Diff: UARTService_custom.h

Revision:

29:f7a0e49b826b

Child:

30:66f9750cc44c

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/UARTService_custom.h	Tue Jul 24 00:38:18 2018 +0000
@@ -0,0 +1,206 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2013 ARM Limited
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef __BLE_UART_SERVICE_H__
+#define __BLE_UART_SERVICE_H__
+
+#ifdef YOTTA_CFG_MBED_OS
+#include "mbed-drivers/mbed.h"
+#include "mbed-drivers/Stream.h"
+#else
+#include "mbed.h"
+#include "Stream.h"
+#endif
+
+#include "ble/UUID.h"
+#include "ble/BLE.h"
+
+extern const uint8_t  UARTServiceBaseUUID[UUID::LENGTH_OF_LONG_UUID];
+extern const uint16_t UARTServiceShortUUID;
+extern const uint16_t UARTServiceTXCharacteristicShortUUID;
+extern const uint16_t UARTServiceRXCharacteristicShortUUID;
+
+extern const uint8_t  UARTServiceUUID[UUID::LENGTH_OF_LONG_UUID];
+extern const uint8_t  UARTServiceUUID_reversed[UUID::LENGTH_OF_LONG_UUID];
+
+extern const uint8_t  UARTServiceTXCharacteristicUUID[UUID::LENGTH_OF_LONG_UUID];
+extern const uint8_t  UARTServiceRXCharacteristicUUID[UUID::LENGTH_OF_LONG_UUID];
+
+/**
+* @class UARTService.
+* @brief BLE Service to enable UART over BLE.
+*/
+class UARTService {
+public:
+    /**< Maximum length of data (in bytes) that the UART service module can transmit to the peer. */
+    static const unsigned BLE_UART_SERVICE_MAX_DATA_LEN = (BLE_GATT_MTU_SIZE_DEFAULT - 18);
+
+public:
+
+    /**
+    * @param[ref] ble
+    *               BLE object for the underlying controller.
+    */
+    UARTService(BLE &_ble) :
+        ble(_ble),
+        receiveBuffer(),
+        sendBuffer(),
+        sendBufferIndex(0),
+        numBytesReceived(0),
+        receiveBufferIndex(0),
+        txCharacteristic(UARTServiceTXCharacteristicUUID, receiveBuffer, 1, BLE_UART_SERVICE_MAX_DATA_LEN,
+                         GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE | GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_WRITE_WITHOUT_RESPONSE),
+        rxCharacteristic(UARTServiceRXCharacteristicUUID, sendBuffer, 1, BLE_UART_SERVICE_MAX_DATA_LEN, GattCharacteristic::BLE_GATT_CHAR_PROPERTIES_NOTIFY) {
+        GattCharacteristic *charTable[] = {&txCharacteristic, &rxCharacteristic};
+        GattService         uartService(UARTServiceUUID, charTable, sizeof(charTable) / sizeof(GattCharacteristic *));
+
+        ble.addService(uartService);
+        ble.onDataWritten(this, &UARTService::onDataWritten);
+    }
+
+    /**
+     * Note: TX and RX characteristics are to be interpreted from the viewpoint of the GATT client using this service.
+     */
+    uint16_t getTXCharacteristicHandle() {
+        return txCharacteristic.getValueAttribute().getHandle();
+    }
+
+    /**
+     * Note: TX and RX characteristics are to be interpreted from the viewpoint of the GATT client using this service.
+     */
+    uint16_t getRXCharacteristicHandle() {
+        return rxCharacteristic.getValueAttribute().getHandle();
+    }
+
+    /**
+     * We attempt to collect bytes before pushing them to the UART RX
+     * characteristic; writing to the RX characteristic then generates
+     * notifications for the client. Updates made in quick succession to a
+     * notification-generating characteristic result in data being buffered
+     * in the Bluetooth stack as notifications are sent out. The stack has
+     * its limits for this buffering - typically a small number under 10.
+     * Collecting data into the sendBuffer buffer helps mitigate the rate of
+     * updates. But we shouldn't buffer a large amount of data before updating
+     * the characteristic, otherwise the client needs to turn around and make
+     * a long read request; this is because notifications include only the first
+     * 20 bytes of the updated data.
+     *
+     * @param  buffer The received update.
+     * @param  length Number of characters to be appended.
+     * @return        Number of characters appended to the rxCharacteristic.
+     */
+    size_t write(const void *_buffer, size_t length) {
+        size_t         origLength = length;
+        const uint8_t *buffer     = static_cast<const uint8_t *>(_buffer);
+
+        if (ble.getGapState().connected) {
