travis build

different configurations are specified in the configurations directory
 to select one copy it replcing the config.h file (as the travis script does)
 or change the include file directive in crossbow.ino

crossbow/sbus.cpp

@@ -0,0 +1,152 @@
+#include "Arduino.h"
+#include "variables.h"
+#include "sbus.h"
+
+#define SBUS_MIN_OFFSET 173
+#define SBUS_MID_OFFSET 992
+#define SBUS_MAX_OFFSET 1811
+#define SBUS_CHANNEL_NUMBER 16
+#define SBUS_PACKET_LENGTH 25
+#define SBUS_FRAME_HEADER 0x0f
+#define SBUS_FRAME_FOOTER 0x00
+#define SBUS_FRAME_FOOTER_V2 0x04
+#define SBUS_STATE_FAILSAFE 0x08
+#define SBUS_STATE_SIGNALLOSS 0x04
+
+#define SBUS_IS_RECEIVING_THRESHOLD 250 //If there is no SBUS input for 250ms, assume connection is broken
+
+/*
+Precomputed mapping from 990-2010 to 173:1811
+equivalent to 
+map(channels[i], RC_CHANNEL_MIN, RC_CHANNEL_MAX, SBUS_MIN_OFFSET, SBUS_MAX_OFFSET);
+*/
+int mapChannelToSbus(int in) {
+    return (((long) in * 1605l) / 1000l) - 1417;
+}
+
+int mapSbusToChannel(int in) {
+    //TODO, speed up this processing
+    return map(in, 173, 1811, 990, 2010);
+}
+
+void sbusPreparePacket(uint8_t packet[], int16_t channels[], bool isSignalLoss, bool isFailsafe){
+    
+    static int output[SBUS_CHANNEL_NUMBER] = {0};
+    
+    /*
+     * Map 1000-2000 with middle at 1500 chanel values to
+     * 173-1811 with middle at 992 S.BUS protocol requires
+     */
+    for (uint8_t i = 0; i < SBUS_CHANNEL_NUMBER; i++) {
+        output[i] = mapChannelToSbus(channels[i]);
+    }
+
+    uint8_t stateByte = 0x00;
+    if (isSignalLoss) {
+        stateByte |= SBUS_STATE_SIGNALLOSS;
+    }
+    if (isFailsafe) {
+        stateByte |= SBUS_STATE_FAILSAFE;
+    }
+    packet[0] = SBUS_FRAME_HEADER; //Header
+    
+    packet[1] = (uint8_t) (output[0] & 0x07FF);
+    packet[2] = (uint8_t) ((output[0] & 0x07FF)>>8 | (output[1] & 0x07FF)<<3);
+    packet[3] = (uint8_t) ((output[1] & 0x07FF)>>5 | (output[2] & 0x07FF)<<6);
+    packet[4] = (uint8_t) ((output[2] & 0x07FF)>>2);
+    packet[5] = (uint8_t) ((output[2] & 0x07FF)>>10 | (output[3] & 0x07FF)<<1);
+    packet[6] = (uint8_t) ((output[3] & 0x07FF)>>7 | (output[4] & 0x07FF)<<4);
+    packet[7] = (uint8_t) ((output[4] & 0x07FF)>>4 | (output[5] & 0x07FF)<<7);
+    packet[8] = (uint8_t) ((output[5] & 0x07FF)>>1);
+    packet[9] = (uint8_t) ((output[5] & 0x07FF)>>9 | (output[6] & 0x07FF)<<2);
+    packet[10] = (uint8_t) ((output[6] & 0x07FF)>>6 | (output[7] & 0x07FF)<<5);
+    packet[11] = (uint8_t) ((output[7] & 0x07FF)>>3);
+    packet[12] = (uint8_t) ((output[8] & 0x07FF));
+    packet[13] = (uint8_t) ((output[8] & 0x07FF)>>8 | (output[9] & 0x07FF)<<3);
+    packet[14] = (uint8_t) ((output[9] & 0x07FF)>>5 | (output[10] & 0x07FF)<<6);  
+    packet[15] = (uint8_t) ((output[10] & 0x07FF)>>2);
+    packet[16] = (uint8_t) ((output[10] & 0x07FF)>>10 | (output[11] & 0x07FF)<<1);
+    packet[17] = (uint8_t) ((output[11] & 0x07FF)>>7 | (output[12] & 0x07FF)<<4);
