created two new C functions that can be accessed from the python layer

lib/cionic/emg_iir.c

@@ -15,6 +15,10 @@ float emg_lowpass_filter_sos[NO_OF_BQS][NO_OF_COEFFS_PER_BQ] = {
     {1.0,2.0,1.0,1.0,-1.4083885078365557,0.7369080185138834},
 };
 
+static uint8_t g_emg_sub_sampling_rate = 1;   
+static uint16_t g_ma_size = EMG_RMS_MA_SIZE;   
+
+
 // takes as input a bank of biquad coefficients ( NO_OF_BQS of them ) with the
 // order of the coefficients as shown below. conveniently, this is the same
 // order of the SOS ( second order section ) coefficients as produced by the
@@ -80,12 +84,12 @@ emg_mwa_rms(emg_mwa_state_t *state, float val)
     state->sum -= state->mw[state->write_ptr];    
     // update the delay line
     state->mw[state->write_ptr] = val*val;    
-    state->write_ptr = (state->write_ptr+1) % EMG_RMS_MA_SIZE;
+    state->write_ptr = (state->write_ptr+1) % g_ma_size;
 
     // the latest sum
     state->sum += val*val;
     double result = state->sum;
-    result = sqrt(result/EMG_RMS_MA_SIZE);
+    result = sqrt(result/g_ma_size);
 #ifdef EMG_RMS_DC_BLOCKING
     result = result + state->dc; 
     state->dc = state->dc - result*state->alpha;
@@ -101,7 +105,8 @@ emg_mwa_rms(emg_mwa_state_t *state, float val)
 void
 iir_filter_init(iir_filter_t *filter)
 {
-    filter->emg_rms_sub_sample_counter = EMG_RMS_SUBSAMPLING_FACTOR;
+    filter->emg_rms_sub_sample_counter = g_emg_sub_sampling_rate;
+    g_ma_size = EMG_RMS_MA_SIZE/g_emg_sub_sampling_rate;
     for( int i=0; i<IIR_NUM_CHANNELS; i++) {
         emg_iir_init(&filter->emg_lowpass_iir_state[i]);
         emg_iir_init(&filter->emg_highpass_iir_state[i]);
@@ -140,9 +145,44 @@ iir_filter_process(iir_filter_t *filter, float *norms, int numchans,
     if (filter->emg_rms_sub_sample_counter <= 0)
     {
         *ts_out = ts_in;
-        filter->emg_rms_sub_sample_counter = EMG_RMS_SUBSAMPLING_FACTOR;
+        filter->emg_rms_sub_sample_counter = g_emg_sub_sampling_rate;
         return 0;
     }
 
     return -1;
 }
+
+void set_emg_filter(mp_obj_t coeffs_list, mp_obj_t low) 
+{
+
+    size_t array_size = 0;
+    mp_obj_t *values;
+    mp_obj_get_array(coeffs_list, &array_size, &values);
+
+
+    float (*emg_filter)[NO_OF_COEFFS_PER_BQ];
+
+    if (low == mp_const_true) {
+        emg_filter = emg_lowpass_filter_sos;
+        mp_printf(&mp_plat_print, "setting the low pass filter bank \n");
+    } else {
+        emg_filter = emg_highpass_filter_sos;
+        mp_printf(&mp_plat_print, "setting the high pass filter bank \n");
+    }
+
+    for (int i = 0; i < NO_OF_BQS; i++) {
+        mp_printf(&mp_plat_print, "------------------------\n");
+        mp_printf(&mp_plat_print, "bank %d:\n", i);
+        for (int j = 0; j < NO_OF_COEFFS_PER_BQ; j++) {
+            emg_filter[i][j] = mp_obj_get_float(values[i*NO_OF_COEFFS_PER_BQ+j]);
+            mp_printf(&mp_plat_print, "c[%d][%d]: %f;", i, j, (double) emg_filter[i][j]);
+        }
+        mp_printf(&mp_plat_print, "\n");
+    }
+}
+
+void set_emg_decim_rate(mp_obj_t decim_rate)
+{
+    g_emg_sub_sampling_rate =  mp_obj_get_int(decim_rate); 
+    mp_printf(&mp_plat_print, "emg decimation rate set to: %d\n", g_emg_sub_sampling_rate);
+}

lib/cionic/emg_iir.h

@@ -12,8 +12,9 @@
 #define EMG_RMS_FILTER_ORDER (6)
 #define EMG_RMS_HIGHPASS_FC (50)
 #define EMG_RMS_LOWPASS_FC (199)
-#define EMG_RMS_SUBSAMPLING_FACTOR (5)  
-#define EMG_RMS_MA_SIZE (300/(EMG_RMS_SUBSAMPLING_FACTOR))
+// #define EMG_RMS_SUBSAMPLING_FACTOR (5)  
+// #define EMG_RMS_MA_SIZE (300/(EMG_RMS_SUBSAMPLING_FACTOR))
+#define EMG_RMS_MA_SIZE (256)   // maximum size
 #define EMG_RMS_MA_DC_BLOCK_FC (0.001)
 #define EMG_RMS_MA_DC_BLOCK_ALPHA (2*M_PI*EMG_RMS_MA_DC_BLOCK_FC/EMG_RMS_FS)
 
