From 83015ff0225dc96168d60effafd670604ac48b5d Mon Sep 17 00:00:00 2001
From: s3lph <s3lph@kabelsalat.ch>
Date: Mon, 29 May 2023 02:35:07 +0200
Subject: [PATCH] fix: air530 behaves a bit differently than described in the
 datasheet

---
 platformio.ini |  2 +-
 src/main.cpp   | 63 ++++++++++++++++++++++++++++----------------------
 2 files changed, 36 insertions(+), 29 deletions(-)

diff --git a/platformio.ini b/platformio.ini
index f93ba2c..305c957 100644
--- a/platformio.ini
+++ b/platformio.ini
@@ -15,7 +15,7 @@ framework = arduino
 lib_deps =
     https://github.com/marcoschwartz/LiquidCrystal_I2C
     https://github.com/rocketscream/Low-Power
-build_flags = -DGPSM_UBLOX6
+build_flags = -DGPSM_AIR530
 upload_protocol = custom
 upload_flags =
     -C
diff --git a/src/main.cpp b/src/main.cpp
index 8442d58..20f7c14 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -541,9 +541,18 @@ uint8_t nmeaState = 0;
 char nmeaStr[256]; // NMEA-0183 messages should only be 82 characters, but the NEO-6M sends much longer messages
 char *sptr;
 void readNmeaRmc() {
+  if (nmeaState == 3) {
+    nmeaState = 0;
+  }
 
-  while (Serial.available()) {
+  if (!Serial.available()) {
+    return;
+  }
+  while (nmeaState != 3) {
     int16_t byt = Serial.read();
+    if (byt == -1) {
+      continue;
+    }
     if (byt == '$') {
       nmeaState = 1;
       sptr = nmeaStr;
@@ -551,14 +560,14 @@ void readNmeaRmc() {
     if (nmeaState == 1) {
       *(sptr++) = (char) byt;
       if (sptr >= nmeaStr + sizeof(nmeaStr)) {
-	nmeaState = 0;
+	nmeaState = 3;
       }
       if (byt == '*') {
 	*sptr = 0;
 	if (nmeaStr[3] == 'R' && nmeaStr[4] == 'M' && nmeaStr[5] == 'C') {
 	  nmeaState = 2;
 	} else {
-	  nmeaState = 0;
+	  nmeaState = 3;
 	}
       }
     }
@@ -567,11 +576,6 @@ void readNmeaRmc() {
       // L80-R: Send GPS module into standby mode
       Serial.println("$PMTK161,0*28");
       Serial.flush();
-#endif
-#if defined(GPSM_AIR530)
-      // AIR530: Send GPS module into low-power mode
-      Serial.println("$PGKC051,1*36");
-      Serial.flush();
 #endif
       char buf[16];
       char *bptr = buf;
@@ -635,7 +639,7 @@ void readNmeaRmc() {
 	} else {
 	  *bptr++ = *ptr;
 	  if (bptr >= buf + 16) {
-	    nmeaState = 0;
+	    nmeaState = 3;
 	    break;
 	  }
 	}
@@ -675,7 +679,6 @@ void readNmeaRmc() {
 	}
 	memcpy(aprs+34, config.comment, config.commentLen);
 	aprs[34+config.commentLen] = 0;
-	Serial.println(aprs);
 	// AX.25 3.8 - FCS is sent MSB first
 	uint16_t fcs = 0xffff;
 	for (size_t i = 0; i < sizeof(frame); ++i) {
@@ -701,7 +704,7 @@ void readNmeaRmc() {
 	digitalWrite(PTT_IND, LOW);
 	
       }
-      nmeaState = 0;
+      nmeaState = 3;
     }
   }
 }
@@ -729,6 +732,15 @@ void setup() {
   // AIR530: Disable all NMEA sentences except for GPRMC
   Serial.println("$PGKC242,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*36");
   Serial.flush();
+  // AIR530: Disable all NMEA sentences except for GPRMC
+  Serial.println("$PGKC242,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0*36");
+  Serial.flush();
+  // AIR530: Send NMEA sentences once every 10s
+  Serial.println("$PGKC101,10000*32");
+  Serial.flush();
+  // AIR530: Send GPS module into low-power mode
+  Serial.println("$PGKC105,8*3F");
+  Serial.flush();
 #else
   // Assume NMEA-0183 default baud rate of 4800
   Serial.begin(4800);
@@ -754,7 +766,6 @@ void setup() {
 
 
 void loop() {
-  readNmeaRmc();
   if (editingConfig) {
     editConfig();
     return;
@@ -801,22 +812,18 @@ void loop() {
   }
   LowPower.powerDown(SLEEP_8S, ADC_OFF, BOD_OFF);
   if (!abcPressed && !setPressed) {
-      off = true;
-      lcd.noDisplay();
-      lcd.noBacklight();    
+    readNmeaRmc();
+    off = true;
+    lcd.noDisplay();
+    lcd.noBacklight();    
   } else if (off) {
-      off = false;
-      abcPressed = false;
-      setPressed = false;
-      if (editingConfig || editingComment) {
-	lcd.blink();
-      }
-      lcd.backlight();
-      lcd.display();    
+    off = false;
+    abcPressed = false;
+    setPressed = false;
+    if (editingConfig || editingComment) {
+      lcd.blink();
+    }
+    lcd.backlight();
+    lcd.display();
   }
-#if defined(GPSM_AIR530)
-  // Wake AIR530
-  Serial.println();
-  Serial.flush();
-#endif
 }