unfuxed by flummoxing earle pio code

rp2040_uart/2024-03_rp2040-uart.md

@@ -61,9 +61,17 @@ Not totally sure, but I'm going to move on to try out Earle's software serial PI
 
 So - let's try this out. 
 
-OK, my big dawg `earle` looks to have this locked down, it is werken. It's also wrapped in the arduino Serial API meaning I could use 'em in an abstracted class for P2P comms. Bless his heart, now I need to check i.e. continuity and make some measurements... 
+OK, I have this up and running: I am streaming at a fixed BAUD, then counting the ratio of bytes we miss in a stream. The uc's are counting missed and proper bytes (reading monotonic sequence numbers) and then checking also intervals between transmissions... 
 
-Ah, jesus, nevermind, it is catching garbage bytes... all 255's, and it's reporting new-byteness when in fact none are visible on the line. 
+| Mbit/s | Misses (errs / total-bytes) | Expected Byte Time (us) | Avg Byte Time |
+| --- | --- | --- | --- |
+| 0.1 | nil | 100 | 110.2 |
+| 0.5 | nil | 20 | 22.2 | 
+| 1.0 | 0.025 (1/40) (!) | 10 | 13.4 |
+| 2.5 | 0.497 | 4 | 11.0 |
+| 5.0 | 0.755 | 2 | 11.0 |
+
+So, I'm not convinced that I haven't fuxd anything here... it seems wild that we would have such a bottleneck to performance, and there are a few red flags here; namely that we have a lower bound of 11us between transmits, which would also explain our increasing error rate when we surpass 1 Mbit/sec (as the byte-wise period there is 10us or so). 
 
 ---
 

rp2040_uart/code/uart_pio_earle_rx/uart_pio_earle_rx.ino → rp2040_uart/code/uart_pio_earle_tx_rx/uart_pio_earle_tx_rx.ino

@@ -6,11 +6,11 @@
 // "D10" - GPIO 3 
 #define PIN_DEBUG 3 
 
-// on XIAO "RX" - GPIO 1
 #define PIN_RX 1
-#define PIO_BAUD 1000000
+#define PIN_TX 0 
+#define PIO_BAUD 2500000
 
-SerialPIO serial(SerialPIO::NOPIN, PIN_RX);
+SerialPIO serial(PIN_TX, PIN_RX);
 
 void setup(void){
   pinMode(PIN_LED_B, OUTPUT);
@@ -27,39 +27,70 @@ void setup(void){
 }
 
 uint32_t lastUpdate = 0;
-uint32_t updateInterval = 200;
+uint32_t updateInterval = 1000;
 
 uint8_t expectedRx = 0;
 uint32_t missCount = 0;
 uint32_t catchCount = 0;
 
+uint8_t expected_miss = 0;
+uint8_t actual_miss = 0;
+
 uint8_t chars[256];
 
+uint8_t seqNum = 0;
+
+// and let's calculate actual bandwidth (success bytes / sec * 8) and bitrate ( * 10)
+// and record avg per-cycle pickup ? 
+
+uint32_t lastTx = 0;
+float intervalEstimate = 0.0F;
+
 void loop(void){
+
+  // catch 'em AFAP 
   if(serial.available()){
-    // earle core throws -1 if we have an error, 
+    while(serial.available()){
       int data = serial.read();
+      // earle core throws -1 if we have an error, 
       if(data < 0) {
         return;
       }
       // count total hits 
       catchCount ++;
-    // catch data and count sequence errors 
-    digitalWrite(PIN_DEBUG, !digitalRead(PIN_DEBUG));
+      // stuff it 
       chars[catchCount & 255] = data;
+      // check for missus 
       if(data != expectedRx){
+        actual_miss = data;
+        expected_miss = expectedRx;
         missCount ++;
       }
       expectedRx = data + 1;
     }
-  // uint8_t data = uart_rx_program_getc(pio, sm);
-  // digitalWrite(PIN_DEBUG, LOW);
+  }
+
+  // and write AFAP, recording outgoing times 
+  if(serial.availableForWrite()){
+    digitalWrite(PIN_DEBUG, !digitalRead(PIN_DEBUG));
+    serial.write(seqNum ++);
+    uint32_t txTime = micros();
+    uint32_t txInterval = txTime - lastTx;
+    lastTx = txTime;
+    intervalEstimate = (float)txInterval * 0.01F + intervalEstimate * 0.99F;
+    // while(serial.availableForWrite()){
+    // }
+  }
+
   // ... 
   if(lastUpdate + updateInterval < millis()){
     lastUpdate = millis();
     digitalWrite(PIN_LED_B, !digitalRead(PIN_LED_B));
     displayPrint(String(missCount) + " / " + String(catchCount) + " \n" + 
-    String(chars[0]) + ", " + String(chars[1]) + ", " + String(chars[2]) + ", " + String(chars[3]) + ", " + String(chars[4]) + ", " + String(chars[5]) + ", "
+    "miss: " + String((float)missCount / (float)catchCount, 9) + "\n" + 
+    String(expected_miss) + ": " + String(actual_miss) + "\n" +
+    "avg interval: " + String(intervalEstimate, 4)
+    // String(chars[0]) + ", " + String(chars[1]) + ", " + String(chars[2]) + ", " + String(chars[3]) + ", " + String(chars[4]) + ", " + String(chars[5]) + ", "
     );
 
     // displayPrint(spipi_print());