Add basic support for shift-register handling

defines.h

@@ -168,6 +168,8 @@ struct ServoData {
 #define EXIOINITA 0xE8    // Flag to send analogue pin info
 #define EXIOPINS 0xE9     // Flag we need to send pin counts
 #define EXIOWRAN 0xEA     // Flag we're receiving an analogue write (PWM)
+#define EXIOSHIFTIN  0xEB
+#define EXIOSHIFTOUT 0xEC
 #define EXIOERR 0xEF      // Flag something has errored to send to device driver
 
 /////////////////////////////////////////////////////////////////////////////////////

i2c_functions.cpp

@@ -23,27 +23,32 @@
 #include "i2c_functions.h"
 #include "display_functions.h"
 #include "pin_io_functions.h"
+#include "shiftio_functions.h"
 
 uint8_t numAnaloguePins = 0;  // Init with 0, will be overridden by config
 uint8_t numDigitalPins = 0;   // Init with 0, will be overridden by config
 uint8_t numPWMPins = 0;  // Number of PWM capable pins
 bool setupComplete = false;   // Flag when initial configuration/setup has been received
 uint8_t outboundFlag;   // Used to determine what data to send back to the CommandStation
 byte commandBuffer[3];    // Command buffer to interact with device driver
-byte responseBuffer[1];   // Buffer to send single response back to device driver
 uint8_t numReceivedPins = 0;
 
+static const uint8_t EXIO_SHIFT_MAX_BYTES = 16;   // up to 16 bytes (128 bits) safely under I2C 32-byte limit
+byte responseBuffer[1 + EXIO_SHIFT_MAX_BYTES];    // [status][payload...]
+uint8_t responseLength = 0;
+
 /*
 * Function triggered when CommandStation is sending data to this device.
 */
 void receiveEvent(int numBytes) {
-  if (numBytes == 0) {
-    return;
-  }
-  byte buffer[numBytes];
-  for (uint8_t byte = 0; byte < numBytes; byte++) {
-    buffer[byte] = Wire.read();   // Read all received bytes into our buffer array
+  if (numBytes <= 0) return;
+
+  byte buffer[32];
+  if (numBytes > 32) numBytes = 32;
+  for (uint8_t i = 0; i < numBytes; i++) {
+    buffer[i] = Wire.read();
   }
+
   switch(buffer[0]) {
     // Initial configuration start, must be 2 bytes
     case EXIOINIT:
@@ -151,6 +156,76 @@ void receiveEvent(int numBytes) {
         responseBuffer[0] = EXIOERR;
       }
       break;
+    case EXIOSHIFTIN: {
+      outboundFlag = EXIOSHIFTIN;
+
+      // Payload: [cmd][clkPin][latchPin][dataPin][nBytes]
+      if (numBytes != 5) {
+        responseBuffer[0] = EXIOERR;
+        responseLength = 1;
+        break;
+      }
+
+      uint8_t clk   = buffer[1];
+      uint8_t latch = buffer[2];
+      uint8_t data  = buffer[3];
+      uint8_t n     = buffer[4];
+
+      USB_SERIAL.print("SHIFTIN clk=");
+      USB_SERIAL.print(clk);
+      USB_SERIAL.print(" latch=");
+      USB_SERIAL.print(latch);
+      USB_SERIAL.print(" data=");
+      USB_SERIAL.print(data);
+      USB_SERIAL.print(" n=");
+      USB_SERIAL.println(n);
+
+      if (n == 0 || n > EXIO_SHIFT_MAX_BYTES) {
+        responseBuffer[0] = EXIOERR;
+        responseLength = 1;
+        break;
+      }
+
+      responseBuffer[0] = EXIORDY;
+      exioShiftInBytes(clk, latch, data, &responseBuffer[1], n);
+
+      responseLength = 1 + n;
+      break;
+    }
+
+    case EXIOSHIFTOUT: {
+      outboundFlag = EXIOSHIFTOUT;
+
+      // Payload: [cmd][clkPin][latchPin][dataPin][nBytes][byte0..byteN-1]
+      if (numBytes < 6) {
+        responseBuffer[0] = EXIOERR;
+        responseLength = 1;
+        break;
+      }
+
+      uint8_t clk   = buffer[1];
+      uint8_t latch = buffer[2];
+      uint8_t data  = buffer[3];
+      uint8_t n     = buffer[4];
+
+      if (n == 0 || n > EXIO_SHIFT_MAX_BYTES) {
+        responseBuffer[0] = EXIOERR;
+        responseLength = 1;
+        break;
+      }
+
+      if (numBytes != (5 + n)) {
+        responseBuffer[0] = EXIOERR;
+        responseLength = 1;
+        break;
+      }
+
+      exioShiftOutBytes(clk, latch, data, &buffer[5], n);
+
+      responseBuffer[0] = EXIORDY;
+      responseLength = 1;
+      break;
+    }
     default:
       break;
   }
@@ -197,6 +272,10 @@ void requestEvent() {
     case EXIOWRD:
       Wire.write(responseBuffer, 1);
       break;
+    case EXIOSHIFTIN:
+    case EXIOSHIFTOUT:
+      Wire.write(responseBuffer, responseLength);
+      break;
     default:
       break;
   }

