Merge pull request #8109 from deepikabhavnani/i2c_recovery

Add reset recovery for I2C bus

Author: Cruz Monrreal

components/802.15.4_RF/atmel-rf-driver/source/at24mac.cpp

@@ -29,30 +29,9 @@
 #define EUI64_LEN 8
 #define EUI48_LEN 6
 
-AT24Mac::I2CReset::I2CReset(PinName sda, PinName scl)
-{
-    mbed::DigitalInOut pin_sda(sda, PIN_OUTPUT, PullUp, 1);
-    mbed::DigitalInOut pin_scl(scl, PIN_OUTPUT, PullUp, 0);
-    //generate 9 clocks for worst-case scenario
-    for (int i = 0; i < 10; ++i) {
-        pin_scl = 1;
-        wait_us(5);
-        pin_scl = 0;
-        wait_us(5);
-    }
-    //generate a STOP condition
-    pin_sda = 0;
-    wait_us(5);
-    pin_scl = 1;
-    wait_us(5);
-    pin_sda = 1;
-    wait_us(5);
-}
+using namespace mbed;
 
-/*I2C needs to be reset before constructing the I2C object (in case I2C is stuck)
-  because they use the same pins, therefore i2c_reset has to be before _i2c
-  in the initializer list*/
-AT24Mac::AT24Mac(PinName sda, PinName scl) : i2c_reset(sda, scl), _i2c(sda, scl)
+AT24Mac::AT24Mac(PinName sda, PinName scl) : _i2c(sda , scl)
 {
     // Do nothing
 }

components/802.15.4_RF/atmel-rf-driver/source/at24mac.h

@@ -59,15 +59,6 @@ class AT24Mac {
     int read_eui48(void *buf);
 
 private:
-    /*
-     * Dummy class to allow us to reset I2C before the I2C constructor is called in
-     * the initializer list of AT24Mac's constructor
-     */
-    class I2CReset {
-    public:
-        I2CReset(PinName sda, PinName scl);
-    };
-    I2CReset i2c_reset;
     mbed::I2C _i2c;
 };
 

drivers/I2C.cpp

@@ -13,7 +13,10 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+
 #include "drivers/I2C.h"
+#include "drivers/DigitalInOut.h"
+#include "platform/mbed_wait_api.h"
 
 #if DEVICE_I2C
 
@@ -32,13 +35,15 @@ I2C::I2C(PinName sda, PinName scl) :
 #endif
     _i2c(), _hz(100000)
 {
-    // No lock needed in the constructor
-
+    lock();
     // The init function also set the frequency to 100000
-    i2c_init(&_i2c, sda, scl);
-
+    _sda = sda;
+    _scl = scl;
+    recover(sda, scl);
+    i2c_init(&_i2c, _sda, _scl);
     // Used to avoid unnecessary frequency updates
     _owner = this;
+    unlock();
 }
 
 void I2C::frequency(int hz)
@@ -135,6 +140,52 @@ void I2C::unlock()
     _mutex->unlock();
 }
 
+int I2C::recover(PinName sda, PinName scl)
+{
+    DigitalInOut pin_sda(sda, PIN_INPUT, PullNone, 1);
+    DigitalInOut pin_scl(scl, PIN_INPUT, PullNone, 1);
+
+    // Return as SCL is low and no access to become master.
+    if (pin_scl == 0) {
+        return I2C_ERROR_BUS_BUSY;
+    }
+
+    // Return successfully as SDA and SCL is high
+    if (pin_sda == 1) {
+        return 0;
+    }
+
+    // Send clock pulses, for device to recover 9
+    pin_scl.mode(PullNone);
+    pin_scl.output();
+    for (int count = 0; count < 10; count++) {
+        pin_scl.mode(PullNone);
+        pin_scl = 0;
+        wait_us(5);
+        pin_scl.mode(PullUp);
+        pin_scl = 1;
+        wait_us(5);
+    }
+
+    // Send Stop
+    pin_sda.output();
+    pin_sda = 0;
+    wait_us(5);
+    pin_scl = 1;
+    wait_us(5);
+    pin_sda = 1;
+    wait_us(5);
+
+    pin_sda.input();
+    pin_scl.input();
+    if ((pin_scl == 0) || (pin_sda == 0)) {
+        // Return as SCL is low and no access to become master.
+        return I2C_ERROR_BUS_BUSY;
+    }
+
+    return 0;
+}
+
 #if DEVICE_I2C_ASYNCH
 
 int I2C::transfer(int address, const char *tx_buffer, int tx_length, char *rx_buffer, int rx_length, const event_callback_t &callback, int event, bool repeated)
@@ -169,10 +220,10 @@ void I2C::irq_handler_asynch(void)
     if (_callback && event) {
         _callback.call(event);
     }
+
     if (event) {
         unlock_deep_sleep();
     }
-
 }
 
 void I2C::lock_deep_sleep()

drivers/I2C.h

@@ -17,6 +17,7 @@
 #define MBED_I2C_H
 
 #include "platform/platform.h"
+#include "hal/gpio_api.h"
 
 #if defined (DEVICE_I2C) || defined(DOXYGEN_ONLY)
 
@@ -197,8 +198,24 @@ class I2C : private NonCopyable<I2C> {
 
     i2c_t _i2c;
     static I2C  *_owner;
-    int         _hz;
+    int    _hz;
     static SingletonPtr<PlatformMutex> _mutex;
+    PinName _sda;
+    PinName _scl;
+
+private:
+    /** Recover I2C bus, when stuck with SDA low
+     *  @note : Initialization of I2C bus is required after this API.
+     *
+     *  @param sda I2C data line pin
+     *  @param scl I2C clock line pin
+     *
+     * @returns:
+     *    '0' - Successfully recovered
+     *    'I2C_ERROR_BUS_BUSY' - In case of failure
+     *
+     */
+    int recover(PinName sda, PinName scl);
 };
 
 } // namespace mbed