NRF52: fix i2c byte read/write implementation

Author: maciejbocianski

targets/TARGET_NORDIC/TARGET_NRF5x/TARGET_NRF52/i2c_api.c

@@ -343,6 +343,106 @@ int i2c_start(i2c_t *obj)
     return 0;
 }
 
+static uint8_t twi_byte_write(NRF_TWI_Type *twi, uint8_t data)
+{
+    uint32_t t0;
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_TXDSENT);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_ERROR);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_BB);
+    (void)nrf_twi_errorsrc_get_and_clear(twi);
+
+    nrf_twi_txd_set(twi, data);
+
+    uint32_t start_us = tick2us * lp_ticker_read();
+    uint8_t ret = 2;
+
+    do {
+        if (nrf_twi_event_check(twi, NRF_TWI_EVENT_TXDSENT)) {
+            nrf_twi_event_clear(twi, NRF_TWI_EVENT_TXDSENT);
+            ret = 1; // ACK received
+            break;
+        }
+        if (nrf_twi_event_check(twi, NRF_TWI_EVENT_ERROR)) {
+            nrf_twi_event_clear(twi, NRF_TWI_EVENT_ERROR);
+            ret = 0; // some error occurred
+            break;
+        }
+    } while (((tick2us * (uint32_t)lp_ticker_read()) - start_us) < MAXIMUM_TIMEOUT_US);
+
+    return ret; // timeout;
+}
+
+static int twi_start_write(NRF_TWI_Type *twi, int address)
+{
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_STOPPED);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_TXDSENT);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_ERROR);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_BB);
+    (void)nrf_twi_errorsrc_get_and_clear(twi);
+
+    nrf_twi_shorts_set(twi, 0);
+
+    nrf_twi_address_set(twi, address >> 1);
+    nrf_twi_task_trigger(twi, NRF_TWI_TASK_RESUME);
+    nrf_twi_task_trigger(twi, NRF_TWI_TASK_STARTTX);
+
+    /* Setup stop watch for timeout. */
+    uint32_t start_us = tick2us * lp_ticker_read();
+    uint32_t now_us = start_us;
+
+    /* Block until timeout or an address error has been detected. */
+    while (((now_us - start_us) < 150) &&
+            !(nrf_twi_event_check(twi, NRF_TWI_EVENT_TXDSENT))) {
+        now_us = tick2us * lp_ticker_read();
+    }
+
+    /* Check error register and update return value if an address NACK was detected. */
+    uint32_t error = nrf_twi_errorsrc_get_and_clear(twi);
+
+    if (error & NRF_TWI_ERROR_ADDRESS_NACK) {
+        return 0; // set NACK
+    } else if (now_us - start_us >= DEFAULT_TIMEOUT_US) {
+        return 2; // set timeout
+    }
+
+    return 1; // ACK
+}
+
+static int twi_start_read(NRF_TWI_Type *twi, int address)
+{
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_STOPPED);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_RXDREADY);
+    nrf_twi_event_clear(twi, NRF_TWI_EVENT_ERROR);
+    (void)nrf_twi_errorsrc_get_and_clear(twi);
+
+    nrf_twi_shorts_set(twi, NRF_TWI_SHORT_BB_SUSPEND_MASK);
+
+    nrf_twi_address_set(twi, address >> 1);
+    nrf_twi_task_trigger(twi, NRF_TWI_TASK_RESUME);
+    nrf_twi_task_trigger(twi, NRF_TWI_TASK_STARTRX);
+
+        /* Setup stop watch for timeout. */
+    uint32_t start_us = tick2us * lp_ticker_read();
+    uint32_t now_us = start_us;
+
+    /* Block until timeout or an address error has been detected. */
+    while (((now_us - start_us) < 150) &&
+            !(nrf_twi_event_check(twi, NRF_TWI_EVENT_TXDSENT))) {
+        now_us = tick2us * lp_ticker_read();
+    }
+
+    /* Check error register and update return value if an address NACK was detected. */
+    uint32_t error = nrf_twi_errorsrc_get_and_clear(twi);
+
+    if (error & NRF_TWI_ERROR_ADDRESS_NACK) {
+        return 0; // set NACK
+    } else if (now_us - start_us >= DEFAULT_TIMEOUT_US) {
+        return 2; // set timeout
+    }
+
+    return 1; // ACK
+}
+
 /** Write one byte
  *
  *  @param obj The I2C object
@@ -359,72 +459,27 @@ int i2c_byte_write(i2c_t *obj, int data)
     struct i2c_s *config = obj;
 #endif
 
