Integrating I2C device using REXLANG

soxso2011 · 2015-11-25 20:09:23

How Rexlang block is used for I2C integration, I have made the connections and able to access it via command line sudo i2cdetect -y 1, but unable to integrate the same using Rexlang or any other block. The PCA9555 GPIO expander is used in my case.

jaroslav_sobota · 2015-11-26 01:00:42

Examples for integrating I2C devices are included in our GitHub repository, links in the Downloads section. After downloading, go into the "Integrating_external_devices/I2C" directory. You should be able to modify the examples for your GPIO expander.

soxso2011 · 2015-11-26 15:04:17

Error message while compiling: validation error:109,[rex i/o driver error]in pin pca955_gpio3:value
validation error:307[file open error] in pin pca9555_task.REXLANG:srcname

Please help!

jaroslav_sobota · 2015-11-26 18:11:52

Without your source files (*.mdl and *.c) there is very little I can do. Zip your files and upload it here.

soxso2011 · 2015-11-27 03:22:48

I am trying to interface PCA9555 I2C i/O port expander, this the following code for i/o extender mpc23017, could you please tell me what to edit for PCA9555.I am unable to access any pins.

/************************************************************
*
* REXLANG - Using the MCP23017 I/O expander via I2C
*
*************************************************************/
#define I2CDEV_FNAME 67 // I2C device is defined by the fname parameter of the REXLANG block (e.g. set it to /dev/i2c-1 on the Raspberry Pi minicomputer)
//assigning inputs to variables, these variables are READ-ONLY
long input(3) digital_out; //the signal controlling the outputs is connected to input u3 of the REXLANG block
long output(10) digital_in; //the state of the input pins is published via output y10 of the REXLANG block
//declaration of variables
long i2c_bufTx[3]; //buffer for transmitting data
long i2c_bufRx[3]; //buffer for receiving data
long i2c_bus_handle;
long i2c_chip_address;
long i2c_write_count;
long i2c_read_count;
long i2c_ret_fun;
//the init procedure is executed once when the REXLANG function block initializes
long init(void)
{
i2c_bus_handle = Open(I2CDEV_FNAME); // open I2C bus
i2c_chip_address = 0x20; // 7-bit address of the I2C device
// !!!!!!!!!!!!!
// By default, IOCON.BANK=0, therefore see Table 1-6 in the datasheet for register mapping
//
// Table 1-5, which confusingly appears sooner in the datasheet, displays register addresses
// for IOCON.BANK=1, which are significantly different
// !!!!!!!!!!!!!

//Setting PORTA to output
i2c_bufTx[0] = 0x00; //register no. (IODIRA)
i2c_bufTx[1] = 0x00; //IODIRA data, bitmask, 0=output, 1=input
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
//Setting PORTB to input
i2c_bufTx[0] = 0x01; //register no. (IODIRB)
i2c_bufTx[1] = 0xFF; //IODIRB data, bitmask, 0=output, 1=input
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
//Enabling pull-up resistors on PORTB
i2c_bufTx[0] = 0x0D; //register no. (GPPUB)
i2c_bufTx[1] = 0xFF; //GPPUB data, bitmask, 0=no pull-up, 1=pull-up enabled
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
return 0;
}
//the main procedure is executed once in each sampling period
long main(void)
{
//Controlling outputs
i2c_bufTx[0] = 0x12; //register no. (GPIOA)
i2c_bufTx[1] = digital_out & 0xFF; //masking the data to control the outputs
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);

//Reading inputs
i2c_bufTx[0] = 0x13; //register no. (GPIOB)
i2c_write_count = 1;
i2c_read_count = 1;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
digital_in = i2c_bufRx[0]; //publishing the received data
return 0;
}
//the exit procedure is executed once when the task is correctly terminated
// (system shutdown, downloading new control algorithm, etc.)
long exit(void)
{
if(i2c_bus_handle>=0) Close(i2c_bus_handle); // close I2C bus
return 0;
}

soxso2011 · 2015-11-27 08:26:10

This is the file I edited for interfacing PCA9555. I have changed the register addresses accordingly in the below program but still unable to access pins. In the c code example for MCP23017, It says By default, IOCON.BANK=0. How to edit this parameter because in PCA9555 both banks are of 8 bit addressing. Please help

