1 files changed, 94 insertions, 0 deletions
diff --git a/controller/fw/src/freq_meas.c b/controller/fw/src/freq_meas.c
new file mode 100644
index 0000000..e6b3976
--- /dev/null
+++ b/controller/fw/src/freq_meas.c
@@ -0,0 +1,94 @@
+
+#include <unistd.h>
+#include <math.h>
+
+#include <arm_math.h>
+#include <levmarq.h>
+
+#include "freq_meas.h"
+#include "sr_global.h"
+
+
+/* FTT window lookup table defined in generated/fmeas_fft_window.c */
+extern const float * const fmeas_fft_window_table;
+
+/* jury-rig some definitions for these functions since the ARM headers only export an over-generalized variable bin size
+ * variant. */
+extern arm_status arm_rfft_32_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_64_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_128_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_256_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_512_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_1024_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_2048_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+extern arm_status arm_rfft_4096_fast_init_f32(arm_rfft_fast_instance_f32 * S);
+
+#define CONCAT(A, B, C) A ## B ## C
+#define arm_rfft_init_name(nbits) CONCAT(arm_rfft_, nbits, _fast_init_f32)
+
+float func_gauss_grad(float *out, float *params, int x, void *userdata);
+float func_gauss(float *params, int x, void *userdata);
+
+int adc_buf_measure_freq(uint16_t adc_buf[FMEAS_FFT_LEN], float *out) {
+    int rc;
+    float in_buf[FMEAS_FFT_LEN];
+    float out_buf[FMEAS_FFT_LEN];
+    for (size_t i=0; i<FMEAS_FFT_LEN; i++)
+        in_buf[i] = (float)adc_buf[i] / (float)FMEAS_ADC_MAX * fmeas_fft_window_table[i];
+
+    arm_rfft_fast_instance_f32 fft_inst;
+    if ((rc = arm_rfft_init_name(FMEAS_FFT_LEN)(&fft_inst)) != ARM_MATH_SUCCESS)
+        return rc;
+
+    arm_rfft_fast_f32(&fft_inst, in_buf, out_buf, 0);
+
+#define FMEAS_FFT_WINDOW_MIN_F 30.0f
+#define FMEAS_FFT_WINDOW_MAX_F 70.0f
+    const float binsize = (float)FMEAS_ADC_SAMPLING_RATE / FMEAS_FFT_LEN;
+    const int first_bin = (int)(FMEAS_FFT_WINDOW_MIN_F / binsize);
+    const int last_bin = (int)(FMEAS_FFT_WINDOW_MAX_F / binsize + 0.5f);
+    const int nbins = last_bin - first_bin + 1;
+
+    /* Copy real values of target data to front of output buffer */
+    for (size_t i=0; i<nbins; i++)
+        out_buf[i] = out_buf[2 * (first_bin + i)];
+
+    LMstat lmstat;
+    levmarq_init(&lmstat);
+
+    float a_max = 0.0f;
+    int i_max = 0;
+    for (size_t i=0; i<nbins; i++) {
+        if (out_buf[i] > a_max) {
+            a_max = out_buf[i];
+            i_max = i;
+        }
+    }
+
+    float par[3] = {
+        a_max, i_max, 1.0f
+    };
+
+    if (levmarq(3, &params, nbins, out_buf, NULL, func_gauss, func_gauss_grad, NULL, &lmstat))
+        return -1;
+
+    *out = (params[1] + first_bin) * binsize;
+
+    return 0;
+}
+
+float func_gauss(float *params, int x, void *userdata) {
+    UNUSED(userdata);
+    float a = params[0];
+    float mu = params[1];
+    float sigma = params[2];
+    return a*expf(-arm_power_f32((x-mu), 2.0f/(2.0f*(sigma*sigma))));
+}
+
+float func_gauss_grad(float *out, float *params, int x, void *userdata) {
+    UNUSED(userdata);
+    float a = params[0];
+    float mu = params[1];
+    float sigma = params[2];
+    return -(x-mu) / (  sigma*sigma*sigma * 2.5066282746310002f) * a*expf(-arm_power_f32((x-mu), 2.0f/(2.0f*(sigma*sigma))));
+}