add air530 gps sleep support

src/gps/Air530GPS.cpp

@@ -0,0 +1,87 @@
+#include "Air530GPS.h"
+#include <assert.h>
+
+/*
+Helpful translations from the Air530 GPS datasheet
+
+Sat acquision mode
+捕获电流值@3.3v 42.6 mA
+
+sat tracking mode
+跟踪电流值@3.3v 36.7 mA
+
+Low power mode
+低功耗模式@3.3V 0.85 mA
+(发送指令:$PGKC051,0)
+
+Super low power mode
+超低功耗模式@3.3V 31 uA
+(发送指令:$PGKC105,4)
+
+To exit sleep use WAKE pin
+
+Commands to enter sleep
+6、Command: 105
+进入周期性低功耗模式
+Arguments:
+
+Arg1: “0”,正常运行模式 (normal mode)
+“1”,周期超低功耗跟踪模式,需要拉高 WAKE 来唤醒 (periodic low power tracking mode - keeps sat positions, use wake to wake up)
+“2”,周期低功耗模式 (periodic low power mode)
+“4”,直接进入超低功耗跟踪模式,需要拉高 WAKE 来唤醒 (super low power consumption mode immediately, need WAKE to resume)
+“8”,自动低功耗模式,可以通过串口唤醒 (automatic low power mode, wake by sending characters to serial port)
+“9”, 自动超低功耗跟踪模式,需要拉高 WAKE 来唤醒 (automatic low power tracking when possible, need wake pin to resume)
+
+(Arg 2 & 3 only valid if Arg1 is "1" or "2")
+Arg2:运行时间(毫秒),在 Arg1 为 1、2 的周期模式下,此参数起作用
+ON time in msecs
+
+Arg3:睡眠时间(毫秒),在 Arg1 为 1、2 的周期模式下,此参数起作用
+Sleep time in msecs
+
+Example:
+$PGKC105,8*3F<CR><LF>
+This will set automatic low power mode with waking when we send chars to the serial port.  Possibly do this as soon as we get a
+new location.  When we wake again in a minute we send a character to wake up.
+
+*/
+
+
+void Air530GPS::sendCommand(const char *cmd) {
+    uint8_t sum = 0;
+
+    // Skip the $
+    assert(cmd[0] == '$');
+    const char *p = cmd + 1;
+    while(*p)
+        sum ^= *p++;
+
+    assert(_serial_gps);
+   
+    _serial_gps->write(cmd);
+    _serial_gps->printf("*%02x\r\n", sum);
+
+    // DEBUG_MSG("xsum %02x\n", sum);
+}
+
+void Air530GPS::sleep() {
+#ifdef PIN_GPS_WAKE
+    digitalWrite(PIN_GPS_WAKE, 0);
+    pinMode(PIN_GPS_WAKE, OUTPUT);
+    sendCommand("$PGKC105,4");
+#endif
+}
+
+/// wake the GPS into normal operation mode
+void Air530GPS::wake()
+{
+#if 0
+#ifdef PIN_GPS_WAKE
+    digitalWrite(PIN_GPS_WAKE, 1);
+    pinMode(PIN_GPS_WAKE, OUTPUT);
+#endif
+#else
+    // For power testing
+    sleep();
+#endif
+}