I2c code in verilog

[sunitha_vtpl]

Hi,

I want write I2c code for 24 bit register address and 32 bit data width in verilog ,can any one help  me?

Thanks

Sunitha

[gszakacs]

What are you trying to do with this code?  Do you need master code to connect with an external slave device?  Or do you have an external master and want the FPGA to be the slave device?

I2C is a byte-oriented protocol.  There are different ways to handle wider register address, but it is unusual to have wider data.  Do you have a specification for the external device you will be communicating with?

[sunitha_vtpl]

Thanks for reply,

Yes i am connecting SRIO switch with FPGA.Switch has internal registers with 24 bit register address and 32 bit data.

And FPGA will acts as Master and Switch  will act as slave mode.

So to write those registers i want I2c master code for 24 bit register address and 32 bit data,Can please help me?

Regards

Sunitha

[gszakacs]

It would help to have the data sheet for the SRIO switch you're using.  The I2C bus defines a byte-based transfer mechanism with either 7 or 10 bit slave addressing.  Most IC's use a 7-bit slave address for the device.  Internal addressing ("register address") is handled as a simple write, where the first byte after the device address starts the internal address.  For more than 8-bit internal addressing, you would send more address bytes, followed by data to write.  In order to read, you would only send the internal address bytes, then start a read operation, either by issuing a stop followed by a start or using a "repeated start."  Most I2C slaves respond to either mechanism, but I have seen some, notably chips from Analog Devices, which require the repeated start for reads.

As a starting point I have attached a simple I2C master for accessing registers in slaves using a 7-bit device address, 8-bit internal register address, and 8-bit register data.  You could extend this to 24-bit addressing and 32-bit data by adding additional bytes.  Note that you can't just make the "bytes" 24 or 32 bits.  Each byte is followed by an acknowledge cycle and needs to be transmitted independently.  You'll need to look at the data sheet for your device to determine the correct byte order for data or address larger than 8 bits (i.e. LSB first or MSB first).

[sunitha_vtpl]

HI

Thanks for your reply,

Did u work in this code?

Actually i have written Test bench with

sys_clock=100Mhz 

active low Reset

wr_ctrl=1

But even state is also not changing,It is running only one iteration of timer(330 to 0).did i miss anything in testbench?

Thanks

Sunitha

[gszakacs]

Since you didn't post your test bench it's hard to say what you might have missed.  Here's a simple one with no slave attached that shows what happens when you start up, and then attempts a write.  The status at the end will show 6000 hex indicating that there was no acknowledge pulse from the slave on either the address or data cycles.

[sunitha_vtpl]

Hi,

Thanks for your reply,

If i want change ctrl_data with

7 bit slave address

24 bit register address

32 bit data width 

whare i have to modify in this code?can you please tell me,its urgent require for me

Regards

sunitha

[sunitha_vtpl]

Hi,

Thanks for your reply,

If i want change ctrl_data with

7 bit slave address

24 bit register address

32 bit data width 

whare i have to modify in this code?can you please tell me,its urgent require for me

Regards

sunitha

[arun@12]

Hi,

I want write I2c code in verilog ,can any one help  me?

Thanks,

Arun .

[nadhimer]

i dont know what is happening, I barely understand i2c and vhdl, and i dont know what to do. Your video is the best one I have found untill now, thank you.

[pruthvi@007]

can you please share the specification document.

[gszakacs]

The I2C specification is available here

[pruthvi@007]

can you please share the i2c slave code.

[gszakacs]

I shared the code some time ago in this thread.  It's attached to the post.

[pruthvi@007]

can you please share the testbench in which both slave and master should be attached. I was trying second data transfer format as per below mentioned it is not working.

Possible data transfer formats are:
• Master-transmitter transmits to slave-receiver. The transfer direction is not changed
(see Figure 11). The slave receiver acknowledges each byte.
• Master reads slave immediately after first byte (see Figure 12). At the moment of the
first acknowledge, the master-transmitter becomes a master-receiver and the
slave-receiver becomes a slave-transmitter. This first acknowledge is still generated
by the slave. The master generates subsequent acknowledges. The STOP condition
is generated by the master, which sends a not-acknowledge (A) just before the STOP
condition.
• Combined format (see Figure 13). During a change of direction within a transfer, the
START condition and the slave address are both repeated, but with the R/W bit
reversed. If a master-receiver sends a repeated START condition, it sends a
not-acknowledge (A) just before the repeated START condition

[pruthvi@007]

can anyone explain me why the below lines are used in i2c_master code?

  if (ctrl_reg[31])   // reading requires subaddr write then data read
                if (wr_cyc)
                  shift_reg <= {ctrl_reg[23:17],1'b0,1'b1,ctrl_reg[15:8],1'b1,ctrl_reg[30],7'b0,1'b0};
                else
                  shift_reg <= {ctrl_reg[23:17],1'b1,1'b1,8'hff,1'b1,8'b0,1'b0};

[juliachen]

For some reason, when I run the i2c_master and i2c_master_tb you attached, my waveform stop changing number after status[31:0] hits 80000000 and SDA remains zero after falling at the end of status[31:0] = 0. Are there any other steps that is required to run the waveform you showed?

Also, how do I test "read" with the testbench? 

Thank you!

[reddimounika]

can you please share i2c master and slave verilog codes

[reddimounika]

can you please share i2c master and slave codes

[drjohnsmith]

I'm afraid @reddimounika, its very unlikely that anyone here will do your work for you.
we are here to help people learn the Xilinx tools and FPGAs in general,
we are not paid employees in any way of Xilinx.

Taking a step back,
you say at various times verilog and VHDL.
these are totaly different languages.

you say you want to write 24 bits over i2C,
i2C is a byte transfer bus ,

If you 24 bits of data , you need to three times access's

I2C is also a command data bus, so you are going to have to write the command byte first, then the three data bytes.

All this is basic I2C standard.
I strongly suggest you invest a few days reading and understanding the standard.
https://www.nxp.com/docs/en/user-guide/UM10204.pdf

Next you imply you are less than expert at the coding.
At the very least, you need to search for some off the shelf examples of the IP which you can re use.

Xilinx have a number that are externaly provided,

https://www.xilinx.com/products/intellectual-property/nav-interface-interconnect/nav-i2c.html

Open cores is a good place to start if you want open source.
https://opencores.org/

[reddimounika]

can anyone explain me how prescale values are select  for scl generation.

and also explain me below two lines and  why 10'b11 value taken

modulus <= i_clk_div_factor[10:1] - 10'b11;

count_eq_modby2 <= (count == modulus[8:0]);

[drjohnsmith]

as this is clearly a different question, suggest you open a new topic.

[reddimounika]

Thanks for your reply