Interrupt-based read

1 files changed, 163 insertions, 88 deletions

diff --git a/main.c b/main.c
index 4858a5e..6c23e32 100644
--- a/main.c
+++ b/main.c
@@ -17,16 +17,29 @@
 #define LIS302DL_CTRLREG1 0x20
 
 typedef enum {
+	TWM_INVALID = 0,
+	TWM_WRITE,
+	TWM_READ_MULTI,
+} twMode;
+
+typedef enum {
 	TWST_WAIT = 0,
 	TWST_OK = 1,
 	TWST_ERR = 2,
 } twStatus;
 
 typedef struct {
+	twMode mode;
 	uint8_t address;
 	uint8_t subaddress;
 	uint8_t data;
 	uint8_t step;
+	/* read data store */
+	uint8_t *retData;
+	/* number of bytes to be read */
+	uint8_t count;
+	/* current byte */
+	uint8_t i;
 	twStatus status;
 } twReq;
 
@@ -72,6 +85,7 @@ void twInit () {
 	TWBR = 2;
 	TWSR |= 0x3; /* set prescaler to 64 */
 
+	twr.mode = TWM_INVALID;
 	twr.status = TWST_ERR;
 }
 
@@ -83,7 +97,8 @@ static bool twWrite (uint8_t address, uint8_t subaddress, uint8_t data) {
 		return false;
 	}
 
-	twr.address = address | TW_WRITE;
+	twr.mode = TWM_WRITE;
+	twr.address = address;
 	twr.subaddress = subaddress;
 	twr.data = data;
 	twr.step = 0;
@@ -95,6 +110,28 @@ static bool twWrite (uint8_t address, uint8_t subaddress, uint8_t data) {
 	return true;
 }
 
+static bool twReadMulti (uint8_t address, uint8_t subaddress,
+		uint8_t *retData, uint8_t count) {
+	/* do not start if request is pending */
+	if (twr.status == TWST_WAIT) {
+		return false;
+	}
+
+	twr.mode = TWM_READ_MULTI;
+	twr.address = address;
+	twr.subaddress = subaddress;
+	twr.retData = retData;
+	twr.count = count;
+	twr.i = 0;
+	twr.step = 0;
+	twr.status = TWST_WAIT;
+	/* wait for stop finish */
+	while (TW_STATUS != 0xf8);
+	twStartRaw ();
+
+	return true;
+}
+
 void ledInit () {
 	/* set led1,led2 to output */
 	DDRB |= (1 << PB6) | (1 << PB7);
@@ -153,12 +190,13 @@ void cpuInit () {
 	CLKPR = 0b00000011;
 }
 
-ISR(TWI_vect) {
-	printf ("interupt hit with step %i\n", twr.step);
+/*	handle interrupt, write request
+ */
+static void twIntWrite () {
 	switch (twr.step) {
 		case 0:
 			if (TW_STATUS == TW_START) {
-				twWriteRaw (twr.address);
+				twWriteRaw (twr.address | TW_WRITE);
 				twFlushRaw ();
 			} else {
 				twr.status = TWST_ERR;
@@ -191,10 +229,119 @@ ISR(TWI_vect) {
 				twr.status = TWST_ERR;
 			}
 			break;
+
+		default:
+			printf ("nope\n");
+			break;
 	}
 	++twr.step;
 }
 
+static void twIntReadMulti () {
+	switch (twr.step) {
+		case 0:
+			if (TW_STATUS == TW_START) {
+				/* write device address */
+				twWriteRaw (twr.address | TW_WRITE);
+				twFlushRaw ();
+				++twr.step;
+			} else {
+				twr.status = TWST_ERR;
+			}
+			break;
+
+		case 1:
+			if (TW_STATUS == TW_MT_SLA_ACK) {
+				/* write subaddress, enable auto-increment */
+				twWriteRaw ((1 << 7) | twr.subaddress);
+				twFlushRaw ();
+				++twr.step;
+			} else {
+				twr.status = TWST_ERR;
+			}
+			break;
+
+		case 2:
+			if (TW_STATUS == TW_MT_DATA_ACK) {
+				/* send repeated start */
+				twStartRaw ();
+				++twr.step;
+			} else {
+				twr.status = TWST_ERR;
+			}
+			break;
+
+		case 3:
+			if (TW_STATUS == TW_REP_START) {
+				/* now start the actual read request */
+				twWriteRaw (twr.address | TW_READ);
+				twFlushRaw ();
+				++twr.step;
+			} else {
+				twr.status = TWST_ERR;
+			}
+			break;
+
+		case 4:
+			if (TW_STATUS == TW_MR_SLA_ACK) {
+				/* send master ack if next data block is received */
+				twFlushContRaw ();
+				++twr.step;
+			} else {
+				twr.status = TWST_ERR;
+			}
+
+		case 5:
+			if (TW_STATUS == TW_MR_DATA_ACK) {
+				twr.retData[twr.i] = TWDR;
+				++twr.i;
+				if (twr.i < twr.count-1) {
+					/* read another byte, not the last one */
+					twFlushContRaw ();
+					/* step stays the same */
+				} else {
+					/* read last byte, send master nack */
+					twFlushRaw ();
+					++twr.step;
+				}
+			} else {
+				twr.status = TWST_ERR;
+			}
+			break;
+
+		case 6:
+			if (TW_STATUS == TW_MR_DATA_NACK) {
+				/* receive final byte, send stop */
+				twr.retData[twr.i] = TWDR;
+				twStopRaw ();
+				twr.status = TWST_OK;
+			} else {
+				twr.status = TWST_ERR;
+			}
+			break;
+
+		default:
+			printf ("twIntReadMulti: nope\n");
+			break;
+	}
+}
+
+ISR(TWI_vect) {
+	switch (twr.mode) {
+		case TWM_WRITE:
+			twIntWrite ();
+			break;
+
+		case TWM_READ_MULTI:
+			twIntReadMulti ();
+			break;
+
+		default:
+			printf ("nope\n");
+			break;
+	}
+}
+
 int main(void) {
 	cpuInit ();
 	ledInit ();
@@ -206,6 +353,7 @@ int main(void) {
 	
