JIRA-560 I2C Bus Scan

using read instead of write to avoid sending the extra byte when scaning I2C bus

Author: Xie,Qi

cores/arduino/i2c.c

@@ -28,6 +28,7 @@
 static volatile uint8_t i2c_tx_complete;
 static volatile uint8_t i2c_rx_complete;
 static volatile uint8_t i2c_err_detect;
+static volatile uint32_t i2c_err_source;
 
 static volatile uint8_t i2c_slave = 0;
 
@@ -44,13 +45,25 @@ static void ss_i2c_tx(uint32_t dev_id)
 static void ss_i2c_err(uint32_t dev_id)
 {
 	i2c_err_detect = 1;
+	i2c_err_source = dev_id;
 }
 
 static int wait_rx_or_err(bool no_stop){
 	uint64_t timeout = TIMEOUT_MS;
 	while(timeout--) {
 		if (i2c_err_detect) {
-			return I2C_ERROR;
+			if (i2c_err_source & I2C_ABRT_7B_ADDR_NOACK )
+			{
+				return I2C_ERROR_ADDRESS_NOACK; // NACK on transmit of address
+			}
+			else if (i2c_err_source & I2C_ABRT_TXDATA_NOACK )
+			{
+				return I2C_ERROR_DATA_NOACK; // NACK on transmit of data
+			}
+			else
+			{
+				return I2C_ERROR_OTHER; // other error
+			}
 		}
 		if (!no_stop) {
 			if (i2c_rx_complete) {
@@ -69,7 +82,18 @@ static int wait_tx_or_err(bool no_stop){
 	uint64_t timeout = TIMEOUT_MS;
 	while(timeout--) {
 		if (i2c_err_detect) {
-			return I2C_ERROR;
+			if (i2c_err_source & I2C_ABRT_7B_ADDR_NOACK )
+			{
+				return I2C_ERROR_ADDRESS_NOACK; // NACK on transmit of address
+			}
+			else if (i2c_err_source & I2C_ABRT_TXDATA_NOACK )
+			{
+				return I2C_ERROR_DATA_NOACK; // NACK on transmit of data
+			}
+			else
+			{
+				return I2C_ERROR_OTHER; // other error
+			}
 		}
 		if (!no_stop) {
 			if (i2c_tx_complete) {
@@ -86,16 +110,17 @@ static int wait_tx_or_err(bool no_stop){
 
 static int wait_dev_ready(I2C_CONTROLLER controller_id, bool no_stop){
 	uint64_t timeout = TIMEOUT_MS;
+	int ret = 0;
 	while(timeout--) {
-		int ret = ss_i2c_status(controller_id, no_stop);
+		ret = ss_i2c_status(controller_id, no_stop);
 		if (ret == I2C_OK) {
 			return I2C_OK;
 		}
 		if (ret == I2C_BUSY) {
 			delay(1);
 		}
 	}
-	return I2C_TIMEOUT;
+	return I2C_TIMEOUT - ret;
 }
 
 
@@ -122,6 +147,7 @@ int i2c_openadapter(void)
 	i2c_tx_complete = 0;
 	i2c_rx_complete = 0;
 	i2c_err_detect = 0;
+	i2c_err_source = 0;
 
 	ss_i2c_set_config(I2C_SENSING_0, &i2c_cfg);
 	ss_i2c_clock_enable(I2C_SENSING_0);
@@ -142,6 +168,7 @@ int i2c_writebytes(uint8_t *bytes, uint8_t length, bool no_stop)
 
 	i2c_tx_complete = 0;
 	i2c_err_detect = 0;
+	i2c_err_source = 0;
 	ss_i2c_transfer(I2C_SENSING_0, bytes, length, 0, 0, i2c_slave, no_stop);
 	ret = wait_tx_or_err(no_stop);
 	if (ret)
@@ -158,6 +185,7 @@ int i2c_readbytes(uint8_t *buf, int length, bool no_stop)
 
 	i2c_rx_complete = 0;
 	i2c_err_detect = 0;
+	i2c_err_source = 0;
 	ss_i2c_transfer(I2C_SENSING_0, 0, 0, buf, length, i2c_slave, no_stop);
 	ret = wait_rx_or_err(no_stop);
 	if (ret)

cores/arduino/i2c.h

@@ -28,8 +28,14 @@ extern "C"{
 #endif
 
 #define I2C_OK       0
-#define I2C_TIMEOUT -1
-#define I2C_ERROR   -2
+#define I2C_TIMEOUT -10
+#define I2C_ERROR   -11
+#define I2C_ERROR_ADDRESS_NOACK (-2)
+#define I2C_ERROR_DATA_NOACK    (-3)
+#define I2C_ERROR_OTHER         (-4)
+
+#define I2C_ABRT_7B_ADDR_NOACK  (1 << 0)
+#define I2C_ABRT_TXDATA_NOACK   (1 << 3)
 
 int i2c_openadapter(void);
 void i2c_setslave(uint8_t addr);

