decoder seems to be working, but encoder looks a bit borked.

1 files changed, 47 insertions, 118 deletions

diff --git a/center_fw/src/main.c b/center_fw/src/main.c
index 4df1db5..53b6aae 100644
--- a/center_fw/src/main.c
+++ b/center_fw/src/main.c
@@ -16,10 +16,10 @@
  */
 
 #include "global.h"
+#include "8b10b.h"
 
-uint16_t adc_data[192*2];
-
-const int nominal_period = 125*16*32/2;
+static uint16_t adc_data[64*2];
+static volatile struct state_8b10b_dec st_8b10b_dec;
 
 static void quicksort(uint16_t *head, uint16_t *tail);
 
@@ -64,11 +64,13 @@ int main(void) {
     NVIC_SetPriority(TIM1_CC_IRQn, 0);
     */
 
+    xfr_8b10b_reset((struct state_8b10b_dec *)&st_8b10b_dec);
+
     TIM3->CR1 = TIM_CR1_ARPE;
     TIM3->CR2 = (2<<TIM_CR2_MMS_Pos); /* Update event on TRGO */
     TIM3->PSC = 0;
     /* We sample 32 times per 1 kHz AC cycle, and use 32 times oversampling. */
-    TIM3->ARR = 125*32; /* Output 64 MHz / 125 = 512 kHz signal */
+    TIM3->ARR = 125*16; /* Output 64 MHz / 125 = 512 kHz signal */
     TIM3->CR1 |= TIM_CR1_CEN;
     
     DMAMUX1[0].CCR = 5; /* ADC */
@@ -121,131 +123,58 @@ void TIM1_CC_IRQHandler(void) {
     TIM1->SR &= ~TIM_SR_CC1IF;
 }
 */
+static size_t received_symbols = 0;
+static int symbol_buf[32];
+static size_t received_bits = 0;
+static int16_t bit_buf[256];
+size_t adc_reduced_pos = 0;
+static uint8_t adc_reduced[4096];
 
 void DMA1_Channel1_IRQHandler(void) {
-    static int32_t bottom = -1;
-    static int32_t top = -1;
+    static int sampling_phase = 0;
+    static int last_sample = 0;
+
+    uint16_t *buf = (DMA1->ISR & DMA_ISR_HTIF1) ? &adc_data[0] : &adc_data[COUNT_OF(adc_data)/2];
     DMA1->IFCR = DMA_IFCR_CGIF1;
-    int phase_correction = 0;
     GPIOB->BSRR = (1<<7);
-    uint16_t *data = DMA1->ISR & DMA_ISR_HTIF1 ? &adc_data[0] : &adc_data[192];
-
-    if (bottom >= 0) {
-        uint32_t amplitude = top - bottom;
-        uint32_t middle = bottom + amplitude / 2;
-
-        const uint32_t lower_thr = bottom + amplitude / 4;
-        const uint32_t upper_thr = top - amplitude / 4;
-        const uint32_t adc_clockdiv = 125 * 32;
-
-        int num_edges = 0;
-        int edge_indices[24];
-
-        int state = 0;
-        ssize_t run_start = -1;
-        int last_v = -1;
-        for (ssize_t i=0; i<192-1; i++) {
-            uint32_t a = data[i], b = data[i+1];
-
-            if (state == 0) {
-                if (a < lower_thr && b > lower_thr) {
-                    state = 1;
-                    run_start = i+1;
-                } else if (a > upper_thr && b < upper_thr) {
-                    state = -1;
-                    run_start = i+1;
-                }
-
-            } else if (state == 1) {
-                if (b < a) {
-                    state = 0;
-                } else if (a < upper_thr && b > upper_thr) {
-                    /* run from run_start (incl.) to i (incl.) */
-                    uint32_t v0 = data[run_start];
-                    int d = a - v0;
-                    int c = i - run_start;
-                    size_t intercept = run_start * adc_clockdiv + (middle - v0) * adc_clockdiv * c / d;
-                    if (num_edges < COUNT_OF(edge_indices)) {
-                        edge_indices[num_edges] = intercept;
-                        num_edges++;
-                    }
-                    state = 0;
-                }
-
-            } else if (state == -1) {
-                if (b > a) {
-                    state = 0;
-                } else if (a > lower_thr && b < lower_thr) {
-                    uint32_t v0 = data[run_start];
-                    int d = a - v0;
-                    int c = i - run_start;
-                    size_t intercept = run_start * adc_clockdiv + (middle - v0) * adc_clockdiv * c / d;
-                    if (num_edges < COUNT_OF(edge_indices)) {
-                        edge_indices[num_edges] = intercept;
-                        num_edges++;
-                    }
-                    state = 0;
-                }
-            }
+
+    const int threshold_adc_counts = 28500;
+    const int sample_per_baud = 16;
+
+    for (size_t i=0; i<COUNT_OF(adc_data)/2; i++) {
+        int sample = buf[i];
+
+        adc_reduced[adc_reduced_pos] = (sample & 0xffff)>>9;
+        if (adc_reduced_pos == 0) {
+            asm volatile ("bkpt");
         }
 
