I2C byte read/write transmition improvement

Author: yarb

targets/TARGET_Cypress/TARGET_PSOC6/cy_i2c_api.c

@@ -119,13 +119,18 @@ void i2c_frequency(i2c_t *obj, int hz)
 
 int i2c_start(i2c_t *obj)
 {
-    // Nothing to do; start/stop is generated by i2c_read/i2c_write
+    /* start/stop is generated by i2c_read/i2c_write */
+    struct i2c_s *i2c = cy_get_i2c(obj);
+    /* Clear state of address */
+    i2c->address_set = false;
     return 0;
 }
 
 int i2c_stop(i2c_t *obj)
 {
     struct i2c_s *i2c = cy_get_i2c(obj);
+    /* Clear state of address */
+    i2c->address_set = false;
     if (i2c->hal_i2c.context.state != CY_SCB_I2C_IDLE) {
         return Cy_SCB_I2C_MasterSendStop(i2c->hal_i2c.base, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context));
     }
@@ -160,19 +165,49 @@ int i2c_byte_read(i2c_t *obj, int last)
 {
     struct i2c_s *i2c = cy_get_i2c(obj);
     uint8_t value;
+
+    /* Slave device address is stored in object by first write operation */
+    if (i2c->address_set) {
+        /* Send slave device address */
+        /* Make sure if I2C transaction direction is 'Read' */
+        if (CY_SCB_I2C_SUCCESS != Cy_SCB_I2C_MasterSendStart(i2c->hal_i2c.base, i2c->address, CY_SCB_I2C_READ_XFER, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context))) {
+            MBED_ERROR(MBED_MAKE_ERROR(MBED_MODULE_DRIVER_I2C, MBED_ERROR_CODE_FAILED_OPERATION), "i2c_send_start");
+        }
+        /* Clear state of address. It is not needed for next operation. */
+        i2c->address_set = false;
+    }
+
+    /* Read next byte */
     if (CY_SCB_I2C_SUCCESS != Cy_SCB_I2C_MasterReadByte(i2c->hal_i2c.base, last != 0 ? CY_SCB_I2C_NAK : CY_SCB_I2C_ACK, &value, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context))) {
-        MBED_ERROR(MBED_MAKE_ERROR(MBED_MODULE_DRIVER_I2C, MBED_ERROR_CODE_FAILED_OPERATION), "i2c_byte_read");
+        MBED_ERROR(MBED_MAKE_ERROR(MBED_MODULE_DRIVER_I2C, MBED_ERROR_CODE_FAILED_OPERATION), "i2c_read_byte");
     }
+
     return value;
 }
 
 int i2c_byte_write(i2c_t *obj, int data)
 {
     struct i2c_s *i2c = cy_get_i2c(obj);
-    // If we have not yet written the address, the first byte being sent is the address.
-    cy_en_scb_i2c_status_t status = i2c->hal_i2c.context.state == CY_SCB_I2C_IDLE
-                                    ? Cy_SCB_I2C_MasterSendStart(i2c->hal_i2c.base, data >> 1, CY_SCB_I2C_WRITE_XFER, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context))
-                                    : Cy_SCB_I2C_MasterWriteByte(i2c->hal_i2c.base, (uint8_t)data, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context));
+    cy_en_scb_i2c_status_t status = CY_SCB_I2C_SUCCESS;
+
+    /* First byte should be address */
+    if (i2c->address_set) {
+        /* Verify if Master is ready for send slave address and send first data byte */
+        /* Make sure that I2C transaction direction is 'Write' */
+        if (i2c->hal_i2c.context.state == CY_SCB_I2C_IDLE) {
+            status = Cy_SCB_I2C_MasterSendStart(i2c->hal_i2c.base, i2c->address, CY_SCB_I2C_WRITE_XFER, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context));
+        }
+
+        if (status == CY_SCB_I2C_SUCCESS) {
+            status = Cy_SCB_I2C_MasterWriteByte(i2c->hal_i2c.base, (uint8_t)data, CY_I2C_DEFAULT_TIMEOUT, &(i2c->hal_i2c.context));
+        }
+    } else {
+        /* Store slave address and remember status for next byte read or write operation */
+        i2c->address = data >> 1;
+        i2c->address_set = true;
+    }
+
+
     switch (status) {
         case CY_SCB_I2C_MASTER_MANUAL_TIMEOUT:
             return 2;

targets/TARGET_Cypress/TARGET_PSOC6/objects.h

@@ -94,6 +94,8 @@ struct i2c_s {
     size_t async_rx_size;
 #endif
     uint8_t slave_event;
+    uint32_t address;
+    bool address_set;
 };
 #endif