+    packet[18] = (uint8_t) ((output[12] & 0x07FF)>>4 | (output[13] & 0x07FF)<<7);
+    packet[19] = (uint8_t) ((output[13] & 0x07FF)>>1);
+    packet[20] = (uint8_t) ((output[13] & 0x07FF)>>9 | (output[14] & 0x07FF)<<2);
+    packet[21] = (uint8_t) ((output[14] & 0x07FF)>>6 | (output[15] & 0x07FF)<<5);
+    packet[22] = (uint8_t) ((output[15] & 0x07FF)>>3);
+    
+    packet[23] = stateByte; //Flags byte
+    packet[24] = SBUS_FRAME_FOOTER; //Footer
+}
+
+SbusInput::SbusInput(HardwareSerial &serial) : _serial(serial)
+{
+}
+
+
+void SbusInput::loop(void)
+{
+    if (_serial.available()) {
+        sbusRead();
+    }
+}
+
+void SbusInput::start(void)
+{
+        _serial.begin(100000, SERIAL_8N2);
+}
+
+void SbusInput::sbusRead() {
+    static byte buffer[25];
+	static byte buffer_index = 0;
+
+    static uint32_t _decoderErrorFrames;
+    static uint32_t _goodFrames;
+
+	while (_serial.available()) {
+		byte rx = _serial.read();
+		if (buffer_index == 0 && rx != SBUS_FRAME_HEADER) {
+			//incorrect start byte, out of sync
+			_decoderErrorFrames++;
+			continue;
+		}
+
+        buffer[buffer_index] = rx;
+        buffer_index++;
+
+		if (buffer_index == 25) {
+			buffer_index = 0;
+			if (buffer[24] != SBUS_FRAME_FOOTER) {
+				//incorrect end byte, out of sync
+				_decoderErrorFrames++;
+				continue;
+			}
+			_goodFrames++;
+
+			channels[0]  = ((buffer[1]    |buffer[2]<<8)                 & 0x07FF);
+			channels[1]  = ((buffer[2]>>3 |buffer[3]<<5)                 & 0x07FF);
+			channels[2]  = ((buffer[3]>>6 |buffer[4]<<2 |buffer[5]<<10)  & 0x07FF);
+			channels[3]  = ((buffer[5]>>1 |buffer[6]<<7)                 & 0x07FF);
+			channels[4]  = ((buffer[6]>>4 |buffer[7]<<4)                 & 0x07FF);
+			channels[5]  = ((buffer[7]>>7 |buffer[8]<<1 |buffer[9]<<9)   & 0x07FF);
+			channels[6]  = ((buffer[9]>>2 |buffer[10]<<6)                & 0x07FF);
+			channels[7]  = ((buffer[10]>>5|buffer[11]<<3)                & 0x07FF);
+			channels[8]  = ((buffer[12]   |buffer[13]<<8)                & 0x07FF);
+			channels[9]  = ((buffer[13]>>3|buffer[14]<<5)                & 0x07FF);
+			channels[10] = ((buffer[14]>>6|buffer[15]<<2|buffer[16]<<10) & 0x07FF);
+			channels[11] = ((buffer[16]>>1|buffer[17]<<7)                & 0x07FF);
+			channels[12] = ((buffer[17]>>4|buffer[18]<<4)                & 0x07FF);
+			channels[13] = ((buffer[18]>>7|buffer[19]<<1|buffer[20]<<9)  & 0x07FF);
+			channels[14] = ((buffer[20]>>2|buffer[21]<<6)                & 0x07FF);
+			channels[15] = ((buffer[21]>>5|buffer[22]<<3)                & 0x07FF);
+
+			for (uint8_t channelIndex = 0; channelIndex < SBUS_CHANNEL_NUMBER; channelIndex++) {
+                channels[channelIndex] = mapSbusToChannel(channels[channelIndex]);
+            }
+
+			_lastChannelReceivedAt = millis();
+        }
+	}
+}
+
+bool SbusInput::isReceiving() {
+    return  !(millis() - _lastChannelReceivedAt > SBUS_IS_RECEIVING_THRESHOLD);
+}