I have a RPi 4B connected to two MCP23017 chips via I2C reading 32 input lines. I'm trying to poll the GPIOA and GPIOB registers at about 1 Hz. When I have sequential reading set, it cycles through all the registers correctly but when I try to just access the GPIOA and GPIOB registers, it always returns the last write which in this case is the value from the GPPUB and GPPUB. I am leaving the default of Bank 0 set.
What am I missing when I try to disabled sequential addressing?
What am I missing when I try to disabled sequential addressing?
Code:
#include <stdio.h>#include <fcntl.h>#include <unistd.h>#include <stdlib.h>#include <stdint.h>#include <sys/stat.h>#include <sys/types.h>#include <sys/ioctl.h>#include <linux/i2c-dev.h>#define MCP0_ADDR 0x20#define MCP1_ADDR 0x21#define IODIRA 0x00#define IODIRB 0x01#define IPOLA 0x02#define IPOLB 0x03#define IOCON 0x0A#define GPPUA 0x0C#define GPPUB 0x0D#define GPIOA 0x12#define GPIOB 0x13#define OLATA 0x14#define OLATB 0x15#define INPUT 0xFF#define PULLUP 0xFAstatic const char *device = "/dev/i2c-1";uint8_t buffer[2]; int mcp0, mcp1, mcp2;int mcp_init(void) { // Initialize 1st MCP23017 with 0x20 address: mcp0 = open(device, O_RDWR); ioctl(mcp0, I2C_SLAVE, MCP0_ADDR); // Initialize 2nd MCP23017 with 0x21 address: mcp1 = open(device, O_RDWR); ioctl(mcp1, I2C_SLAVE, MCP1_ADDR); // Chip 0x20 buffer[0] = IOCON; buffer[1] = 0x60; // Bank 0, Seq disabled write(mcp0, buffer, 2); // Chip 0x21 buffer[0] = IOCON; buffer[1] = 0x60; // Bank 0, Seq disabled write(mcp1, buffer, 2); // Chip 0x20 buffer[0] = IODIRA; buffer[1] = INPUT; write(mcp0, buffer, 2); // set IODIRA to all inputs buffer[0] = IODIRB; buffer[1] = INPUT; write(mcp0, buffer, 2); // set IODIRB to all inputs // Chip 0x21 buffer[0] = IODIRA; buffer[1] = INPUT; write(mcp1, buffer, 2); // set IODIRA to all inputs buffer[0] = IODIRB; buffer[1] = INPUT; write(mcp1, buffer, 2); // set IODIRB to all inputs // Chip 0x20 buffer[0] = GPPUA; buffer[1] = PULLUP; write(mcp0, buffer, 2); // set IODIRA to all inputs buffer[0] = GPPUB; buffer[1] = PULLUP; write(mcp0, buffer, 2); // set IODIRB to all inputs // Chip 0x21 buffer[0] = GPPUA; buffer[1] = PULLUP; write(mcp1, buffer, 2); // set IODIRA to all inputs buffer[0] = GPPUB; buffer[1] = PULLUP; write(mcp1, buffer, 2); // set IODIRB to all inputs}int main(void) { // Initialize the chips: mcp_init(); printf("init\n"); sleep(1); while(1) { buffer[0] = GPIOA; buffer[1] = 0x00; printf("MCP0 "); if (read(mcp0, buffer, 2) == 2) { printf("%02X %02X ", buffer[0], buffer[1]); } else { printf("XX XX "); } buffer[0] = GPIOA; buffer[1] = 0x00; printf("MCP1 "); if (read(mcp1, buffer, 2) == 2) { printf("%02X %02X \n", buffer[0], buffer[1]); } else { printf("XX XX \n"); } sleep(1); } return 0 ;}Statistics: Posted by gjm27n — Wed Dec 18, 2024 1:09 am