Verilog Code for I2C Protocol

Posted byShashi SumanPosted inUncategorizedTags:, , , ,

[VISIT NEW POST FOR I2C HERE ]

I2C PROTOCOL

Hola Amigos
I2C devices have been around us for a long time. If you have done any Arduino projects with any peripherals such as Bluetooth (HC-05) or Gyroscope (MPU6050) or Barometer etc you might be surprised you have already used I2C devices. Yes
An I2C basically consists of a master microcontroller and a slave device which responds to the requests of the master. A slave cannot operate on its own. It can’t even communicate with other slaves without having any permission from the master.
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(adsbygoogle = window.adsbygoogle || []).push({});       You may have come across multi-master schematic but it becomes much more complex to handle such situation because of data leakage and also it requires more than 1 microcontrollers. So if you are using an I2C you cannot use any other non-I2C device on the same bus as both SDA and SCL lines are in conjunction with the I2C module. If you find this facility somewhere you are being fooled seriously !!!
 I2C works on 2 signals as SCL and SDA
                                           SCL – Serial Clock
                                           SDA- Serial Data
When SDA is having negedge and SCL is positive level triggered then we have start signal and with every SCL clock, a bit is transferred. Combining up to eight bit the slave receives an address. Then come the R/W signal means whether the slave has to read or write from/to address. AT the very moment after R/W bit the last bit known as acknowledgment bit is sent. Then the slave sends bit by bit data and finalizing by the acknowledge bit and the process comes to a STOP.

 Do remember that when SDA changes the SCL lines must remain stable hence SDA doesn’t change at posedge or nedge of SCL and only on the level of SCL i.e. either 1 or 0.
Here is a demonstration

Pic Credit- Google
 You can easily see the working as I have explained in comparison to the diagrams.
 Ok Coming down to the code

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Starting with Master module and with its inputs

clk = Normal clock
sda = serial data
scl = serial clock
data_wr = data that has to be written if rw = 0;
address = address of slave
register = address of register which has to be read
rw = read or write pin
Next, we move to the declaration of internal variables

temp = to copy address incoming
register2 = to copy register value
scl2x = clock with which sda works to change sda while scl is 0
i = internal counter
n = single counter for start and stop conditions
One must note that initially, we have sda and scl = 1 
After 5ns we turn sda to 0 to introduce start bit condition

From Line 28 to 30 :- we use n as a flag to start scl and scl2x to start bit transmitting
At Line 33 :- Temp stores the concatenated value of the address of slave then rw bit and                                                acknowledge bit
At Line 34:- Incoming register address is stored in register2 internal variable because further we will be using shift operators which doesn’t work on wires and always does on reg data type.
At Line 36 :- If n==1 means start condition and if rw=1 means we have to read register thus                        scl will run upto 50 times
                       Similarly, for rw=1 means, we have to write scl will run 64 times.
                       The value 50 and 64 can be obtained by self-coding 

This piece of code is for stop bit condition.

At Line 55 :- Till value of i reaches 9 we will grab bit by bit from temp
                       Here temp is having 6 bit slave address and 2 bits of rw and ack. Thus each bit                          is being read by shifting temp one by one and reading its MSB
                       Same is happening after Line 60 to get the address of the register
At Line 65 :- if rw ==0 we will receive data which has to be written hence the same process is followed too.

Get the full code with the following link
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Click Here to get the code

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Here is the waveform for rw==0 means write a data to register
Better ZOOM it




Master Model

 Slave Model


So Long

Published by Shashi Suman

I am Shashi Suman. I am passionate about robots, 3D Printing, Verilog and automation. My current dream is make my own 3D printed intelligent robot.

59 thoughts on “Verilog Code for I2C Protocol”

  3. As I said visit the new I2C code. I have made a new post. Search it in project above or you can find the link at the top of this post. Also simulation and implementation on FPGA (RTL) is different. Not every simulatio supports RTL because of some syntax like fork join etc. in the comment section of new post you can find *edited* code to view RTL schematic Here is the linkhttp://www.hellocodings.com/2018/02/i2c-verilog-code-and-working.htmlSo Long

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  6. A newbie (Obviously), what I don't understand is how one actually reads data back from the slave device. I want to program a i2C EEPROM and later read the info back. All the variables in your top module are input only. Should the not be a \”data_returned[7..0]. What am I missing? Thanks in advanceJohn Monahan

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