Added a reset command to interrupt long running operations.

Author: erikvanzijst

arduino/arduino.ino

@@ -16,13 +16,15 @@
  * 8 | EEPROM IO6
  * 9 | EEPROM IO7
  * ----+--------------
- * 10 | 74HC595 SER
- * 11 | 74HC595 RCLK
- * 12 | 74HC595 SCLK
+ * A3 | 74HC595 OE
+ * A4 | 74HC595 SER
+ * 11 | 74HC595 SCLK
+ * 12 | 74HC595 RCLK
+ * 13 | 74HC595 CLR
  * ----+--------------
- * A0 | EEPROM CE
+ * A0 | EEPROM WE
  * A1 | EEPROM OE
- * A2 | EEPROM WE
+ * A2 | EEPROM CE
  * ----+--------------
  * 13 | Activity LED
  * ----+--------------
@@ -42,6 +44,14 @@
  * limitations under the License.
  */
 enum MODE {STANDBY, READ, WRITE};
+typedef enum {
+ OK,
+ E_RESET, // reset command received
+ E_CORRUPT, // inbound packet corrupt
+ E_UNEXPECTED, // unexpected packet received
+ E_UNKNOWN // unknown error
+} error;
+
 const unsigned int MAX_PAYLOAD = 63;
 const unsigned int DELAY_US = 10;
 
@@ -64,6 +74,7 @@ const unsigned int ACT_LED = 10;
 const unsigned int dataPins[] = {2, 3, 4, 5, 6, 7, 8, 9};
 
 MODE mode = NULL;
+error errno = OK;
 
 
 void setup() {
@@ -91,12 +102,13 @@ void setup() {
 
 /*
  * Reads the next message from the serial port and copies its payload into
- * the global `buf` byte array.
+ * the specified `buf` byte array.
  * 
  * This function can participate in explicit flow control by sending an
  * explicit acknowledgement message if `sendAck` is `true`.
  *
- * Returns the number of bytes that were copied into `buf` (0 for acks).
+ * Returns the number of bytes that were copied into `buf` (0 for acks), or -1
+ * if there was an error (check global `errno`).
  */
 int receive(byte *buf, size_t len, bool sendAck) {
  int l;
@@ -106,11 +118,12 @@ int receive(byte *buf, size_t len, bool sendAck) {
 
  if (l > 0) {
  if (Serial.readBytes(buf, min(l, len)) != l) {
- error();
+ errno = E_CORRUPT;
+ return -1;
  }
  }
- if (sendAck) {
- send(NULL, 0, false);
+ if (sendAck && send(NULL, 0, false) == -1) {
+ return -1;
  }
  return l;
 }
@@ -121,18 +134,29 @@ int receive(byte *buf, size_t len, bool sendAck) {
  *
  * This function enforces flow control, blocking until the client has
  * acknowledged receipt with a 0-byte ack.
+ *
+ * Returns 0 on success, or -1 if an error occurred, in which case the global
+ * `errno` variable gets set.
  */
-void send(byte *buf, size_t len, bool waitForAck) {
+int send(byte *buf, size_t len, bool waitForAck) {
  Serial.write(len);
  if (len > 0) {
  Serial.write(buf, len);
  }
  if (waitForAck) {
  byte buf[1 + MAX_PAYLOAD];
- if (receive(buf, MAX_PAYLOAD, false) != 0) {
- error();
+ int len = receive(buf, MAX_PAYLOAD, false);
+ if (len != 0) {
+ if (len == 1 && buf[0] == 'r') {
+ // reset
+ errno = E_RESET;
+ } else if (len != -1) {
+ errno = E_UNEXPECTED;
+ }
+ return -1;
  }
  }
+ return 0;
 }
 
 void pulse(int pin) {
@@ -198,8 +222,11 @@ void writeAddr(unsigned int addr, byte val) {
 /*
  * Writes the full contents of the EEPROM to the serial port in sequential
  * messages of up to 63 bytes, waiting for explicit acknowledgement of each.
+ *
+ * Returns 0 on success, -1 on error, in which case the global `errno` variable
+ * will be set.
  */
-void dump() {
+int dump() {
  byte payload[MAX_PAYLOAD];
  unsigned int i = 0;
 
@@ -208,42 +235,55 @@ void dump() {
 
  if (addr > 0 && i == 0) {
  // payload at capacity, send out:
- send(payload, sizeof(payload), true);
+ if (send(payload, sizeof(payload), true) == -1) {
+ return -1; // abort immediately
+ }
  }
  payload[i++] = readAddr(addr);
  }
 
  if (i) {
  // send remainder
- send(payload, i, true);
+ return send(payload, i, true);
  }
+ return 0;
 }
 
