main.c

void initI2C(void) {
	char filename[20];
	snprintf(filename, 19, "/dev/i2c-%d", I2C_ADAPTER_NUMBER);
	i2cFile = open(filename, O_RDWR);
	if (i2cFile < 0) {
		printf("I2C File < 0, %d", errno);
		/* ERROR HANDLING; you can check errno to see what went wrong */
		exit(1);
	}
	if (ioctl(i2cFile, I2C_TENBIT, 0) < 0) {
		printf("IOCTL I2C_TENBIT Failed, %d", errno);
		/* ERROR HANDLING; you can check errno to see what went wrong */
		exit(1);
	}
	if (ioctl(i2cFile, I2C_PEC, 0) < 0) {
		printf("IOCTL I2C_PEC Failed, %d", errno);
		/* ERROR HANDLING; you can check errno to see what went wrong */
		exit(1);
	}
}


int i2c_write(unsigned char slaveID, const void *buf, unsigned int length) {
	unsigned int padding = length % 4;
	unsigned int paddedLength = length + (padding > 0 ? 4 - padding : 0) + 1;
	if (!setI2CSlaveAddress(i2cFile, slaveID)) {
		return -1;
	}
	return write(i2cFile, buf, paddedLength) == paddedLength;
}


int i2c_read_inputs(ARPResult *arp, void *buf, unsigned char forceImport, unsigned char *changed) {
	int ret;
	I2CModuleCommand *cmd = (I2CModuleCommand *) buf;
	cmd->msg.size = sizeof(I2CModuleCommand);
	cmd->msg.type = MSG_READ;
	ret = i2c_write(arp->i2cid, buf, cmd->msg.size);
	if (ret) {
		unsigned int io_length = arp->inputs + arp->outputs + 1;
		unsigned int length = sizeof(I2CModuleCommand) + io_length;
		ret = read(i2cFile, buf, length);
		if (length == ret) {
			I2CModuleRead *moduleRead = (I2CModuleRead *) buf;
			//printf("Read module: ret=%d, io_length=%d, size=%d, type=%d\n", ret, io_length, moduleRead->base.size, moduleRead->base.type);
			//printMemoryMap(buf, moduleRead->base.size);
			if (moduleRead->changed || forceImport) {
				memcpy((arp->memoryMap) + arp->outputs, buf + sizeof(I2CModuleRead), arp->inputs);
				*changed = 1;
			}
			return 0;
		} else {
			printf("Read size missmatch (res = %d)\n", ret);
			return 1;
		}
	} else {
		printf("(read %d inputs) Command failed write (res = %d)\n", arp->i2cid, ret);
		return 1;
	}
}


int i2c_write_outputs(ARPResult *arp, void *buf) {
	int ret;
	I2CModuleCommand *cmd = (I2CModuleCommand *) buf;
	cmd->msg.size = (unsigned char) (sizeof(I2CModuleCommand) + arp->outputs);
	cmd->msg.type = MSG_WRITE;
	memcpy((unsigned char *) buf + sizeof(I2CModuleCommand), arp->memoryMap, arp->outputs);
	ret = i2c_write(arp->i2cid, buf, cmd->msg.size);
	if (ret) {
		return 0;
	} else {
		printf("(write %d outputs) Command failed write (res = %d)\n", arp->i2cid, ret);
		return 1;
	}
}