add DSP demos

Author: timchinowsky

ports/raspberrypi/common-hal/rp2pio/StateMachine.c

@@ -1428,9 +1428,48 @@ mp_obj_t common_hal_rp2pio_statemachine_get_last_write(rp2pio_statemachine_obj_t
 
 bool common_hal_rp2pio_statemachine_process(rp2pio_statemachine_obj_t *self, uint8_t stride_in_bytes,
     sm_buf_info *target_buf_info, sm_buf_info *parameters_buf_info, sm_buf_info *input_buf_info) {
-    for (void *i = target_buf_info->info.buf; i < target_buf_info->info.buf + (target_buf_info->info.len * stride_in_bytes); i += stride_in_bytes)
-    {};
-
+    if (parameters_buf_info->info.len > 2) {
+        if (stride_in_bytes == 2) {
+            int16_t op = ((int16_t *)parameters_buf_info->info.buf)[0];
+            int16_t *target;
+            target = (int16_t *)target_buf_info->info.buf;
+
+            switch (op) {
+                case 1: // multiply
+                    int16_t *factor;
+                    uint16_t *factor_index;
+                    size_t factor_samples;
+                    factor_samples = (parameters_buf_info->info.len - (2 * stride_in_bytes)) / stride_in_bytes;
+                    factor_index = ((uint16_t *)(parameters_buf_info->info.buf)) + 1;
+                    factor = ((int16_t *)(parameters_buf_info->info.buf)) + 2;
+                    for (size_t i = 0; i < (target_buf_info->info.len / stride_in_bytes); i++) {
+                        target[i] = ((int32_t)target[i] * (int32_t)factor[*factor_index]) >> 16;
+                        (*factor_index)++;
+                        if (*factor_index >= factor_samples) {
+                            *factor_index = 0;
+                        }
+                    }
+                    break;
+
+                case 2: // echo
+                    int16_t *memory;
+                    uint16_t *memory_index;
+                    size_t memory_samples;
+                    memory_samples = (parameters_buf_info->info.len - (2 * stride_in_bytes)) / stride_in_bytes;
+                    memory_index = ((uint16_t *)(parameters_buf_info->info.buf)) + 1;
+                    memory = ((int16_t *)(parameters_buf_info->info.buf)) + 2;
+                    for (size_t i = 0; i < (target_buf_info->info.len / stride_in_bytes); i++) {
+                        target[i] = (target[i] + (memory[*memory_index] >> 1)) >> 1; // fixed 50% decay for now
+                        memory[*memory_index] = target[i];
+                        (*memory_index)++;
+                        if (*memory_index >= memory_samples) {
+                            *memory_index = 0;
+                        }
+                    }
+                    break;
+            }
+        }
+    }
     return 1;
 }