Diff: source/drivers/MicroBitI2C.cpp

Revision:

1:8aa5cdb4ab67

Child:

4:9fbeeb89de59

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/source/drivers/MicroBitI2C.cpp	Thu Apr 07 01:33:22 2016 +0100
@@ -0,0 +1,134 @@
+/*
+The MIT License (MIT)
+
+Copyright (c) 2016 British Broadcasting Corporation.
+This software is provided by Lancaster University by arrangement with the BBC.
+
+Permission is hereby granted, free of charge, to any person obtaining a
+copy of this software and associated documentation files (the "Software"),
+to deal in the Software without restriction, including without limitation
+the rights to use, copy, modify, merge, publish, distribute, sublicense,
+and/or sell copies of the Software, and to permit persons to whom the
+Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+DEALINGS IN THE SOFTWARE.
+*/
+
+#include "MicroBitConfig.h"
+#include "MicroBitI2C.h"
+#include "ErrorNo.h"
+#include "twi_master.h"
+#include "nrf_delay.h"
+
+/**
+  * Constructor.
+  *
+  * Create an instance of MicroBitI2C for I2C communication.
+  *
+  * @param sda the Pin to be used for SDA
+  *
+  * @param scl the Pin to be used for SCL
+  *
+  * @code
+  * MicroBitI2C i2c(I2C_SDA0, I2C_SCL0);
+  * @endcode
+  *
+  * @note This class presents a wrapped mbed call to capture failed I2C operations caused by a known silicon bug in the nrf51822.
+  * Attempts to automatically reset and restart the I2C hardware if this case is detected.
+  *
+  * For reference see PAN56 in:
+  *
+  * https://www.nordicsemi.com/eng/nordic/Products/nRF51822/PAN-nRF51822/24634
+  *
+  * v2.0 through to v2.4
+  */
+MicroBitI2C::MicroBitI2C(PinName sda, PinName scl) : I2C(sda,scl)
+{
+    this->retries = 0;
+}
+
+/**
+  * Performs a complete read transaction. The bottom bit of the address is forced to 1 to indicate a read.
+  *
+  * @param address 8-bit I2C slave address [ addr | 1 ]
+  *
+  * @param data A pointer to a byte buffer used for storing retrieved data.
+  *
+  * @param length Number of bytes to read.
+  *
+  * @param repeated if true, stop is not sent at the end. Defaults to false.
+  *
+  * @return MICROBIT_OK on success, MICROBIT_I2C_ERROR if an unresolved read failure is detected.
+  */
+int MicroBitI2C::read(int address, char *data, int length, bool repeated)
+{
+    int result = I2C::read(address,data,length,repeated);
+
+    //0 indicates a success, presume failure
+    while(result != 0 && retries < MICROBIT_I2C_MAX_RETRIES)
+    {
+        _i2c.i2c->EVENTS_ERROR = 0;
+        _i2c.i2c->ENABLE       = TWI_ENABLE_ENABLE_Disabled << TWI_ENABLE_ENABLE_Pos;
+        _i2c.i2c->POWER        = 0;
+        nrf_delay_us(5);
+        _i2c.i2c->POWER        = 1;
+        _i2c.i2c->ENABLE       = TWI_ENABLE_ENABLE_Enabled << TWI_ENABLE_ENABLE_Pos;
+        twi_master_init_and_clear();
+        result = I2C::read(address,data,length,repeated);
+        retries++;
+    }
+
+    if(result != 0)
+        return MICROBIT_I2C_ERROR;
+
+    retries = 0;
+    return MICROBIT_OK;
+}
+
+/**
+  * Performs a complete write transaction. The bottom bit of the address is forced to 0 to indicate a write.
+  *
+  * @param address 8-bit I2C slave address [ addr | 0 ]
+  *
+  * @param data A pointer to a byte buffer containing the data to write.
+  *
+  * @param length Number of bytes to write
+  *
+  * @param repeated if true, stop is not sent at the end. Defaults to false.
+  *
+  * @return MICROBIT_OK on success, MICROBIT_I2C_ERROR if an unresolved write failure is detected.
+  */
+int MicroBitI2C::write(int address, const char *data, int length, bool repeated)
+{
+    int result = I2C::write(address,data,length,repeated);
+
+    //0 indicates a success, presume failure
+    while(result != 0 && retries < MICROBIT_I2C_MAX_RETRIES)
+    {
+        _i2c.i2c->EVENTS_ERROR = 0;
+        _i2c.i2c->ENABLE       = TWI_ENABLE_ENABLE_Disabled << TWI_ENABLE_ENABLE_Pos;
+        _i2c.i2c->POWER        = 0;
+        nrf_delay_us(5);
+        _i2c.i2c->POWER        = 1;
+        _i2c.i2c->ENABLE       = TWI_ENABLE_ENABLE_Enabled << TWI_ENABLE_ENABLE_Pos;
+
+        twi_master_init_and_clear();
+        result = I2C::write(address,data,length,repeated);
+        retries++;
+    }
+
+    if(result != 0)
+        return MICROBIT_I2C_ERROR;
+
+    retries = 0;
+    return MICROBIT_OK;
+}