diff --git a/firmware/main.c b/firmware/main.c
index 9d1d016..6021385 100644
--- a/firmware/main.c
+++ b/firmware/main.c
@@ -8,12 +8,18 @@ int main(void) {
 
     twi_init();
 
-    si5351_init(25000000, 400000000, 300000000);
-    si5351_ms_set_source(SI5351_MS0, SI5351_PLLB);
-    si5351_ms_set_freq(SI5351_MS0, 7165000);
+    si5351_init(25000000, 800000000, 500000000);
+    si5351_ms_set_source(SI5351_MS0, SI5351_PLLA);
+    uint32_t base = 7165000;
+    uint32_t ppm_err = 9;
+    uint32_t err = base * ppm_err / 1000000;
+    uint32_t target = base - err;
+
+    si5351_ms_set_freq(SI5351_MS0, target);
     si5351_ms_enable_output(SI5351_MS0);
 
 
 
+
     while(1);
 }
diff --git a/firmware/scripts/parameter_test.py b/firmware/scripts/parameter_test.py
new file mode 100644
index 0000000..ab72569
--- /dev/null
+++ b/firmware/scripts/parameter_test.py
@@ -0,0 +1,43 @@
+#!/usr/bin/env python3
+
+import numpy as np
+import matplotlib.pyplot as plt
+
+PLL_FREQ = 800*10**6 # Mhz
+
+def main():
+    # 8kHz to 150MHz
+    out_freq = np.uint32(np.arange(1*10**6, 160*10**6, 10))
+
+    fdiv = PLL_FREQ / out_freq
+    rm = PLL_FREQ % out_freq
+
+    c = np.uint32(0x0FFFFF);
+    a = np.uint32(fdiv)
+    b = np.uint32(np.uint64(c) * np.uint64(rm) / out_freq)
+
+    ideal_freq = PLL_FREQ / fdiv
+    real_freq = PLL_FREQ / (a + b/c)
+
+    err = (ideal_freq - real_freq)
+    out_freq = out_freq / 10**6
+    ideal_freq = ideal_freq / 10**6
+    real_freq = real_freq / 10**6
+
+
+    p1  = 128 * a + np.floor(128 * b / c) - 512;
+    p2 = 128 * b - c * np.uint32(128 * b / c);
+
+
+    #plt.plot(out_freq, ideal_freq)
+    #plt.plot(out_freq, real_freq)
+
+    plt.plot(out_freq, err)
+
+
+
+
+    plt.show()
+
+if __name__ == '__main__':
+    main()
diff --git a/firmware/scripts/wspr_params.py b/firmware/scripts/wspr_params.py
new file mode 100644
index 0000000..10d96c4
--- /dev/null
+++ b/firmware/scripts/wspr_params.py
@@ -0,0 +1,44 @@
+#!/usr/bin/env python3
+from fractions import Fraction
+from math import floor
+
+
+PLL_FREQ = 900.0 * 10**6
+
+SYMBOL_COUNT = 4
+# http://www.g4jnt.com/wspr_coding_process.pdf
+FREQ_SHIFT = Fraction(12000,8192) # What the fractional fuck?
+
+# 7.040000 - 7.040200
+BASE_FREQ = 7.040100 * 10**6
+
+# Maximum c
+MAX_DENOM = 0x0FFFFF
+
+
+def main():
+    print("struct si5351_params wspr_symbols[%d] = {" % SYMBOL_COUNT)
+
+    for i in range(0, SYMBOL_COUNT):
+        symbol_freq = Fraction(BASE_FREQ) + Fraction(i) * FREQ_SHIFT
+
+        divider = Fraction(PLL_FREQ) / symbol_freq
+        divider = divider.limit_denominator(MAX_DENOM)
+
+        a = floor(divider.numerator / divider.denominator)
+        b = divider.numerator % divider.denominator
+        c = divider.denominator
+
+        print("\t// %f: %d + %d / %d" % (symbol_freq, a, b, c))
+
+        # See https://www.silabs.com/documents/public/application-notes/AN619.pdf
+        p1 = 128 * a + floor(128 * b/c) + 512
+        p2 = 128 * b - c * floor(128 * b/c)
+        p3 = c
+
+        print("\t{%d, %d, %d}," % (p1, p2, p3))
+
+    print("}")
+
+if __name__ == '__main__':
+    main()
diff --git a/firmware/si5351.c b/firmware/si5351.c
index 9e88960..0542097 100644
--- a/firmware/si5351.c
+++ b/firmware/si5351.c
@@ -62,7 +62,8 @@ void si5351_ms_set_freq(enum si5351_multisynth synth, uint32_t freq) {
     //TODO: Find better way to determine c and b
     uint32_t c = 0x0FFFFF;
     uint32_t a = fdiv;
-    uint32_t b = (uint32_t) ((uint64_t) rm * (uint64_t) c / (uint64_t) freq);
+    uint32_t b = (uint32_t) ((uint64_t) rm * (uint64_t) c /  freq);
+
     uint32_t p1  = 128 * a + (128 * b / c) - 512;
     uint32_t p2 = 128 * b - c * (128 * b / c);
     uint32_t p3 = c;
diff --git a/firmware/test b/firmware/test
new file mode 100755
index 0000000..007eb2f
Binary files /dev/null and b/firmware/test differ