Remove all debug and printf

sdk/software/examples/fft/fft.c

@@ -0,0 +1,14 @@
+#include "fft.h"
+#include "common_func.h"
+
+void fft_start() {
+    RegWrite(FFT_CSR_REG, FFT_CTRL_START);
+}
+
+void fft_wait() {
+    while ((RegRead(FFT_CSR_REG) & FFT_STAT_DONE) == 0) {}
+}
+
+unsigned int fft_get_csr() {
+    return RegRead(FFT_CSR_REG);
+}