Arduino frameworks

- AltSoftSerial UART with WT61 IMU
- UART with Pi on TX0/RX0 (and USB)

arduino/main/comms.cpp

@@ -0,0 +1,70 @@
+#include "comms.h"
+
+// Pi communication uses hardware Serial (pins 0/1)
+// Baud rate - 115200 is reasonable for duplex with Pi
+static const long BAUD_RATE = 115200;
+
+// Command buffer
+static const int CMD_BUF_SIZE = 64;
+static char cmdBuf[CMD_BUF_SIZE];
+static int cmdIndex = 0;
+static bool cmdReady = false;
+
+// Connection tracking
+static unsigned long lastRxTime = 0;
+
+void comms_init() {
+  Serial.begin(BAUD_RATE);
+  cmdIndex = 0;
+  cmdReady = false;
+}
+
+bool comms_update() {
+  while (Serial.available()) {
+    char c = Serial.read();
+    lastRxTime = millis();
+
+    if (c == '\n' || c == '\r') {
+      if (cmdIndex > 0) {
+        cmdBuf[cmdIndex] = '\0';
+        cmdReady = true;
+        cmdIndex = 0;
+        return true;
+      }
+    } else if (cmdIndex < CMD_BUF_SIZE - 1) {
+      cmdBuf[cmdIndex++] = c;
+    }
+    // else: overflow, silently drop extra chars
+  }
+  return false;
+}
+
+void comms_send(const char* key, float value, int decimals) {
+  Serial.print(key);
+  Serial.print(": ");
+  Serial.println(value, decimals);
+}
+
+void comms_send(const char* key, int value) {
+  Serial.print(key);
+  Serial.print(": ");
+  Serial.println(value);
+}
+
+void comms_send(const char* key, const char* value) {
+  Serial.print(key);
+  Serial.print(": ");
+  Serial.println(value);
+}
+
+const char* comms_get_command() {
+  if (cmdReady) {
+    cmdReady = false;
+    return cmdBuf;
+  }
+  return "";
+}
+
+bool comms_is_connected(unsigned long timeout_ms) {
+  return (millis() - lastRxTime) < timeout_ms;
+}