add ability to read a characteristic

Author: gfwilliams

libs/bluetooth/jswrap_bluetooth.c

@@ -1046,6 +1046,26 @@ Web Bluetooth-style GATT characteristic - get this using `BluetoothRemoteGATTSer
     ],
     "return" : ["JsVar", "A Promise that is resolved (or rejected) when the characteristic is written" ]
 }
+
+Write a characteristic's value
+
+```
+var device;
+NRF.connect(device_address).then(function(d) {
+  device = d;
+  return d.getPrimaryService("service_uuid);
+}).then(function(s) {
+  console.log("Service ",s);
+  return s.getCharacteristic(characteristic_uuid);
+}).then(function(c) {
+  return c.writeValue("Hello");
+}).then(function(d) {
+  device.disconnect();
+}).catch(function() {
+  console.log("Something's broken.");
+});
+```
+
 **Note:** This is only available on some devices
 */
 JsVar *jswrap_nrf_BluetoothRemoteGATTCharacteristic_writeValue(JsVar *characteristic, JsVar *data) {
@@ -1063,7 +1083,48 @@ JsVar *jswrap_nrf_BluetoothRemoteGATTCharacteristic_writeValue(JsVar *characteri
   return 0;
 #endif
 }
+/*JSON{
+    "type" : "method",
+    "class" : "BluetoothRemoteGATTCharacteristic",
+    "name" : "readValue",
+    "generate" : "jswrap_nrf_BluetoothRemoteGATTCharacteristic_readValue",
+    "return" : ["JsVar", "A Promise that is resolved (or rejected) with data when the characteristic is read" ]
+}
+
+Read a characteristic's value
+
+```
+var device;
+NRF.connect(device_address).then(function(d) {
+  device = d;
+  return d.getPrimaryService("service_uuid);
+}).then(function(s) {
+  console.log("Service ",s);
+  return s.getCharacteristic(characteristic_uuid);
+}).then(function(c) {
+  return c.readValue();
+}).then(function(d) {
+  console.log("Got:", JSON.stringify(d));
+  device.disconnect();
+}).catch(function() {
+  console.log("Something's broken.");
+});
+```
+
+**Note:** This is only available on some devices
+*/
+JsVar *jswrap_nrf_BluetoothRemoteGATTCharacteristic_readValue(JsVar *characteristic) {
+#if CENTRAL_LINK_COUNT>0
+  if (!bleNewTask(BLETASK_CHARACTERISTIC_READ))
+    return 0;
 
+  jsble_central_characteristicRead(characteristic);
+  return jsvLockAgainSafe(blePromise);
+#else
+  jsExceptionHere(JSET_ERROR, "Unimplemented");
+  return 0;
+#endif
+}
 
 /* ---------------------------------------------------------------------
  *                                                               TESTING
@@ -1096,25 +1157,6 @@ NRF.connect("d1:53:36:1a:7a:17").then(function(d) {
 });
 
 
-// getting just what we want
-var device;
-NRF.connect("d1:53:36:1a:7a:17").then(function(d) {
-  device = d;
-  console.log("Connected ",d);
-  return d.getPrimaryService("6e400001-b5a3-f393-e0a9-e50e24dcca9e"); // UART
-}).then(function(s) {
-  console.log("Service ",s);
-  return s.getCharacteristic("6e400002-b5a3-f393-e0a9-e50e24dcca9e"); // RX
-}).then(function(c) {
-  console.log("Characteristic ",c);
-  return c.writeValue("LED1.set()\n");
-}).then(function() {
-  console.log("Written. Disconnecting");
-  device.disconnect();
-}).catch(function() {
-  console.log("Oops");
-});
-
 // ------------------------------ on BLE server (microbit) - allow display of data
 NRF.setServices({
   0xBCDE : {

libs/bluetooth/jswrap_bluetooth.h

@@ -20,6 +20,7 @@ typedef enum {
   BLETASK_PRIMARYSERVICE, ///< Find primary service
   BLETASK_CHARACTERISTIC,  ///< Find characteristics
   BLETASK_CHARACTERISTIC_WRITE, ///< Write to a characteristic
+  BLETASK_CHARACTERISTIC_READ, ///< Read from a characteristic
 } BleTask;
 
