From 82cc507e074956c45bd8c49c07e7d5a0af244af7 Mon Sep 17 00:00:00 2001
From: Sanchayan Maity <maitysanchayan@gmail.com>
Date: Mon, 24 Apr 2017 17:46:30 +0530
Subject: [PATCH] Update code for PCF8591 usage

---
 pcf8591/pcf8591.c | 89 +++++++++++++++++++++++++++++++++--------------
 1 file changed, 62 insertions(+), 27 deletions(-)

diff --git a/pcf8591/pcf8591.c b/pcf8591/pcf8591.c
index 26c4f96..a902411 100644
--- a/pcf8591/pcf8591.c
+++ b/pcf8591/pcf8591.c
@@ -11,58 +11,93 @@
 
 #define PCF8591_ADDRESS		0x48
 
-int main( int argc, char **argv )
+int main(int argc, char **argv)
 {
-	uint8_t i;
 	uint32_t fd;
 	uint32_t ret;
-	uint8_t command[2];
-	uint8_t value[4];
-	useconds_t delay = 2000;
+	uint32_t adc_channel = 0;
+	uint32_t dac_output = 0;
+	uint8_t command[2] = {0};
+	uint8_t value[4] = {0};
+	useconds_t delay = 5000;
 
 	char *dev = "/dev/i2c-0";
 
 	printf("PCF8591 ADC and DAC test code\n");
 
 	fd = open(dev, O_RDWR);
-	if(fd < 0) {
+	if (fd < 0) {
 		perror("Opening i2c device node\n");
-		return 1;
+		return -1;
 	}
 
 	ret = ioctl(fd, I2C_SLAVE, PCF8591_ADDRESS);
-	if(ret < 0) {
+	if (ret < 0) {
 		perror("Selecting i2c device\n");
+		close (fd);
+		return -1;
 	}
 
 	while (true) {
-		for(i = 0; i < 4; i++) {
+		printf("\n1. ADC 2. DAC 3. Exit\n");
+		scanf("%d", &adc_channel);
+		switch (adc_channel) {
+		case 1:
+			printf("\nEnter ADC channel number 0-3:\t");
+			scanf("%d", &adc_channel);
+			if ((adc_channel >= 0) && (adc_channel <= 3)) {
+				/*
+				 * Analog output enable | Read Input i
+				 * See Page 6 of NXP PCF8591 data sheet
+				 */
+				command[0] = 0x40 | ((adc_channel) & 0x03);	/* Control Byte */
+				command[1] = dac_output;					/* DAC Data Register */
 
-			/*
-			 * Analog output enable | Read Input i
-			 * See Page 6 of NXP PCF8591 data sheet
-			 */
-			command[0] = 0x40 | ((i + 1) & 0x03);	/* Control Byte */
-			command[1]++;							/* DAC Data Register */
+				ret = write(fd, &command, 2);
+				if (ret != 2) {
+					perror("i2c write failed");
+					continue;
+				}
+
+				usleep(delay);
+
+				ret = read(fd, &value[0], 1);
+				if(ret != 1) {
+					perror("i2c read failed");
+					continue;
+				}
+
+				printf("\nADC Channel %d: value: %d\n", adc_channel, value[0]);
+			} else {
+				printf("Invalid ADC channel number\n");
+			}
+			break;
+		case 2:
+			printf("Enter DAC value:\t");
+			scanf("%d", &dac_output);
+
+			command[0] = 0x40 | ((adc_channel) & 0x03);	/* Control Byte */
+			command[1] = dac_output & 0xff;				/* DAC Data Register */
 
 			ret = write(fd, &command, 2);
-			if (ret != 2)
-				perror("writing i2c device");
-
-			usleep(delay);
-
-			/* the read is always one step behind the selected input */
-			ret = read(fd, &value[i], 1);
-			if(ret != 1)
-				perror("reading i2c device");
+			if (ret != 2) {
+				perror("i2c write failed");
+				continue;
+			}
 
 			usleep(delay);
+			break;
+		case 3:
+			goto exit;
+			break;
+		default:
+			printf("Invalid input\n");
+			break;
 		}
-
-		printf("0x%02x 0x%02x 0x%02x 0x%02x\n", value[0], value[1], value[2], value[3]);
-		sleep(1);
 	}
 
+exit:
 	close(fd);
+
 	return(0);
 }