diff --git a/firmware/include/wspr.h b/firmware/include/wspr.h
index 1f6fb1c..78018f3 100644
--- a/firmware/include/wspr.h
+++ b/firmware/include/wspr.h
@@ -6,40 +6,11 @@
 
 #include "si5351.h"
 
+#define WSPR_LENGTH 162
 
-// For PLL with 800MHz
-static const struct si5351_params WSPR_SYMBOLS[4] = {
-	// 7040100.000000: 113 + 44687 / 70401
-	// actual: 7040100.000000
-	{14033, 17455, 70401},
-	// 7040101.464844: 113 + 447801 / 705503
-	// actual: 7040101.464844
-	{14033, 172785, 705503},
-	// 7040102.929688: 113 + 38515 / 60682
-	// actual: 7040102.929688
-	{14033, 14678, 60682},
-	// 7040104.394531: 113 + 123233 / 194166
-	// actual: 7040104.394531
-	{14033, 46378, 194166},
-};
-
-
-static const uint8_t WSPR_LENGTH = 162;
-static const uint16_t WSPR_PERIOD = 683;
-
-// DL1SSK at JN39we
-static uint8_t default_wspr_msg[162] = {
-	1, 1, 0, 0, 2, 0, 0, 2, 1, 0, 0, 0, 1, 3, 3, 2, 2, 2, 3, 2, 0, 1, 0, 3, 1, 1, 1, 0, 2,
-	2, 0, 2, 2, 0, 3, 0, 0, 1, 0, 3, 2, 0, 0, 0, 0, 0, 3, 0, 1, 1, 0, 0, 3, 1, 2, 1, 0, 2,
-	2, 3, 1, 2, 1, 2, 2, 2, 2, 3, 3, 2, 1, 2, 1, 2, 1, 2, 3, 2, 0, 3, 2, 0, 1, 0, 3, 3, 0,
-	2, 2, 1, 1, 2, 1, 0, 1, 0, 2, 0, 1, 2, 2, 2, 0, 0, 3, 2, 2, 3, 0, 0, 1, 3, 3, 2, 3, 3,
-	0, 2, 3, 1, 2, 1, 0, 2, 2, 3, 3, 3, 0, 2, 2, 0, 2, 1, 2, 1, 2, 0, 1, 3, 0, 0, 0, 0, 0,
-	2, 0, 3, 1, 0, 1, 2, 3, 1, 2, 2, 2, 1, 1, 0, 0, 2
-};
-
-
-
+void wspr_encode(char *call, char *loc, uint8_t power, uint8_t *buffer);
 void wspr_transmit(enum si5351_multisynth synth, uint8_t *msg);
 
 
+
 #endif
diff --git a/firmware/main.c b/firmware/main.c
index 4c7334b..7a55f3e 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -19,7 +19,10 @@ int main(void) {
     //si5351_ms_write_params(SI5351_MS0, WSPR_SYMBOLS[3]);
 
 
-    wspr_transmit(SI5351_MS0, default_wspr_msg);
+    uint8_t wspr_buffer[WSPR_LENGTH];
+
+    wspr_encode("DL1SSK", "JN39", 27, wspr_buffer);
+    wspr_transmit(SI5351_MS0, wspr_buffer);
 
 
     while(1);
diff --git a/firmware/wspr.c b/firmware/wspr.c
index b5d0e79..6e62830 100644
--- a/firmware/wspr.c
+++ b/firmware/wspr.c
@@ -1,7 +1,161 @@
 #include "wspr.h"
 
