use power of 2 element FFT

howard0su · Apr 27, 2022 · 214ea4c · 214ea4c
1 parent 6153396
commit 214ea4c
Showing 1 changed file with 7 additions and 1 deletion.
diff --git a/decode_ft8.c b/decode_ft8.c
@@ -115,7 +115,13 @@ void monitor_init(monitor_t* me, const monitor_config_t* cfg)
     // Compute DSP parameters that depend on the sample rate
     me->block_size = (int)(cfg->sample_rate * symbol_period); // samples corresponding to one FSK symbol
     me->subblock_size = me->block_size / cfg->time_osr;
-    me->nfft = me->block_size * cfg->freq_osr;
+    if (me->block_size * cfg->freq_osr < 2048)
+        me->nfft = 2048;
+    else if (me->block_size * cfg->freq_osr < 4096)
+        me->nfft = 4096;
+    else if (me->block_size * cfg->freq_osr < 8192)
+        me->nfft = 8192;
+
     me->fft_norm = 2.0f / me->nfft;
     // const int len_window = 1.8f * me->block_size; // hand-picked and optimized