Add Serial.flush() to allow us to wait for transmission on a device to finish

Author: gfwilliams

ChangeLog

@@ -25,6 +25,7 @@
             ESP32: Advertising name is now 'Espruino abcd'
             ESP32: BLUETOOTH UART IS ENABLED BY DEFAULT - disable with `NRF.setServices({},{uart:false})`
             Bangle.js: GPS event now works even if only GGA NMEA events are enabled (which you might do for speed)
+            Add Serial.flush() to allow us to wait for transmission on a device to finish
 
      2v17 : Bangle.js: When reading file info from a filename table, do it in blocks of 8 (20% faster file search)
             Bangle.js2: Increase flash buffer size from 16->32 bytes (5% performance increase)

src/jsdevices.c

@@ -284,12 +284,10 @@ IOEventFlags jshGetDeviceToTransmit() {
 }
 
 /**
- * Try and get a character for transmission.
+ * Try and get a character for transmission on a device.
  * \return The next byte to transmit or -1 if there is none.
  */
-int jshGetCharToTransmit(
-    IOEventFlags device // The device being looked at for a transmission.
-  ) {
+int jshGetCharToTransmit(IOEventFlags device) {
   if (DEVICE_HAS_DEVICE_STATE(device)) {
     volatile JshSerialDeviceState *deviceState = &jshSerialDeviceStates[TO_SERIAL_DEVICE_STATE(device)];
     if ((*deviceState)&SDS_XOFF_PENDING) {
@@ -324,12 +322,32 @@ int jshGetCharToTransmit(
   return -1; // no data :(
 }
 
+/// Wait for all data in the transmit queue to be written
 void jshTransmitFlush() {
   jsiSetBusy(BUSY_TRANSMIT, true);
   while (jshHasTransmitData()) ; // wait for send to finish
   jsiSetBusy(BUSY_TRANSMIT, false);
 }
 
+/// Wait for all data in the transmit queue to be written for a specific device
+void jshTransmitFlushDevice(IOEventFlags device) {
+  jsiSetBusy(BUSY_TRANSMIT, true);
+  bool deviceHasData = false;
+  do {
+    deviceHasData = false;    
+    // Check TX queue to see if there is any data to send
+    unsigned char tempTail = txTail;
+    while (txHead != tempTail) {
+      if (IOEVENTFLAGS_GETTYPE(txBuffer[tempTail].flags) == device) {
+        deviceHasData = true;
+        break;        
+      }
+      tempTail = (unsigned char)((tempTail+1)&TXBUFFERMASK);
+    }
+  } while (deviceHasData);
+  jsiSetBusy(BUSY_TRANSMIT, false);
+}
+
 /**
  * Discard all the data waiting for transmission.
  */

src/jsdevices.h

@@ -217,6 +217,8 @@ void jshTransmit(IOEventFlags device, unsigned char data);
 void jshTransmitPrintf(IOEventFlags device, const char *fmt, ...);
 /// Wait for transmit to finish
 void jshTransmitFlush();
+/// Wait for all data in the transmit queue to be written for a specific device
+void jshTransmitFlushDevice(IOEventFlags device);
 /// Clear everything from a device
 void jshTransmitClearDevice(IOEventFlags device);
 /// Move all output from one device to another

src/jswrap_serial.c

@@ -539,3 +539,19 @@ Return a string containing characters that have been received
 }
 Pipe this USART to a stream (an object with a 'write' method)
  */
+
+
+/*JSON{
+  "type" : "method",
+  "class" : "Serial",
+  "name" : "flush",
+  "ifndef" : "SAVE_ON_FLASH",
+  "generate" : "jswrap_serial_flush"
+}
+Flush this serial stream (pause execution until all data has been sent)
+ */
+void jswrap_serial_flush(JsVar *parent) {
+  IOEventFlags device = jsiGetDeviceFromClass(parent);
+  if (device == EV_NONE) return;
+  jshTransmitFlushDevice(device);
+}

src/jswrap_serial.h

@@ -25,5 +25,6 @@ void jswrap_serial_print(JsVar *parent, JsVar *str);
 void jswrap_serial_println(JsVar *parent, JsVar *str);
 void jswrap_serial_write(JsVar *parent, JsVar *data);
 void jswrap_serial_inject(JsVar *parent, JsVar *args);
+void jswrap_serial_flush(JsVar *parent);
 
 #endif // JSWRAP_SERIAL_H_