direction (I/O) settings in all banks.
  * @param banks All pins' new direction values (P00-P27) in 3-byte array
  */
 void TCA6424A::setAllDirection(uint8_t *banks) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     I2Cdev::writeBytes(devAddr, TCA6424A_RA_CONFIG0 | TCA6424A_AUTO_INCREMENT, 3, banks);
 }
 /** Set all pin direction (I/O) settings in all banks.
@@ -306,6 +339,7 @@ void TCA6424A::setAllDirection(uint8_t *banks) {
  * @param bank2 Bank 2's new direction values (P20-P27)
  */
 void TCA6424A::setAllDirection(uint8_t bank0, uint8_t bank1, uint8_t bank2) {
+    mbed::ScopedLock<rtos::Mutex> lock(_wire_mtx);
     buffer[0] = bank0;
     buffer[1] = bank1;
     buffer[2] = bank2;

src/lib/ioexpander/TCA6424A.h

@@ -90,8 +90,8 @@ THE SOFTWARE.
 
 class TCA6424A {
     public:
-        TCA6424A();
-        TCA6424A(uint8_t address);
+        TCA6424A(rtos::Mutex & wire_mtx);
+        TCA6424A(uint8_t address, rtos::Mutex & wire_mtx);
 
         void initialize();
         bool testConnection();
@@ -133,6 +133,7 @@ class TCA6424A {
         void setAllDirection(uint8_t bank0, uint8_t bank1, uint8_t bank2);
 
     private:
+        rtos::Mutex & _wire_mtx;
         uint8_t devAddr;
         uint8_t buffer[3];
 };