-        if (num_edges > 1) {
-            const int approx_cycle = 32*16*125/2;
-            int delta_avg = 0;
-            for (size_t i=0; i<num_edges-1; i++) {
-                int delta = edge_indices[i+1] - edge_indices[i];
-                if (delta > approx_cycle/2 * 50) {
-                    asm volatile ("bkpt");
-                }
-                while (delta > approx_cycle/2) {
-                    delta -= approx_cycle;
-                }
-                delta_avg += delta;
-            }
-            delta_avg /= num_edges-1;
-
-            int cycle = approx_cycle + delta_avg;
-            int offset = 0;
-            int phase_avg = 0;
-            for (size_t i=0; i<num_edges; i++) {
-                int remainder = edge_indices[i] - offset;
-                while (remainder > cycle/2) {
-                    remainder -= cycle;
-                    offset += cycle;
-                }
-                phase_avg += remainder;
-            }
-            phase_avg /= num_edges;
-            phase_correction = phase_avg >= 0 ? cycle/2 - phase_avg : cycle/2 + phase_avg;
-            phase_correction /= 125 * 4;
-
-            const int deadzone = 3;
-            const int max_correction = 40;
-            if (phase_correction < -deadzone || phase_correction > deadzone) {
-                if (phase_correction < -max_correction) {
-                    phase_correction = -max_correction;
-                } else if (phase_correction > max_correction) {
-                    phase_correction = max_correction;
-                }
+        if ((last_sample <= threshold_adc_counts && sample >= threshold_adc_counts) ||
+            (last_sample >= threshold_adc_counts && sample <= threshold_adc_counts)){
+            sampling_phase = sample_per_baud / 4; /* /2 for half baud sampling point, /2 for sinusoidal edge shape */
+
+        } else if (sampling_phase == 0) {
+            int bit = sample < threshold_adc_counts;
+            adc_reduced[adc_reduced_pos] |= 0x80;
+
+            bit_buf[received_bits] = bit;
+            received_bits = (received_bits+1) % COUNT_OF(bit_buf);
+
+            int rc =  xfr_8b10b_feed_bit((struct state_8b10b_dec *)&st_8b10b_dec, bit);
+            if (rc > -K_CODES_LAST) {
+                symbol_buf[received_symbols] = rc;
+                received_symbols = (received_symbols+1) % COUNT_OF(symbol_buf);
             }
-        }
-    }
+            sampling_phase = sample_per_baud;
 
-    const int discard = 5;
-    const int keep = 32;
+        } else {
+            sampling_phase--;
+        }
 
-    bottom = 0;
-    top = 0;
-    quicksort(data, &data[192-1]);
-    for (size_t i=0; i<keep; i++) {
-        bottom += data[discard + i];
-        top += data[COUNT_OF(data)/2 - 1 - discard - i];
+        adc_reduced_pos = (adc_reduced_pos+1) % COUNT_OF(adc_reduced);
+        last_sample = sample;
     }
 
-    bottom /= keep;
-    top /= keep;
-
-    TIM3->ARR = 125*32 + phase_correction; 
     GPIOB->BRR = (1<<7);
 }