 	printf ("initialization done\n");
 
+	/* global interrupt enable */
 	sei ();
 	/* disable power-down-mode */
 	if (!twWrite (LIS302DL, LIS302DL_CTRLREG1, 0b01000111)) {
@@ -213,93 +361,20 @@ int main(void) {
 	}
 	while (twr.status == TWST_WAIT);
 	printf ("final twi status was %i\n", twr.status);
-	cli ();
 
 	while (1) {
-		signed char val[6];
-			twStartRaw ();
-			twWaitRaw ();
-			unsigned char status = 0x0;
-		
-			/* check status code */
-			if ((status = TW_STATUS) == TW_START) {
-		
-				/* write device address and write bit */
-				TWDR = LIS302DL | TW_WRITE;
-				if (TWCR & (1 << TWWC)) {
-					printf("write collision\n");
-				}
-				twFlushRaw ();
-				twWaitRaw ();
-				if ((status = TW_STATUS) == TW_MT_SLA_ACK) {
-				} else {
-					printf ("fail with code %x\n", status);
-				}
-		
-				/* auto increment + subaddress */
-				TWDR = (1 << 7) | 0x28;
-				if (TWCR & (1 << TWWC)) {
-					printf("write collision\n");
-				}
-				twFlushRaw ();
-				twWaitRaw ();
-				if ((status = TW_STATUS) == TW_MT_DATA_ACK) {
-				} else {
-					printf ("fail with code %x\n", status);
-				}
-		
-				/* repeated start */
-				twStartRaw ();
-				twWaitRaw ();
-				if ((status = TW_STATUS) == TW_REP_START) {
-				} else {
-					printf ("fail with code %x\n", status);
-				}
-			
-				/* write device address and read bit */
-				TWDR = LIS302DL | TW_READ;
-				if (TWCR & (1 << TWWC)) {
-					printf("write collision\n");
-				}
-				twFlushRaw ();
-				twWaitRaw ();
-				if ((status = TW_STATUS) == TW_MR_SLA_ACK) {
-				} else {
-					printf ("fail with code %x\n", status);
-				}
-			
-				for (uint8_t i = 0; i < 6; i++) {
-					/* clear twint and wait for response */
-					if (i < 5) {
-						twFlushContRaw ();
-						twWaitRaw ();
-						if ((status = TW_STATUS) == TW_MR_DATA_ACK) {
-						} else {
-							printf ("fail with code %x in val %i\n", status, i);
-						}
-					} else {
-						twFlushRaw ();
-						twWaitRaw ();
-						if ((status = TW_STATUS) == TW_MR_DATA_NACK) {
-						} else {
-							printf ("fail with code %x in val %i\n", status, i);
-						}
-					}
-					unsigned char ret = TWDR;
-					val[i] = ret;
-				}
-			
-				twStopRaw ();
-	
-				/* there is no way to tell whether stop has been sent or not, just wait */
-				_delay_ms (10);
-			} else {
-				printf ("fail with code %x\n", status);
-				_delay_ms (1000);
-			}
-		//printf ("%i/%i/%i\n", (val[1] << 8) | val[0], (val[3] << 8) | val[2], (val[5] << 8) | val[4]);
-		printf ("%i/%i/%i\n", val[1], val[3], val[5]);
+		uint8_t val[6];
+		if (!twReadMulti (LIS302DL, 0x28, val, 6)) {
+			printf ("cannot start read\n");
+		}
+		while (twr.status == TWST_WAIT);
+		printf ("%i/%i/%i\n", (int8_t) val[1], (int8_t) val[3], (int8_t) val[5]);
+		/* XXX: why do we need the delay here? */
+		_delay_ms (250);
 	}
+	/* global interrupt disable */
+	cli ();
 
 	while (1);
 }
+