 /*
  * Reads the specified number of bytes from the serial port and writes them
  * to the EEPROM.
  *
  * This requires the Arduino to be in WRITE mode.
+ *
+ * Returns 0 on success, -1 on error, in which case the global `errno` variable
+ * gets set.
  */
-void load(unsigned int len) {
+int load(unsigned int len) {
  unsigned int addr = 0;
  byte buf[1 + MAX_PAYLOAD];
 
  while (addr < len) {
- unsigned int cnt = receive(buf, sizeof(buf), true);
+ int cnt = receive(buf, sizeof(buf), true);
+ if (cnt == -1) {
+ // unexpected error; abort immediately
+ return -1;
+ }
 
- for (unsigned int i = 0; i < cnt; i++) {
+ for (int i = 0; i < cnt; i++) {
  writeAddr(addr++, buf[i]);
  delay(5);
  }
  }
+ return 0;
 }
 
 /*
  * Switches the pin mode for the I/O pins to OUTPUT, pulls EEPROM_CE LOW and
  * EEPROM_OE HIGH.
+ *
+ * Returns 0 on success, or -1 on error.
  */
-void writeMode() {
+int writeMode() {
  digitalWrite(EEPROM_CE, LOW);
  digitalWrite(EEPROM_OE, HIGH);
  digitalWrite(EEPROM_WE, HIGH);
@@ -254,13 +294,16 @@ void writeMode() {
 
  delayMicroseconds(DELAY_US);
  mode = WRITE;
+ return 0;
 }
 
 /**
  * Switches the pin mode for the I/O pins to INPUT, pulls EEPROM_CE LOW,
  * EEPROM_OE LOW and EEPROM_WE HIGH.
+ *
+ * Returns 0 on success, or -1 on error.
  */
-void readMode() {
+int readMode() {
  if (mode != READ) {
  for (unsigned int i = 0; i < 8; i++) {
  pinMode(dataPins[i], INPUT);
@@ -273,9 +316,10 @@ void readMode() {
  delayMicroseconds(DELAY_US);
  mode = READ;
  }
+ return 0;
 }
 
-void standbyMode() {
+int standbyMode() {
  for (unsigned int i = 0; i < 8; i++) {
  pinMode(dataPins[i], INPUT);
  }
@@ -286,43 +330,57 @@ void standbyMode() {
 
  delayMicroseconds(DELAY_US);
  mode = STANDBY;
+ return 0;
 }
 
-void error() {
- for (int i = 0; i < 5; i++) {
- digitalWrite(ACT_LED, LOW);
- delay(100);
- digitalWrite(ACT_LED, HIGH);
- delay(100);
+/**
+ * Flashes out the errno value and resets the errno variable.
+ */
+void processError() {
+ // TODO: different patterns for different errors
+ if (errno != OK) {
+ for (int i = 0; i < 5; i++) {
+ digitalWrite(ACT_LED, HIGH);
+ delay(100);
+ digitalWrite(ACT_LED, LOW);
+ delay(100);
+ }
  }
+ // clear global error state
+ errno = OK;
 }
 
 void loop() {
  if (Serial.available() > 0) {
  byte buf[1 + MAX_PAYLOAD];
  digitalWrite(ACT_LED, HIGH);
 
- unsigned int len = receive(buf, sizeof(buf), false);
+ const int len = receive(buf, sizeof(buf), false);
+ if (len > 0) {
+ if (buf[0] == 0x72 && len == 3) {
+ byte val = readAddr((buf[1] << 8) + buf[2]);
+ send(&val, 1, false);
+
+ } else if (buf[0] == 0x77 && len == 4) {
+ writeAddr((buf[1] << 8) + buf[2], buf[3]);
+ // signal operation completion
+ send(NULL, 0, false);
 
- if (buf[0] == 0x72 && len == 3) {
- byte val = readAddr((buf[1] << 8) + buf[2]);
- send(&val, 1, false);
+ } else if (buf[0] == 0x64 && len == 1) {
+ dump();
 
- } else if (buf[0] == 0x77 && len == 4) {
- writeAddr((buf[1] << 8) + buf[2], buf[3]);
- // signal operation completion
- send(NULL, 0, false);
+ } else if (buf[0] == 0x6c && len == 3) {
+ send(NULL, 0, false); // acknowledge cmd message
+ load((buf[1] << 8) + buf[2]);
 
- } else if (buf[0] == 0x64 && len == 1) {
- dump();
- 
- } else if (buf[0] == 0x6c && len == 3) {
- send(NULL, 0, false); // acknowledge cmd message
- load((buf[1] << 8) + buf[2]);
+ } else if (buf[0] == 0x72 && len == 1) {
+ // ignore reset command
 
- } else {
- error();
+ } else {
+ errno = E_UNKNOWN;
+ }
  }
  digitalWrite(ACT_LED, LOW);
  }
+ processError();
 }