@@ -35,7 +36,7 @@ typedef struct emg_mwa_state {
 } emg_mwa_state_t;
 
 typedef struct iir_filter_t {
-    int emg_rms_sub_sample_counter;
+    uint8_t emg_rms_sub_sample_counter;
     emg_filter_state_t emg_lowpass_iir_state[IIR_NUM_CHANNELS]; 
     emg_filter_state_t emg_highpass_iir_state[IIR_NUM_CHANNELS]; 
     emg_mwa_state_t emg_mwa_state[IIR_NUM_CHANNELS];
@@ -51,5 +52,10 @@ int iir_filter_process(iir_filter_t *filter, float *norms, int numchans,
                         elapsed_t ts_in, const uint8_t *buffer,
                         elapsed_t *ts_out, float *uv_out);
 
+// generated coefficients
+extern float emg_highpass_filter_sos[NO_OF_BQS][NO_OF_COEFFS_PER_BQ];
+extern float emg_lowpass_filter_sos[NO_OF_BQS][NO_OF_COEFFS_PER_BQ];
+void set_emg_filter(mp_obj_t coeffs_list, mp_obj_t low);
+void set_emg_decim_rate(mp_obj_t decim_rate);
 
 #endif //_EMG_IIR_H_

shared-bindings/ads1x9x/ADS1x9x.c

@@ -36,6 +36,7 @@
 #include "shared-bindings/busio/SPI.h"
 #include "shared-bindings/microcontroller/Pin.h"
 #include "supervisor/flash.h"
+#include "lib/cionic/emg_iir.h"
 
 //| class ADS1x9x:
 //|     """ADS1x9x Interface
@@ -217,10 +218,26 @@ STATIC mp_obj_t ads1x9x_ads1x9x_deinit(mp_obj_t self_in) {
 }
 MP_DEFINE_CONST_FUN_OBJ_1(ads1x9x_ads1x9x_deinit_obj, ads1x9x_ads1x9x_deinit);
 
+STATIC mp_obj_t ads1x9x_ads1x9x_set_emg_filter(mp_obj_t self_in, mp_obj_t coeffs_list, mp_obj_t low) {
+    set_emg_filter(coeffs_list, low);
+    return mp_const_none;
+}
+
+MP_DEFINE_CONST_FUN_OBJ_3(ads1x9x_ads1x9x_set_emg_filter_obj, ads1x9x_ads1x9x_set_emg_filter);
+
+STATIC mp_obj_t ads1x9x_ads1x9x_set_emg_decim_rate(mp_obj_t self_in, mp_obj_t decim_rate) {
+    set_emg_decim_rate(decim_rate);
+    return mp_const_none;
+}
+
+MP_DEFINE_CONST_FUN_OBJ_2(ads1x9x_ads1x9x_set_emg_decim_rate_obj, ads1x9x_ads1x9x_set_emg_decim_rate);
+
 STATIC const mp_rom_map_elem_t ads1x9x_ads1x9x_locals_dict_table[] = {
     { MP_ROM_QSTR(MP_QSTR_reset), MP_ROM_PTR(&ads1x9x_ads1x9x_reset_obj) },
     { MP_ROM_QSTR(MP_QSTR_sample_size_get), MP_ROM_PTR(&ads1x9x_ads1x9x_sample_size_get_obj) },
     { MP_ROM_QSTR(MP_QSTR_filter_set), MP_ROM_PTR(&ads1x9x_ads1x9x_filter_set_obj) },
+    { MP_ROM_QSTR(MP_QSTR_set_emg_filter), MP_ROM_PTR(&ads1x9x_ads1x9x_set_emg_filter_obj) },
+    { MP_ROM_QSTR(MP_QSTR_set_emg_decim_rate), MP_ROM_PTR(&ads1x9x_ads1x9x_set_emg_decim_rate_obj) },
     { MP_ROM_QSTR(MP_QSTR_read_reg), MP_ROM_PTR(&ads1x9x_ads1x9x_read_reg_obj) },
     { MP_ROM_QSTR(MP_QSTR_write_reg), MP_ROM_PTR(&ads1x9x_ads1x9x_write_reg_obj) },
     { MP_ROM_QSTR(MP_QSTR_start), MP_ROM_PTR(&ads1x9x_ads1x9x_start_obj) },

shared-module/ads1x9x/ADS1x9x.c

@@ -103,6 +103,7 @@ STATIC void ads129x_raw(ads1x9x_ADS1x9x_obj_t *self, uint8_t *in, float *out)
     int16_t ads_sample;
 
     for(i = 0 ; i < ADS1X9X_NUM_CHAN ; i++){
+        // int16_t, not int24_t?
         ads_sample = READ_BE(int16_t, in);
         out[i] = (float)ads_sample * self->all_norms[i];
         in += 2;