Added gridlocator calculation

Cargo.toml

@@ -18,6 +18,8 @@ stm32f1xx-hal = { version = "~0.6.1", features = ["stm32f103", "rt"] }
 embedded-hal = {version = "~0.2.3"}
 nb = "~1.0.0"
 nmea0183 = "~0.2.3"
+arrayvec = {version = "~0.7.0", default-features = false}
+
 
 [features]
 # set logging levels here

src/lib.rs

@@ -5,6 +5,7 @@ use panic_probe as _;
 use stm32f1xx_hal as _;
 
 pub mod application;
+pub mod loc;
 pub mod time;
 
 // same panicking *behavior* as `panic-probe` but doesn't print a panic message

src/loc.rs

@@ -0,0 +1,40 @@
+use arrayvec::ArrayString;
+
+const FIELD_SYMBOLS: &str = "ABCDEFGHIJKLMNOPQR";
+const SUBSQUARE_SYMBOLS: &str = "abcdefghijklmnopqrstuvwx";
+
+pub fn locator_from_coordinates(lat: f32, long: f32) -> ArrayString<6> {
+    let mut target_buf = ArrayString::<6>::new();
+
+    let false_east = if long < 180.0 {
+        long + 180.0
+    } else {
+        long - 180.0
+    };
+
+    let false_north = if lat < 90.0 { lat + 90.0 } else { lat - 90.0 };
+
+    let long_field = ((false_east / 20.0) as usize);
+    let mut long_rest = false_east % 20.0;
+    target_buf.push(FIELD_SYMBOLS.chars().nth(long_field).unwrap());
+
+    let lat_field = ((false_north / 10.0) as usize);
+    let mut lat_rest = false_north % 10.0;
+    target_buf.push(FIELD_SYMBOLS.chars().nth(lat_field).unwrap());
+
+    let long_square = (long_rest / 2.0) as u32;
+    long_rest = long_rest % 2.0;
+    target_buf.push(char::from_digit(long_square, 10).unwrap());
+
+    let lat_square = (lat_rest / 1.0) as u32;
+    lat_rest = lat_rest % 1.0;
+    target_buf.push(char::from_digit(lat_square, 10).unwrap());
+
+    let long_subsquare = (long_rest / 2.0 * 24.0) as usize;
+    target_buf.push(SUBSQUARE_SYMBOLS.chars().nth(long_subsquare).unwrap());
+
+    let lat_subsquare = (lat_rest / 1.0 * 24.0) as usize;
+    target_buf.push(SUBSQUARE_SYMBOLS.chars().nth(lat_subsquare).unwrap());
+
+    return target_buf;
+}

testsuite/Cargo.toml

@@ -7,7 +7,7 @@ edition = "2018"
 version = "0.1.0"
 
 [[test]]
-name = "test"
+name = "loc"
 harness = false
 
 [dependencies]
@@ -18,6 +18,7 @@ defmt = "0.2.0"
 defmt-rtt = "0.2.0"
 defmt-test = "0.2.0"
 panic-probe = { version = "0.2.0", features = ["print-defmt"] }
+arrayvec = {version = "~0.7.0", default-features = false}
 
 [features]
 # set logging levels here

testsuite/tests/loc.rs

@@ -7,15 +7,14 @@ use wspr_beacon as _; // memory layout + panic handler
 // feature)
 #[defmt_test::tests]
 mod tests {
+    use arrayvec::ArrayString;
     use defmt::{assert, assert_eq};
+    use wspr_beacon::loc;
 
     #[test]
     fn assert_true() {
-        assert!(true)
-    }
+        let res = loc::locator_from_coordinates(49.4395, 7.7635);
 
-    #[test]
-    fn assert_eq() {
-        assert_eq!(24, 42, "TODO: write actual tests")
+        assert_eq!(res.as_str(), "JN39vk")
     }
 }