Diff: BLE_API/services/UARTService.h

Revision:

0:76dfa9657d9d

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/BLE_API/services/UARTService.h	Wed Nov 12 02:40:34 2014 +0000
@@ -0,0 +1,203 @@
+/* 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__
+
+#include "Stream.h"
+
+#include "UUID.h"
+#include "BLEDevice.h"
+
+extern const uint8_t UARTServiceBaseUUID[LENGTH_OF_LONG_UUID];
+extern const uint16_t UARTServiceShortUUID;
+extern const uint16_t UARTServiceTXCharacteristicShortUUID;
+extern const uint16_t UARTServiceRXCharacteristicShortUUID;
+
+extern const uint8_t UARTServiceUUID[LENGTH_OF_LONG_UUID];
+extern const uint8_t UARTServiceUUID_reversed[LENGTH_OF_LONG_UUID];
+
+extern const uint8_t UARTServiceTXCharacteristicUUID[LENGTH_OF_LONG_UUID];
+extern const uint8_t UARTServiceRXCharacteristicUUID[LENGTH_OF_LONG_UUID];
+
+class UARTService : public Stream {
+public:
+    /**< Maximum length of data (in bytes) that can be transmitted by the UART service module to the peer. */
+    static const unsigned GATT_MTU_SIZE_DEFAULT = 23;
+    static const unsigned BLE_UART_SERVICE_MAX_DATA_LEN = (GATT_MTU_SIZE_DEFAULT - 3);
+
+public:
+    UARTService(BLEDevice &_ble) :
+        Stream("blueart"),
+        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();
+    }
+
+    /**
+     * Following a call to this function, all writes to stdout (such as from
+     * printf) get redirected to the outbound characteristic of this service.
+     * This might be very useful when wanting to receive debug messages over BLE.
+     *
+     * @Note: debug messages originating from printf() like calls are buffered
+     * before being sent out. A '\n' in the printf() triggers the buffer update
+     * to the underlying characteristic.
+     *
+     * @Note: long messages need to be chopped up into 20-byte updates so that
+     * they flow out completely with notifications. The receiver should be
+     * prepared to stitch these messages back.
+     */
+    void retargetStdout() {
+        freopen("/blueart", "w", stdout);
+    }
+
+    /**
+     * 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; or if that's
+     * not used, this method can be used as a callback directly.
+     */
+    virtual void onDataWritten(const GattCharacteristicWriteCBParams *params) {
+        if (params->charHandle == getTXCharacteristicHandle()) {
+            uint16_t bytesRead = params->len;
+            if (bytesRead <= BLE_UART_SERVICE_MAX_DATA_LEN) {
+                numBytesReceived   = bytesRead;
+                receiveBufferIndex = 0;
+                memcpy(receiveBuffer, params->data, numBytesReceived);
+            }
+        }
+    }
+
+protected:
+    /**
+     * Override for Stream::write().
+     *
+     * We attempt to collect bytes before pushing them to the UART RX
+     * characteristic--writing to the RX characteristic will then generate
+     * notifications for the client. Updates made in quick succession to a
+     * notification-generating characteristic will result in data being buffered
+     * in the bluetooth stack as notifications are sent out. The stack will have
+     * 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 will need 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 Amount of characters to be appended.
+     * @return        Amount of characters appended to the rxCharacteristic.
+     */
+    virtual ssize_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.updateCharacteristicValue(getRXCharacteristicHandle(), static_cast<const uint8_t *>(sendBuffer), sendBufferIndex);
+                    sendBufferIndex = 0;
+                }
+            }
+        }
+
+        return origLength;
+    }
+
+    /**
+     * 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.
+     */
+    virtual int _putc(int c) {
+        return (write(&c, 1) == 1) ? 1 : EOF;
+    }
+
+    virtual int _getc() {
+        if (receiveBufferIndex == numBytesReceived) {
+            return EOF;
+        }
+
+        return receiveBuffer[receiveBufferIndex++];
+    }
+
+    virtual int isatty() {
+        return 1;
+    }
+
+private:
+    BLEDevice          &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__*/
+