-#include <util/delay.h>
+#include <ctype.h>
 
+#include <util/delay.h>
+#include <avr/pgmspace.h>
+#include <string.h>
+
+
+
+const uint8_t WSPR_SYNC[WSPR_LENGTH] PROGMEM = {
+	1,1,0,0,0,0,0,0,1,0,0,0,1,1,1,0,0,0,1,0,0,1,0,1,1,1,1,0,0,0,0,0,0,0,1,0,0,1,0,1,0,0,
+	0,0,0,0,1,0,1,1,0,0,1,1,0,1,0,0,0,1,1,0,1,0,0,0,0,1,1,0,1,0,1,0,1,0,1,0,0,1,0,0,1,0,
+	1,1,0,0,0,1,1,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,0,1,0,0,1,1,1,0,1,1,0,0,1,1,0,1,0,0,0,1,
+	1,1,0,0,0,0,0,1,0,1,0,0,1,1,0,0,0,0,0,0,0,1,1,0,1,0,1,1,0,0,0,1,1,0.0,0
+};
+
+static inline uint8_t wspr_call_char(char c) {
+	c = toupper(c);
+	if(c >= '0' && c <= '9') {
+		return c - '0';
+	}
+	else if(c >= 'A' && c <= 'Z') {
+		return 10 + (c - 'A');
+	}
+	// Turn everything else to space
+	else {
+		return 36;
+	}
+}
+
+static inline uint8_t wspr_loc_char(char c) {
+	c = toupper(c);
+	if(c >= '0' && c <= '9') {
+		return c - '0';
+	}
+	else if(c >= 'A' && c <= 'R') {
+		return c - 'A';
+	}
+	// Everthing else becomes 9/I
+	else {
+		return 9;
+	}
+}
+
+static inline uint8_t wspr_power(uint8_t power) {
+	if(power > 60) {
+		return 60;
+	}
+	return power;
+}
+
+const uint8_t WSPR_POWER_LOC_BITS = 22;
+uint64_t wspr_message(char *call, char *loc, uint8_t power) {
+	uint32_t m, n;
+
+	n = wspr_call_char(call[0]);
+	n = n * 36 + wspr_call_char(call[1]);
+	n = n * 10 + wspr_call_char(call[2]);
+	n = n * 27 + wspr_call_char(call[3]) - 10;
+	n = n * 27 + wspr_call_char(call[4]) - 10;
+	n = n * 27 + wspr_call_char(call[5]) - 10;
+
+	m = 179 - 10 * wspr_loc_char(loc[0]) - wspr_loc_char(loc[2]);
+	m = m * 180 + 10 * wspr_loc_char(loc[1]) + wspr_loc_char(loc[3]);
+	m = m * 128 + wspr_power(power) + 64;
+
+	return ((uint64_t) n) << WSPR_POWER_LOC_BITS | m;
+}
+
+
+const uint32_t WSPR_FEC_TAPS1 = 0xF2D05351;
+const uint32_t WSPR_FEC_TAPS2 = 0xE4613C47;
+
+uint8_t wspr_parity32(uint32_t x) {
+	x ^= x >> 16;
+    x ^= x >> 8;
+    x ^= x >> 4;
+    x ^= x >> 2;
+    x ^= x >> 1;
+	return x & 1;
+}
+
+void wspr_fec(uint64_t msg, uint8_t *output) {
+	memset(output, 0, WSPR_LENGTH);
+
+	uint32_t reg = 0;
+	for(uint8_t i = 0;  i < 81; i++) {
+		uint8_t bit = 0;
+		if(i < 50) {
+			bit = (msg >> (50 - i - 1)) & 1;
+		}
+
+		reg = (reg << 1) | bit;
+
+		uint32_t tabs1 = reg & WSPR_FEC_TAPS1;
+		uint32_t tabs2 = reg & WSPR_FEC_TAPS2;
+
+		output[i * 2] = wspr_parity32(tabs1);
+		output[i * 2 + 1] = wspr_parity32(tabs2);
+	}
+}
+
+uint8_t wspr_reverse_bits(uint8_t bits) {
+	//https://gcc.gnu.org/onlinedocs/gcc-4.7.1/gcc/AVR-Built_002din-Functions.html
+	return __builtin_avr_insert_bits (0x01234567, bits, 0);
+}
+
+
+void wspr_interleave(uint8_t *input, uint8_t *output) {
+	uint8_t p = 0;
+	uint8_t i = 0;
+	while(p < WSPR_LENGTH) {
+		uint8_t rev_i = wspr_reverse_bits(i);
+		if(rev_i < WSPR_LENGTH) {
+			output[rev_i] = input[p];
+			p++;
+		}
+		i++;
+	}
+}
+
+void wspr_add_sync(uint8_t *symbols) {
+	for(uint8_t i = 0; i < WSPR_LENGTH; i++) {
+		symbols[i] = pgm_read_byte(&(WSPR_SYNC[i])) + 2 * symbols[i];
+	}
+}
+
+
+void wspr_encode(char *call, char *loc, uint8_t power, uint8_t *buffer) {
+	uint8_t tmp_buffer[WSPR_LENGTH];
+
+	uint64_t msg = wspr_message(call, loc, power);
+	wspr_fec(msg, tmp_buffer);
+	wspr_interleave(tmp_buffer, buffer);
+	wspr_add_sync(buffer);
+}
+
+
+
+// For PLL with 800MHz
+const struct si5351_params WSPR_SYMBOLS[4] = {
+	// 7040100.000000: 113 + 44687 / 70401
+	// actual: 7040100.000000
+	{14033, 17455, 70401},
+	// 7040101.464844: 113 + 447801 / 705503
+	// actual: 7040101.464844
+	{14033, 172785, 705503},
+	// 7040102.929688: 113 + 38515 / 60682
+	// actual: 7040102.929688
+	{14033, 14678, 60682},
+	// 7040104.394531: 113 + 123233 / 194166
+	// actual: 7040104.394531
+	{14033, 46378, 194166},
+};
+
+
+const uint16_t WSPR_PERIOD = 683;
 
 void wspr_transmit(enum si5351_multisynth synth, uint8_t *msg) {
 	si5351_ms_enable_output(synth);