-    int instance = config->instance;
+    NRF_TWI_Type *p_twi = nordic_nrf5_twi_register[config->instance];
     int result = 1; // default to ACK
 
-    /* Check if this is the first byte to be transferred. If it is, then send start signal and address. */
     if (config->state == NORDIC_TWI_STATE_START) {
         config->state = NORDIC_TWI_STATE_BUSY;
 
-        /* Beginning of new transaction, configure peripheral if necessary. */
+        config->update = true;
         i2c_configure_twi_instance(obj);
 
-        /* Set I2C device address. NOTE: due to hardware limitations only 7-bit addresses are supported. */
-        nrf_twi_address_set(nordic_nrf5_twi_register[instance], data >> 1);
-
-        /* If read bit is set, trigger read task otherwise trigger write task. */
         if (data & I2C_READ_BIT) {
-            /* For timing reasons, reading bytes requires shorts to suspend peripheral after each byte. */
-            nrf_twi_shorts_set(nordic_nrf5_twi_register[instance], NRF_TWI_SHORT_BB_SUSPEND_MASK);
-            nrf_twi_task_trigger(nordic_nrf5_twi_register[instance], NRF_TWI_TASK_STARTRX);
-        } else {
-            /* Reset shorts register. */
-            nrf_twi_shorts_set(nordic_nrf5_twi_register[instance], 0);
-            nrf_twi_task_trigger(nordic_nrf5_twi_register[instance], NRF_TWI_TASK_STARTTX);
-        }
-
-        /* Setup stop watch for timeout. */
-        uint32_t start_us = tick2us * lp_ticker_read();
-        uint32_t now_us = start_us;
-
-        /* Block until timeout or an address error has been detected. */
-        while (((now_us - start_us) < DEFAULT_TIMEOUT_US) &&
-               !(nrf_twi_event_check(nordic_nrf5_twi_register[instance], NRF_TWI_EVENT_ERROR))) {
-            now_us = tick2us * lp_ticker_read();
-        }
-
-        /* Check error register and update return value if an address NACK was detected. */
-        uint32_t error = nrf_twi_errorsrc_get_and_clear(nordic_nrf5_twi_register[instance]);
-
-        if (error & NRF_TWI_ERROR_ADDRESS_NACK) {
-            result = 0; // set NACK
+            return twi_start_read(p_twi, data);
         } else {
-            /* Normal write. Send next byte after clearing event flag. */
-            nrf_twi_event_clear(nordic_nrf5_twi_register[instance], NRF_TWI_EVENT_TXDSENT);
-            nrf_twi_txd_set(nordic_nrf5_twi_register[instance], data);
-
-            /* Setup stop watch for timeout. */
-            uint32_t start_us = tick2us * lp_ticker_read();
-            uint32_t now_us = start_us;
-
-            /* Block until timeout or the byte has been sent. */
-            while (((now_us - start_us) < MAXIMUM_TIMEOUT_US) &&
-                !(nrf_twi_event_check(nordic_nrf5_twi_register[instance], NRF_TWI_EVENT_TXDSENT))) {
-                now_us = tick2us * lp_ticker_read();
-            }
-
-            /* Check the error code to see if the byte was acknowledged. */
-            uint32_t error = nrf_twi_errorsrc_get_and_clear(nordic_nrf5_twi_register[instance]);
-
-            if (error & NRF_TWI_ERROR_DATA_NACK) {
-                result = 0; // set NACK
-            } else if (now_us - start_us >= MAXIMUM_TIMEOUT_US) {
-                result = 2; // set timeout
-            }
+            return twi_start_write(p_twi, data);
         }
+    } else {
+        nrf_twi_task_trigger(p_twi, NRF_TWI_TASK_RESUME);
+        // 0 - TWI signaled error (NAK is the only possibility here)
+        // 1 - ACK received
+        // 2 - timeout (clock stretched for too long?)
+        return twi_byte_write(p_twi, (uint8_t)data);
     }
-
-    return result;
 }
 
 /** Read one byte