[SOLVED] this code for interfacing ADC 122S101 is not working

adhul · May 15, 2018

Code Verilog - [expand]
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module adc_12b(clk,d_in,d_out,sclk,cs);
 
 input clk;     //,reset;
 input d_in;
 output [11:0] d_out;
 output sclk,cs;
 
 reg cs;
 reg [11:0] temp;
 reg [1:0] state=2'b00, nxt_state;
 reg [4:0] count,count1;
 reg [11:0] dout;
 
 assign sclk=clk;
 parameter idle=2'b00, read=2'b01;
 
 
 
// always@(posedge clk)
//   begin
//       if(reset)
//       state=idle;
//       else
//       state=nxt_state;
//   end
 always@(posedge clk)
     begin
//       if(reset)
//       count<=0;
//       else 
         if(count>=5'd16)
         count<=0;
         else if(state==idle)
         begin
         count<=0;
         count<=count+1;
         end
         else
         count<=0;
     end
 
 always@(posedge clk)
     begin
//       if(reset)
//       count1<=0;
//       else 
         if(count1>=5'd16)
         count1<=0;
         else if(state==read)
         count1<=count1+1;
         else
         count1<=0;
     end
 
 always @(negedge clk)
     begin
         case(state)
         idle:begin
         if (count==5'd16)
             begin
             nxt_state <= read;
             cs <= 1'd0;
             end
         else
             begin
             nxt_state <= idle;
             cs <= 1'd1;
             end
         end
 
        read:begin
       if(count1<=5'd16)
            begin
            temp[0] <= d_in;
             temp[1] <= temp[0];
             temp[2] <= temp[1];
             temp[3] <= temp[2];
             temp[4] <= temp[3];
             temp[5] <= temp[4];
             temp[6] <= temp[5];
             temp[7] <= temp[6];
             temp[8] <= temp[7];
             temp[9] <= temp[8];
             temp[10] <= temp[9];
             temp[11] <= temp[10];
             nxt_state <= read;
             end
        else
             begin
             nxt_state <= idle;
             dout<=temp; 
             end
        end
    endcase
 end
 assign d_out=dout;
 endmodule

the timing diagram is as below

FvM · May 15, 2018

Why not write a test bench and simulate the module?

You are reading din at a reduced clock rate but operating sclk still at full rate. That can't work. You probably forgot to generate an appropriate sclk.

ads-ee · May 15, 2018

Really you commented out the reset!?
Why?

FvM's suggestion to run a simulation will yield useless results as there will be X's everywhere as the FSM has no information on where to start.

adhul · May 16, 2018

ads-ee said:
Really you commented out the reset!?
Why?

FvM's suggestion to run a simulation will yield useless results as there will be X's everywhere as the FSM has no information on where to start.

Could you please help me in sorting out this issue?

adhul · May 16, 2018

how to increase the clock rate simmilar to that of sclk???

vGoodtimes · May 16, 2018

state is used but never assigned (after initialization).

--edit: The tragedy is that the problem nets would be among the few not shown as X!

sreevenkjan · May 24, 2018

adhul said:

Code Verilog - [expand]
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module adc_12b(clk,d_in,d_out,sclk,cs);
 
 input clk;     //,reset;
 input d_in;
 output [11:0] d_out;
 output sclk,cs;
 
 reg cs;
 reg [11:0] temp;
 reg [1:0] state=2'b00, nxt_state;
 reg [4:0] count,count1;
 reg [11:0] dout;
 
 assign sclk=clk;
 parameter idle=2'b00, read=2'b01;
 
 
 
// always@(posedge clk)
//   begin
//       if(reset)
//       state=idle;
//       else
//       state=nxt_state;
//   end
 always@(posedge clk)
     begin
//       if(reset)
//       count<=0;
//       else 
         if(count>=5'd16)
         count<=0;
         else if(state==idle)
         begin
         count<=0;
         count<=count+1;
         end
         else
         count<=0;
     end
 
 always@(posedge clk)
     begin
//       if(reset)
//       count1<=0;
//       else 
         if(count1>=5'd16)
         count1<=0;
         else if(state==read)
         count1<=count1+1;
         else
         count1<=0;
     end
 
 always @(negedge clk)
     begin
         case(state)
         idle:begin
         if (count==5'd16)
             begin
             nxt_state <= read;
             cs <= 1'd0;
             end
         else
             begin
             nxt_state <= idle;
             cs <= 1'd1;
             end
         end
 
        read:begin
       if(count1<=5'd16)
            begin
            temp[0] <= d_in;
             temp[1] <= temp[0];
             temp[2] <= temp[1];
             temp[3] <= temp[2];
             temp[4] <= temp[3];
             temp[5] <= temp[4];
             temp[6] <= temp[5];
             temp[7] <= temp[6];
             temp[8] <= temp[7];
             temp[9] <= temp[8];
             temp[10] <= temp[9];
             temp[11] <= temp[10];
             nxt_state <= read;
             end
        else
             begin
             nxt_state <= idle;
             dout<=temp; 
             end
        end
    endcase
 end
 assign d_out=dout;
 endmodule

the timing diagram is as below

View attachment 146646

I suggest you do not use nxt_state and assign the state signal to idle or read parameters. If you are planning to then u need to define it properly so that it shifts from state to nxt_state or you can simply write state instead of nxt_state.

