feat: add live statistics with per-trial snapshots and von Neumann option (FPGA v5)

arduino/strix_capture/strix_capture.ino

@@ -7,6 +7,7 @@
 //   w <register> <value>  write a register, prints "OK"
 //   cap                   start a capture with the current settings and send it as
 //                         "DATA <n>\n" followed by n raw bytes
+//   stats                 print the latest statistics trial snapshot as hex
 
 #include <SPI.h>
 #include <VidorBoot.h>
@@ -23,6 +24,7 @@ enum : uint8_t {
   REG_CONTROL = 0x0B,
   REG_STATUS = 0x0C,
   REG_DATA = 0x10,
+  REG_STATS = 0x40,
 };
 
 const uint8_t READ = 0x80;
@@ -30,6 +32,7 @@ const uint8_t CONTROL_START_CAPTURE = 0x01;
 const uint8_t STATUS_CAPTURE_DONE = 0x02;
 const size_t CAPTURE_BYTES = 32768;
 const size_t CHUNK_BYTES = 512;
+const size_t SNAPSHOT_BYTES = 72;
 
 VidorUtils fpga;
 
@@ -89,6 +92,17 @@ void capture() {
   }
 }
 
+void printSnapshot() {
+  beginTransaction(READ | REG_STATS);
+  for (size_t i = 0; i < SNAPSHOT_BYTES; i++) {
+    uint8_t value = strixSpi.transfer(0);
+    if (value < 0x10) Serial.print('0');
+    Serial.print(value, HEX);
+  }
+  endTransaction();
+  Serial.println();
+}
+
 // Parses "<a>" or "<a> <b>" after the command word; returns the number of values found.
 int parseArgs(const String &args, long &a, long &b) {
   int space = args.indexOf(' ');
@@ -116,6 +130,8 @@ void handleCommand(String line) {
     Serial.println("OK");
   } else if (command == "cap") {
     capture();
+  } else if (command == "stats") {
+    printSnapshot();
   } else if (line.length() > 0) {
     Serial.println("ERR unknown or malformed command");
   }