shiftio_functions.cpp

@@ -0,0 +1,84 @@
+#include <Arduino.h>
+#include "shiftio_functions.h"
+#include "globals.h"   // pinMap[], pinNameMap[], numPins
+
+static bool mapPins(uint8_t clk, uint8_t latch, uint8_t data,
+                    uint8_t &pClk, uint8_t &pLatch, uint8_t &pData) {
+  if (clk >= numPins || latch >= numPins || data >= numPins) return false;
+  pClk   = pinMap[clk].physicalPin;
+  pLatch = pinMap[latch].physicalPin;
+  pData  = pinMap[data].physicalPin;
+  return true;
+}
+
+static uint8_t shiftInByte_phys(uint8_t pClk, uint8_t pLatch, uint8_t pData) {
+  uint8_t value = 0;
+
+  digitalWrite(pLatch, HIGH);
+  delayMicroseconds(1);
+  digitalWrite(pLatch, LOW);
+
+  for (int i = 0; i < 8; i++) {
+    digitalWrite(pClk, LOW);
+    delayMicroseconds(1);
+
+    if (digitalRead(pData)) value |= (1 << (7 - i));
+
+    digitalWrite(pClk, HIGH);
+    delayMicroseconds(1);
+  }
+  return value;
+}
+
+static void shiftOutByte_phys(uint8_t pClk, uint8_t pData, uint8_t value) {
+  for (int i = 7; i >= 0; i--) {
+    digitalWrite(pData, (value >> i) & 0x01);
+    digitalWrite(pClk, HIGH);
+    delayMicroseconds(1);
+    digitalWrite(pClk, LOW);
+  }
+}
+
+void exioShiftInBytes(uint8_t clk, uint8_t latch, uint8_t data, uint8_t* out, uint8_t nBytes) {
+  uint8_t pClk, pLatch, pData;
+  if (!mapPins(clk, latch, data, pClk, pLatch, pData)) {
+    // fail-safe: return all 0xFF so you can spot it (or all 0x00, your choice)
+    for (uint8_t i = 0; i < nBytes; i++) out[i] = 0xFF;
+    return;
+  }
+
+  pinMode(pClk, OUTPUT);
+  pinMode(pLatch, OUTPUT);
+  pinMode(pData, INPUT_PULLUP);
+  digitalWrite(pClk, LOW);
+  digitalWrite(pLatch, LOW);
+
+  USB_SERIAL.print(F("SHIFTIN idx "));
+  USB_SERIAL.print(clk); USB_SERIAL.print("/");
+  USB_SERIAL.print(latch); USB_SERIAL.print("/");
+  USB_SERIAL.print(data); USB_SERIAL.print(F(" => phys "));
+  USB_SERIAL.print(pClk); USB_SERIAL.print("/");
+  USB_SERIAL.print(pLatch); USB_SERIAL.print("/");
+  USB_SERIAL.println(pData);
+
+  for (uint8_t i = 0; i < nBytes; i++) {
+    out[i] = shiftInByte_phys(pClk, pLatch, pData);
+  }
+}
+
+void exioShiftOutBytes(uint8_t clk, uint8_t latch, uint8_t data, const uint8_t* in, uint8_t nBytes) {
+  uint8_t pClk, pLatch, pData;
+  if (!mapPins(clk, latch, data, pClk, pLatch, pData)) return;
+
+  pinMode(pClk, OUTPUT);
+  pinMode(pLatch, OUTPUT);
+  pinMode(pData, OUTPUT);
+  digitalWrite(pClk, LOW);
+  digitalWrite(pLatch, LOW);
+
+  for (int i = (int)nBytes - 1; i >= 0; i--) {
+    shiftOutByte_phys(pClk, pData, in[i]);
+  }
+
+  digitalWrite(pLatch, HIGH);
+}

shiftio_functions.h

@@ -0,0 +1,5 @@
+#pragma once
+#include <Arduino.h>
+
+void exioShiftInBytes(uint8_t clk, uint8_t latch, uint8_t data, uint8_t* out, uint8_t nBytes);
+void exioShiftOutBytes(uint8_t clk, uint8_t latch, uint8_t data, const uint8_t* in, uint8_t nBytes);