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How to Read a file into verilog test bench and pass it to the verilog code

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gadagkar.rohit

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Hi,

I need to generate a signal from MATLAB and store the data into a file and then use that file as an input to verilog code.

i just need to know how to read a file in verilog. and in what format should the file be to be able to be read in verilog.

can someone please help me with that.
 

$readmemh() is usful for such tasks.
It reads text file that contains hex values into array.
google readmemh to find some examples.
 
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    lty

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thanks for the reply :)
i have used the same function in the test bench to read the data from the file
but i am still not able to send the data properly to the code.
 

If you could attach the Verlog code and the text file with values, I can try and go over it.
 

i am running the verilog code on quartus II. so i may need to attach the complete project.
should i do that?
 

Sorry, I don't have quartus... (I mainly work with Xilinx).
Maybe 2 files are enough, I will try to go over them:
1. The test-bench Verilog file, that contains the $readmemh() function call, the array that the values are read into, and the loop that goes over the values in this array.
2. The text file with the hex values.
 

its not allowing me to attach the .dat file. the dat file is basically a matlab generated file. i ve generated a random signal and saved the values by converting the signal values to binary.
i have attached the testbench though. i guess there is a problem with the test bench code.
thanks.
 

Attachments

  • TestBench.txt
    655 bytes · Views: 476

1. I would recommend moving the two $readmemh() lines into the last initial block, just before the for() loop.

2. The data files should not be binary files, but text files with hex values readable with a simple text editor (like Notepad).
See example here: **broken link removed**

in your case (16 bit values), the file can look like this:
1f
1234
3d4
55a3
0
9be3

I'm not familiar with MATLAB .dat file. If they don't look like this, you may need some script or Excel function to convert MATLAB output to the above text format

3. To debug the file reading thing, I would suggest adding a $display() line inside the for() loop, just after X39 = mem_X; to print the D39 and X39 values.

4. D39 and X39 are 16 bits vectors. You can't index them with i that counts till 2999.

5. I don't fully understand the Adaptive_LMS_Filter instantiation line. The for() loop starts and ends at time 0, and all the 3000 values go through D39 and X39 during time 0, so after reset is released and clocking starts, the filter will only see a single (constant) value in D39 and X39 - the last value from the file.

6. If you meant to present the list of values to the filter, a new value in each clock, I guess you should do something like the attached.
 

Attachments

  • TestBench.2.v.txt
    672 bytes · Views: 366

hi yoramgr,

this time i have to read a 2-D array...

actually I am processing an image this time. the image is of 288 x 384 x 3 array.

i have taken the pixel values into a txt file in hex format from MATLAB. and as you told me last time, the values in file are hex values and the file itself is not in hex format.

now i have to input those values to verilog and process them.

any suggestions ?
 

I don't use Verilog for testbenches, but in VHDL testbenches , it's easy to read Matlab generated files with general file I/O commands. I guess, it should work with Verilog $fread as well. It's particularly useful, when you want to supply a waveform to a signal processing algorithm, one sample per clock cycle. But you should be also able to write the data to a memory object.
 

Hello FvM,

thank you for you reply.
I have not yet used any one of them...but using which of these, readmemh or fread will i be able to read the complete 2D array and store it as a 2D array.
so that i can process the data by indexing the row and column.
 

You can define 3 arrays, each 2D (assuming 8 bit for each element):

reg [7:0] mem_R[0:287][0:383];
reg [7:0] mem_G[0:287][0:383];
reg [7:0] mem_B[0:287][0:383];

prepare 3 files and try to readmemh 3 times. I'm not sure about the file data order (row by row or column by column), but you can try to play around with it, with small array first.
 

man this is getting frustrating...as u had suggested i tried generating 3 different files for R, G and B.

when i open the text file to check the values the file for G is getting generated properly but for R and B the txt files are showing garbage values.

so i am going to try with only one file. i cant waste more time in generating the 3 files. do u have any suggestion for that.
 

Well, you can always gather all the information in one file, first third of the file will hold R values, second third will hold G values, and last third will hold B values.
Total: file will hold 331776 values (288 x 384 x 3).
In Verilog, define 3 arrays of 2D, and 1 array 1D:

reg [7:0] mem_R[0:287][0:383];
reg [7:0] mem_G[0:287][0:383];
reg [7:0] mem_B[0:287][0:383];
reg [7:0] mem_File[0:331775];

then $readmemh() the file into mem_File array, and add a few loops to copy from mem_File into mem_R, mem_G and mem_B.
 

i have made 3 different files for R, G and B files. now i am just trying to read R the file.

i hve attached the text file. please check it.

what might be the error in this code
module Edge_Detection();

reg clk;



integer fd;
integer i;
integer r;
wire [7:0] im_r[110591:0];


initial
begin
fd = $fopen("C:\Users\Rohit\Documents\MATLAB\image_r.txt","r");
end


initial
begin
clk = 1;
for (i = 0; i <= 110592; i = i+1)
begin
r = $fscanf(fd,"%b",im_r);
$display("%b",im_r);
end
end

always
begin
clk = ~clk;
end

initial
begin
$fclose(fd);
$finish;
end

//Edge_Detection ED (clk);


endmodule
 

Attachments

  • image_r.txt
    972 KB · Views: 174
1. To actually store the data in the array, I think you better define im_r as reg, and not as wire.

2. In the fopen line, there is a space in the filename (between "image_r.tx" and the "t").

3. There is a common confusion with "binary" contents of a file. When you open image_r.txt file with a text editor, and can see "00000001" etc, then that's a text file, and when reading it in pure binary reading function (like $fread), it will give you the ascii codes of "0" (0x30) and "1" (0x31), and a Line-Feed code (0x10) after each 8 characters.
For your file format, you better use:
$readmemb("C:\Users\Rohit\Documents\MATLAB\image_r.txt", im_r);
instead of $fopen, $fread and $fclose.

4. To be able to read your debug data in $display, you better change the "%b" to "%h" or "%0h" (that's a 'zero' before the 'h') .

---------- Post added at 15:19 ---------- Previous post was at 15:18 ----------

another minor issue:
for (i = 0; i <= 110592; i = i+1)
should be:
for (i = 0; i < 110592; i = i+1)
 
Thanks a ton yoramgr!!! :razz:
I have used readmemb. I am able to read from a file and write to a file in verilog properly. I have some issues to solve in MATLAB now.
thanks a lot.

I didnt have to use for loop for readmemb. it reads the whole file at a time
for $display i needed to use the loop to show one data at a time.
same for $fdisplay to write in a file, used a loop.
 

one more question yoramgr

can i use display in a test bench?

can i pass a 2 - D array from a test bench to verilog code.

i am trying to send an array of data 8 bit wide and with depth 110592

its like [7:0] im_b_x[110591:0]
 

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