detect preamble in sniffer code

CommandStation-EX.ino

@@ -51,6 +51,8 @@
 
 #include "DCCEX.h"
 #include "Display_Implementation.h"
+#include "Sniffer.h"
+Sniffer *DCCSniffer = NULL;
 
 #ifdef CPU_TYPE_ERROR
 #error CANNOT COMPILE - DCC++ EX ONLY WORKS WITH THE ARCHITECTURES LISTED IN defines.h
@@ -124,6 +126,7 @@ void setup()
   // Start RMFT aka EX-RAIL (ignored if no automnation)
   RMFT::begin();
 
+  DCCSniffer = new Sniffer(16);
 
   // Invoke any DCC++EX commands in the form "SETUP("xxxx");"" found in optional file mySetup.h.
   //  This can be used to create turnouts, outputs, sensors etc. through the normal text commands.
@@ -158,8 +161,27 @@ void looptimer(unsigned long timeout, const FSH* message)
   lasttimestamp = now;
 }
 *********************************************/
+void loopdiag(unsigned long timeout)
+{
+  static unsigned long lasttimestamp = 0;
+  unsigned long now = millis();
+  if (timeout != 0) {
+    unsigned long diff = now - lasttimestamp;
+    if (diff > timeout) {
+      if (DCCSniffer)
+	DIAG(F("ticks=%L"), DCCSniffer->getTicks());
+      lasttimestamp = millis();
+      return;
+    }
+  }
+//  lasttimestamp = now;
+}
 void loop()
 {
+  // Some debug for sniffer code
+  //  loopdiag(937); // Do not use a value that does divide even in 80Mhz ticks
+  digitalWrite(2,LOW);
+
   // The main sketch has responsibilities during loop()
 
   // Responsibility 1: Handle DCC background processes

Sniffer.cpp

@@ -1,10 +1,78 @@
 #ifdef ARDUINO_ARCH_ESP32
-#include Sniffer.h
+#include "Sniffer.h"
+#include "DIAG.h"
+//extern Sniffer *DCCSniffer;
+
+static bool IRAM_ATTR cap_ISR_cb(mcpwm_unit_t mcpwm, mcpwm_capture_channel_id_t cap_channel, const cap_event_data_t *edata,void *user_data) {
+  if (edata->cap_edge == MCPWM_BOTH_EDGE) {
+    // should not happen at all
+    // delays here might crash sketch
+    for (int n=0 ; n<10; n++) {
+      digitalWrite(2,HIGH);
+      delay(500);
+      digitalWrite(2,LOW);
+      delay(500);
+    }
+    return 0;
+  }
+  if (user_data) ((Sniffer *)user_data)->processInterrupt(edata->cap_value, edata->cap_edge == MCPWM_POS_EDGE);
+//if (DCCSniffer)            DCCSniffer->processInterrupt(edata->cap_value, edata->cap_edge == MCPWM_POS_EDGE);
+
+  return 0;
+}
+
 Sniffer::Sniffer(byte snifferpin) {
   mcpwm_gpio_init(MCPWM_UNIT_0, MCPWM_CAP_0, snifferpin);
+  // set capture edge, BIT(0) - negative edge, BIT(1) - positive edge
+  // MCPWM_POS_EDGE|MCPWM_NEG_EDGE should be 3.
+  //mcpwm_capture_enable(MCPWM_UNIT_0, MCPWM_SELECT_CAP0, MCPWM_POS_EDGE|MCPWM_NEG_EDGE, 0);
+  //mcpwm_isr_register(MCPWM_UNIT_0, sniffer_isr_handler, NULL, ESP_INTR_FLAG_IRAM, NULL);
+  //MCPWM0.int_ena.cap0_int_ena = 1;                      // Enable interrupt on CAP0 signal
+
+  mcpwm_capture_config_t MCPWM_cap_config = { //Capture channel configuration
+    .cap_edge = MCPWM_BOTH_EDGE,              // according to mcpwm.h
+    .cap_prescale = 1,                        // 1 to 256 (see .h file)
+    .capture_cb = cap_ISR_cb,                 // user defined ISR/callback
+    .user_data = (void *)this                 // user defined argument to callback
+  };
+  pinMode(2 ,OUTPUT);
+  digitalWrite(2,LOW);
+  ESP_ERROR_CHECK(mcpwm_capture_enable_channel(MCPWM_UNIT_0, MCPWM_SELECT_CAP0, &MCPWM_cap_config));
+}
+
+#define DCC_TOO_SHORT 4000L // 4000 ticks are 50usec
+#define DCC_ONE_LIMIT 6400L // 6400 ticks are 80usec
+
+void IRAM_ATTR Sniffer::processInterrupt(int32_t capticks, bool posedge) {
+  bool bit = 0;
+  diffticks = capticks - lastticks;
+  if (lastedge != posedge) {
+    if (diffticks < DCC_TOO_SHORT) {
+      return;
+    }
+    if (diffticks < DCC_ONE_LIMIT) {
+      bit = 1;
+    } else {
+      bit = 0;
+    }
+    lastticks = capticks;
+    lastedge = posedge;
+    bitfield = bitfield << 1;
+    bitfield = bitfield + bit;
+    if ((bitfield & 0xFFFFFF) == 0xFFFFFC){
+      // This detects the 24 last halfbits
+      // which 22 are ONE and 2 are ZERO
+      // so preabmle of 11 ONES and one ZERO
+      digitalWrite(2,HIGH);
+    }
+  }
+//  if (ticks > 800000000) //10sec
+//    DIAG(F("tick"));
+}
+
+/*
+static void IRAM_ATTR sniffer_isr_handler(void *) {
+  DCCSniffer.processInterrupt();
 }
-#endif
-#include <Arduino.h>
-#include "driver/mcpwm.h"
-#include "soc/mcpwm_struct.h"
-#include "soc/mcpwm_reg.h"
+*/
+#endif // ESP32

Sniffer.h

@@ -7,6 +7,17 @@
 class Sniffer {
 public:
   Sniffer(byte snifferpin);
+  void IRAM_ATTR processInterrupt(int32_t capticks, bool posedge);
+  inline int32_t getTicks() {
+    noInterrupts();
+    int32_t i = diffticks;
+    interrupts();
+    return i;
+  };
 private:
-}
+  int64_t bitfield = 0;
+  int32_t diffticks;
+  int32_t lastticks;
+  bool lastedge;
+};
 #endif