+            unsigned bufferIndex = 0;
+            while (length) {
+                unsigned bytesRemainingInSendBuffer = BLE_UART_SERVICE_MAX_DATA_LEN - sendBufferIndex;
+                unsigned bytesToCopy                = (length < bytesRemainingInSendBuffer) ? length : bytesRemainingInSendBuffer;
+
+                /* Copy bytes into sendBuffer. */
+                memcpy(&sendBuffer[sendBufferIndex], &buffer[bufferIndex], bytesToCopy);
+                length          -= bytesToCopy;
+                sendBufferIndex += bytesToCopy;
+                bufferIndex     += bytesToCopy;
+
+                /* Have we collected enough? */
+                if ((sendBufferIndex == BLE_UART_SERVICE_MAX_DATA_LEN) ||
+                    // (sendBuffer[sendBufferIndex - 1] == '\r')          ||
+                    (sendBuffer[sendBufferIndex - 1] == '\n')) {
+                    ble.gattServer().write(getRXCharacteristicHandle(), static_cast<const uint8_t *>(sendBuffer), sendBufferIndex);
+                    sendBufferIndex = 0;
+                }
+            }
+        }
+
+        return origLength;
+    }
+
+    /**
+     * Helper function to write out strings.
+     * @param  str The received string.
+     * @return     Number of characters appended to the rxCharacteristic.
+     */
+    size_t writeString(const char *str) {
+        return write(str, strlen(str));
+    }
+
+    /**
+     * Override for Stream::_putc().
+     * @param  c
+     *         This function writes the character c, cast to an unsigned char, to stream.
+     * @return
+     *     The character written as an unsigned char cast to an int or EOF on error.
+     */
+    int _putc(int c) {
+        return (write(&c, 1) == 1) ? 1 : EOF;
+    }
+
+    /**
+     * Override for Stream::_getc().
+     * @return
+     *     The character read.
+     */
+    int _getc() {
+        if (receiveBufferIndex == numBytesReceived) {
+            return EOF;
+        }
+
+        return receiveBuffer[receiveBufferIndex++];
+    }
+
+protected:
+    /**
+     * This callback allows the UART service to receive updates to the
+     * txCharacteristic. The application should forward the call to this
+     * function from the global onDataWritten() callback handler; if that's
+     * not used, this method can be used as a callback directly.
+     */
+    void onDataWritten(const GattWriteCallbackParams *params) {
+        if (params->handle == getTXCharacteristicHandle()) {
+            uint16_t bytesRead = params->len;
+            if (bytesRead <= BLE_UART_SERVICE_MAX_DATA_LEN) {
+                numBytesReceived   = bytesRead;
+                receiveBufferIndex = 0;
+                memcpy(receiveBuffer, params->data, numBytesReceived);
+            }
+        }
+    }
+
+protected:
+    BLE                &ble;
+
+    uint8_t             receiveBuffer[BLE_UART_SERVICE_MAX_DATA_LEN]; /**< The local buffer into which we receive
+                                                                       *   inbound data before forwarding it to the
+                                                                       *   application. */
+
+    uint8_t             sendBuffer[BLE_UART_SERVICE_MAX_DATA_LEN];    /**< The local buffer into which outbound data is
+                                                                       *   accumulated before being pushed to the
+                                                                       *   rxCharacteristic. */
+    uint8_t             sendBufferIndex;
+    uint8_t             numBytesReceived;
+    uint8_t             receiveBufferIndex;
+
+    GattCharacteristic  txCharacteristic; /**< From the point of view of the external client, this is the characteristic
+                                           *   they'd write into in order to communicate with this application. */
+    GattCharacteristic  rxCharacteristic; /**< From the point of view of the external client, this is the characteristic
+                                           *   they'd read from in order to receive the bytes transmitted by this
+                                           *   application. */
+};
+
+#endif /* #ifndef __BLE_UART_SERVICE_H__*/