libraries/Wire/examples/bus_scan/bus_scan.ino

@@ -0,0 +1,63 @@
+/*
+  Sketch: I2CBusScan.ino
+
+  This sketch demonstrates the usage of the Curie Wire Library.
+  It scan the I2C bus to find slave devices
+
+  You can see the found I2C slave device shown in serial output
+  with the following message:
+     address:xxx  found
+
+  created by Intel
+  Modified 18 May 2016
+
+  This example code is in the public domain.
+*/
+
+
+#include <Wire.h>
+
+byte startAddress = 1; // skip reserved address from 0 to 7
+byte endAddress   = 127;
+
+void I2CBusScan(byte startAddress, byte endAddress)
+{
+  byte retval;
+  char temp[64];
+  for( byte address = startAddress; address <= endAddress; address++ ) {
+    Wire.beginTransmission(address);
+    retval = Wire.endTransmission();
+    sprintf(temp, "address: %-4d%-5s", address, (retval == 0 || retval == 3) ? "found" : "");
+    Serial.print(temp);
+    Serial.print((address % 4) ? '\t' : '\n');
+  }
+}
+
+void setup()
+{
+  // Initialize pin 13 as an output - onboard LED.
+  pinMode(13, OUTPUT);
+
+  // join i2c bus (address optional for master)
+  Wire.begin();
+
+  Serial.begin(115200);
+}
+
+boolean toggle = false;          // state of the LED
+void loop()
+{
+  toggle = !toggle;
+  digitalWrite(13, toggle);
+  delay(5000);
+
+  Serial.print("Start I2C Bus Scan from ");
+  Serial.print(startAddress);
+  Serial.print(" to ");
+  Serial.print(endAddress);
+  Serial.println(".....");
+
+  I2CBusScan( startAddress, endAddress);
+
+  Serial.println("\ndone");
+}

libraries/Wire/src/Wire.cpp

@@ -107,22 +107,20 @@ uint8_t TwoWire::endTransmission(uint8_t sendStop)
 {
 	int err;
 		// transmit buffer (blocking)
-		if (txBufferLength >= 1) {
-			err = i2c_writebytes(txBuffer, txBufferLength, !sendStop);
-		} else {
-            //Workaround: I2C bus scan is currently implemented by sending an extra byte of value 0
-            txBuffer[0] = 0;
-            err = i2c_writebytes(txBuffer, 1, !sendStop);
-		}
-		// empty buffer
-		txBufferLength = 0;
-		if (err < 0) {
-			return 2; // NACK on transmit of address
-			/* NOTE: This implementation currently does not distinguish
-			 * between NACK on transmit of adddress or data, or other errors
-			 */
-		}
-		return 0; // success
+	if (txBufferLength >= 1) {
+		err = i2c_writebytes(txBuffer, txBufferLength, !sendStop);
+	} else {
+		uint8_t temp = 0;
+		// Workaround: I2C bus scan is currently implemented by reading,
+		// so set the read length to 0 to inform the lower I2C driver that we are doing bus scan
+		err = i2c_readbytes(&temp, 0, 0);
+	}
+	// empty buffer
+	txBufferLength = 0;
+	if (err < 0) {
+		return -err;
+	}
+	return 0; // success
 }
 
 //	This provides backwards compatibility with the original

system/libarc32_arduino101/drivers/i2c_priv.h

@@ -132,6 +132,7 @@ typedef struct i2c_info {
     uint32_t        rx_tx_len;      // tx_len + rx_len
     uint8_t         *i2c_write_buff;
     uint8_t         *i2c_read_buff;
+    uint8_t         restart;
 
     /* Callbacks */
     IO_CB_FUNC      tx_cb;

system/libarc32_arduino101/drivers/ss_dw_i2c.c

@@ -127,6 +127,11 @@ void i2c_fill_fifo(i2c_info_pt dev, bool no_stop)
             { // last dummy byte to write
                 if(! no_stop)
                     data |= I2C_STOP_CMD;
+                if(dev->restart)
+                {
+                    data |= I2C_RESTART_CMD;
+                    dev->restart = false;
+                }
             }
          }
         REG_WRITE( I2C_DATA_CMD, data );
@@ -166,6 +171,7 @@ void i2c_mst_err_ISR_proc(i2c_info_pt dev)
     if( status & R_TX_ABRT  )
     {
         dev->status_code = status;
+        dev->cb_err_data = REG_READ( I2C_TX_ABRT_SOURCE );
         REG_WRITE( I2C_CLR_INTR, R_TX_ABRT );
         REG_WRITE( I2C_INTR_MASK, I2C_INT_DSB );
         dev->state = I2C_STATE_READY;
@@ -177,6 +183,7 @@ void i2c_mst_err_ISR_proc(i2c_info_pt dev)
     if( (status & R_TX_OVER)||(status & R_RX_OVER) )
     {
         dev->status_code = status;
+        dev->cb_err_data = REG_READ( I2C_TX_ABRT_SOURCE );
         REG_WRITE( I2C_CLR_INTR, R_TX_OVER|R_RX_OVER );
         REG_WRITE( I2C_INTR_MASK, I2C_INT_DSB );
         dev->state = I2C_STATE_READY;

system/libarc32_arduino101/drivers/ss_i2c_iface.c

@@ -188,6 +188,7 @@ DRIVER_API_RC ss_i2c_set_config(I2C_CONTROLLER controller_id, i2c_cfg_data_t *co
     /* do some check here to see if this controller is accessible form this core */
 
     dev = &i2c_master_devs[SS_CTRL_ID(controller_id)];
+    dev->restart = false;
     i2c_handles[SS_CTRL_ID(controller_id)] = dev;
 
     /* enable clock to controller to allow reg writes */
@@ -346,6 +347,12 @@ DRIVER_API_RC ss_i2c_transfer(I2C_CONTROLLER controller_id, uint8_t *data_write,
         return DRV_RC_FAIL;
     }
 
+    if ((data_read_len == 0) && (data_write_len == 0))
+    {
+        //Workaround: we know that we are doing I2C bus scan.
+        data_read_len = 1; 
+        dev->restart = true;
+    }
     /* Protect registers using lock and unlock of interruptions */
     saved = interrupt_lock();