Hello Naveen,

Thanks for the response. In the I2C command explanation, I found the below warning. So could you please give the i2cset command format for USER_LED1? :

WARNING

i2cset can be extremely dangerous if used improperly. It can confuse your I2C bus, cause data loss, or have more serious side effects. Writing to a serial EEPROM on a memory DIMM (chip addresses between 0x50 and 0x57) may DESTROY your memory, leaving your system unbootable! Be extremely careful using this program.

Thank you.

Please check the help and manuals for i2cset

e.g. i2cset --help or i2cset -h should give you that.

Typically it is like following:

i2cset -f -y <bus num> <chip address> <reg address> <value>

You need to figure out the address and values for the chip you are writing to.

Refer to TRM, find out the datasheet of the GPIO expander for details of the registers.

Regards,

Nikhil D

Hi Nikhil,

I tried the following command to switch ON the LED1 at P26:

i2cset -y 0 0x21 0x06 0xBF 

But I got "Write Failed" as the response.

Then I tried to change the configuration of P26 to Output with the following command:

i2cset -y 0 0x21 0x0E 0xBF 

Then also i got  "Write Failed" as the response.

I am trying to read the i2c register value with the following command:

i2cget -y 0x21 0x06

I am getting "read failed" as response.

So i2c is not working. What could be the reason and how can I debug this?

You forgot the -f argument

Regards,

Nikhil D

Even with the -f argument, I am getting same result.

What could be the reason and how can I debug this?

if i execute "i2cdetect -l" the i2c0 is listed.

Even with the -f argument, I am getting same result.

What could be the reason and how can I debug this?

if i execute "i2cdetect -l" the i2c0 is listed. Below is the output, where the 0x21 is not listed :

i2cdetect -y 0
Warning: Can't use SMBus Quick Write command, will skip some addresses
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                                                
10:                                                
20:                                                
30: -- -- -- -- -- -- -- --                        
40:                                                
50: 50 51 -- -- -- -- -- -- -- -- -- -- -- -- -- --
60:                                                
70: 

Try i2cdetect -r -y 0

Ideally, i2cdetect should first show the device responding with adrress acks.

Your device needs to be shown first. That confirms the address is correct.

Regards,

Nikhil D

Even with this it is giving the same result.

i2cget, i2cset are failed.

Is it possible to have a call for further clarification? This may speedup the solution. Request your opinion.

Thanks & Regards,

Gurudath

I tried the recommended commands. I am not getting Read/Write Failed status now. However the LED is not blinking.

So I have 2 questions:

1. As mentioned in the same schematic document, the table shows address of the device as 0x21. Which one is correct?

2. As I mentioned in the other post, 

How can we include the slave address mentioned in the datasheet? 

It is ok for me to write a C function if the commands are not yet prepared for this ASIC. So please guide me further.

Hi Nikhil,

This resolved my issue. To summarize, there were 2 mistakes in the earlier try

1. i2c Device address was 0x21 as mentioned in a table of the schematics.
2.  i2c bus number was used as 0 as the i2c0 is mentioned in schematics. There is no additional information that this is mapped to 3 in the actual i2c bus list.

Request you to note the correction of this information in the next release of schematics.

Thanks you very much for your support.

Hi,

Yes, schematics table will be updated to reflect correct address.
Closing this thread.

Regards,
Vishal