 bool bleInTask(BleTask task);
@@ -53,3 +54,4 @@ JsVar *jswrap_BluetoothRemoteGATTServer_getPrimaryServices(JsVar *parent);
 JsVar *jswrap_BluetoothRemoteGATTService_getCharacteristic(JsVar *parent, JsVar *characteristic);
 JsVar *jswrap_BluetoothRemoteGATTService_getCharacteristics(JsVar *parent);
 JsVar *jswrap_nrf_BluetoothRemoteGATTCharacteristic_writeValue(JsVar *characteristic, JsVar *data);
+JsVar *jswrap_nrf_BluetoothRemoteGATTCharacteristic_readValue(JsVar *characteristic);

targets/nrf5x/bluetooth.c

@@ -224,7 +224,7 @@ void SWI1_IRQHandler(bool radio_evt) {
 static void on_ble_evt(ble_evt_t * p_ble_evt)
 {
     uint32_t                         err_code;
-    // jsiConsolePrintf("\n[%d]\n", p_ble_evt->header.evt_id);
+    //jsiConsolePrintf("\n[%d]\n", p_ble_evt->header.evt_id);
 
     switch (p_ble_evt->header.evt_id) {
       case BLE_GAP_EVT_TIMEOUT:
@@ -517,6 +517,15 @@ static void on_ble_evt(ble_evt_t * p_ble_evt)
       case BLE_GATTC_EVT_DESC_DISC_RSP:
         jsiConsolePrintf("DESC\n");
         break;
+
+      case BLE_GATTC_EVT_READ_RSP: {
+        ble_gattc_evt_read_rsp_t *p_read = &p_ble_evt->evt.gattc_evt.params.read_rsp;
+        JsVar *data = jsvNewStringOfLength(p_read->len);
+        if (data) jsvSetString(data, (char*)&p_read->data[0], p_read->len);
+        bleCompleteTaskSuccess(BLETASK_CHARACTERISTIC_READ, data);
+        jsvUnLock(data);
+        break;
+      }
 #endif
 
       default:
@@ -1287,7 +1296,7 @@ void jsble_central_getCharacteristics(JsVar *service, ble_uuid_t uuid) {
   }
 }
 
- void jsble_central_characteristicWrite(JsVar *characteristic, char *dataPtr, size_t dataLen) {
+void jsble_central_characteristicWrite(JsVar *characteristic, char *dataPtr, size_t dataLen) {
   const ble_gattc_write_params_t write_params = {
         .write_op = BLE_GATT_OP_WRITE_CMD,
         .flags    = BLE_GATT_EXEC_WRITE_FLAG_PREPARED_WRITE,
@@ -1301,4 +1310,12 @@ void jsble_central_getCharacteristics(JsVar *service, ble_uuid_t uuid) {
     if (jsble_check_error(err_code))
       bleCompleteTaskFail(BLETASK_CHARACTERISTIC_WRITE, 0);
 }
+
+void jsble_central_characteristicRead(JsVar *characteristic) {
+   uint16_t handle = jsvGetIntegerAndUnLock(jsvObjectGetChild(characteristic, "handle_value", 0));
+   uint32_t              err_code;
+   err_code = sd_ble_gattc_read(m_central_conn_handle, handle, 0/*offset*/);
+   if (jsble_check_error(err_code))
+     bleCompleteTaskFail(BLETASK_CHARACTERISTIC_READ, 0);
+}
 #endif

targets/nrf5x/bluetooth.h

@@ -116,4 +116,6 @@ void jsble_central_getPrimaryServices(ble_uuid_t uuid);
 void jsble_central_getCharacteristics(JsVar *service, ble_uuid_t uuid);
 // Write data to the given characteristic. When done call bleCompleteTask
 void jsble_central_characteristicWrite(JsVar *characteristic, char *dataPtr, size_t dataLen);
+// Read data from the given characteristic. When done call bleCompleteTask
+void jsble_central_characteristicRead(JsVar *characteristic);
 #endif