/************************************************************
*
* REXLANG - Using the MCP23017 I/O expander via I2C
*
*************************************************************/
#define I2CDEV_FNAME 67 // I2C device is defined by the fname parameter of the REXLANG block (e.g. set it to /dev/i2c-1 on the Raspberry Pi minicomputer)
//assigning inputs to variables, these variables are READ-ONLY
long input(3) digital_out; //the signal controlling the outputs is connected to input u3 of the REXLANG block
long output(10) digital_in; //the state of the input pins is published via output y10 of the REXLANG block
//declaration of variables
long i2c_bufTx[3]; //buffer for transmitting data
long i2c_bufRx[3]; //buffer for receiving data
long i2c_bus_handle;
long i2c_chip_address;
long i2c_write_count;
long i2c_read_count;
long i2c_ret_fun;
//the init procedure is executed once when the REXLANG function block initializes
long init(void)
{
i2c_bus_handle = Open(I2CDEV_FNAME); // open I2C bus
i2c_chip_address = 0x20; // 7-bit address of the I2C device
// !!!!!!!!!!!!!
// , therefore see Table 1-6 in the datasheet for register mapping
//
// Table 1-5, which confusingly appears sooner in the datasheet, displays register addresses
// for IOCON.BANK=1, which are significantly different
// !!!!!!!!!!!!!

//Setting PORTA to output
i2c_bufTx[0] = 0x06; //register no. (IODIRA)
i2c_bufTx[1] = 0x00; //IODIRA data, bitmask, 0=output, 1=input
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
//Setting PORTB to input
i2c_bufTx[0] = 0x07; //register no. (IODIRB)
i2c_bufTx[1] = 0xFF; //IODIRB data, bitmask, 0=output, 1=input
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
//Enabling pull-up resistors on PORTB
i2c_bufTx[0] = 0x0D; //register no. (GPPUB)
i2c_bufTx[1] = 0xFF; //GPPUB data, bitmask, 0=no pull-up, 1=pull-up enabled
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
return 0;
}
//the main procedure is executed once in each sampling period
long main(void)
{
//Controlling outputs
i2c_bufTx[0] = 0x06; //register no. (GPIOA)
i2c_bufTx[1] = digital_out & 0xFF; //masking the data to control the outputs
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);

//Reading inputs
i2c_bufTx[0] = 0x07; //register no. (GPIOB)
i2c_write_count = 1;
i2c_read_count = 1;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
digital_in = i2c_bufRx[0]; //publishing the received data
return 0;
}
//the exit procedure is executed once when the task is correctly terminated
// (system shutdown, downloading new control algorithm, etc.)
long exit(void)
{
if(i2c_bus_handle>=0) Close(i2c_bus_handle); // close I2C bus
return 0;
}

deepak · 2015-11-27 17:16:58

I faced the same problem !. Dont bother with the IOCON.BANK attribute in the c program. Your address for configuring Port A & Port B are correct.(0x06 & 0x07) This is the part of the program what you must edit to read Bank 0 of PCA 9555 as Output and Bank 1 as input.

//the main procedure is executed once in each sampling period
long main(void)
{
//Controlling outputs
i2c_bufTx[0] = 0x06; //CHANGE 0x06 TO 0x02 (REFER PCA 9555 DATASHEET)
i2c_bufTx[1] = digital_out & 0xFF; //masking the data to control the outputs
i2c_write_count = 2;
i2c_read_count = 0;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);

//Reading inputs
i2c_bufTx[0] = 0x07; //CHANGE 0x07 TO 0x01 (REFER PCA 9555 DATASHEET)
i2c_write_count = 1;
i2c_read_count = 1;
i2c_ret_fun = I2C(i2c_bus_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
digital_in = i2c_bufRx[0]; //publishing the received data
return 0;
}

This worked for me successfully.

soxso2011 · 2015-11-28 12:38:25

Yeah...It worked...!!!

soxso2011 · 2015-11-28 12:40:50

//Sending data via I2C
i2c_ret_fun = I2C(i2c_port_handle, i2c_chip_address, i2c_bufTx, i2c_write_count, i2c_bufRx, i2c_read_count);
adc_value = (i2c_bufRx[0]<<8) + i2c_bufRx[1];

Is there any syntax error in these lines??

josar · 2015-11-28 20:47:47

I do not see any syntax error. However, the problem is probably the variable i2c_port_handle, which you should change to i2c_bus_handle, as you were instructed in the other topic. Check the definitions of variables at the beginning of your code. You'll probably find this definition of a variable:

long i2c_bus_handle;

So that's why you get an error when compiling and why you have to make this change.

soxso2011 · 2015-11-29 12:52:45

Yep!!

scoobsalamander · 2017-05-03 19:40:55

...an example with port expander MCP23017 (soxso2011, I hope you don't mind I used a part of your script)

8 inputs and 8 outputs

REX_MCP23017.zip

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#1 2015-11-25 20:09:23