1. Instead of using nxt_state use state = idle/read in your code above.
2. You also need to assign if(count1<5'd16) to get your temp value assigned to dout otherwise you do not get any output.

As the other guys mentioned use a test bench to fine tune your code. You just need 2 input signals in your test bench. Are you sure that the din input is just 1 bit?

- - - Updated - - -

ads-ee said:
Really you commented out the reset!?
Why?

FvM's suggestion to run a simulation will yield useless results as there will be X's everywhere as the FSM has no information on where to start.

Reset is commented because for the obvious reason that its not at all used in the module. It should work without reset.

adhul · May 31, 2018

thank you sir.. the code get synthesized.. but when i tried to put it on spartan 6 and the output was observed by varying the potentiometer the last msb bits are not coming and also if the input voltage to the ADC is 3.3V then by 1.7V the 10 leds glows,which means the output is wrong . what the error can be??
i have been doing that but nothing is happening my way..
The code is attached below

Code Verilog - [expand]
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module adc_new1(clk,d_in,,ch,d_out,sclk,cs);
 
 input clk;     
 input d_in;
 output ch;
 output [15:0] d_out;
 output sclk,cs;
 
 wire cs;
 reg [15:0] temp;
 reg [1:0] state=2'b00;
 reg [4:0] count=0;
 reg [4:0]count1=0;
 reg [15:0] dout;
 reg ch=0;
 assign sclk=clk;
 parameter idle=2'b00, read=2'b01;
 assign cs = 1'd0;
 
 
// always@(posedge clk)
//   begin
//       if(reset)
//       state=idle;
//       else
//       state=nxt_state;
//   end
 always@(posedge clk)
     begin
//       if(reset)
//       count<=0;
//       else 
         if(count>5'd3)
         count<=0;
         else if(state==idle)
         begin
         //count<=0;
         count<=count+1;
         end
         else
         count<=0;
     end
 
 always@(posedge clk)
     begin
//       if(reset)
//       count1<=0;
//       else 
         if(count1>5'd15)
         count1<=0;
         else if(state==read)
         count1<=count1+1;
         else
         count1<=0;
     end
 
 always @(posedge clk)
     begin
         case(state)          
         idle:begin
         if (count==5'd15)
             begin
             state <= read;
             //cs <= 1'd0;
             end
         else 
             begin
             state <= idle;
             //cs <= 1'd1;
             end
         end
 
        read:begin
       if(count1<=5'd15)
            begin
            temp[0] <= d_in;
             temp[1] <= temp[0];
             temp[2] <= temp[1];
             temp[3] <= temp[2];
             temp[4] <= temp[3];
             temp[5] <= temp[4];
             temp[6] <= temp[5];
             temp[7] <= temp[6];
             temp[8] <= temp[7];
             temp[9] <= temp[8];
             temp[10] <= temp[9];
             temp[11] <= temp[10];
                 temp[12] <= temp[11];
                 temp[13] <= temp[12];
                 temp[14] <= temp[13];
                 temp[15] <= temp[14];
             state <= read;
             end
        else
             begin
             state <= idle;
             dout<=temp; 
             end
        end
    endcase
 end
 assign d_out=dout;
 endmodule

FvM · May 31, 2018

CS is not operated in the latest code, can't work.

- - - Updated - - -

Additional points, you never mentioned the clock frequency driving your design. Consider that ADC122S101 must keep an SCLK range of 8 to 16 MHz. I see that you have been playing around with clock edges. It's correct to read DOUT at the rising edge of SCLK, to comply with the datasheet specification, CS (and also DIN, if utilized) must be set at the falling SCLK edge.

The best way to achieve it is to clock the design at double SCLK frequency and toggle SCLK in your design.

adhul · May 31, 2018

FvM said:
CS is not operated in the latest code, can't work.

- - - Updated - - -

Additional points, you never mentioned the clock frequency driving your design. Consider that ADC122S101 must keep an SCLK range of 8 to 16 MHz. I see that you have been playing around with clock edges. It's correct to read DOUT at the rising edge of SCLK, to comply with the datasheet specification, CS (and also DIN, if utilized) must be set at the falling SCLK edge.

The best way to achieve it is to clock the design at double SCLK frequency and toggle SCLK in your design.

K

Sir,
Sorry i put the wrong code this was the code

Code:

module adc_new1(clk,d_in,,ch,d_out,sclk,cs);
 
 input clk;     
 input d_in;
 output ch;
 output [11:0] d_out;
 output sclk,cs;
 
 reg cs;
 reg [11:0] temp;
 reg [1:0] state=2'b00;
 reg [4:0] count=0,count1=0;
 reg [11:0] dout;
 reg ch=0;
 assign sclk=clk;
 parameter idle=2'b00, read=2'b01;
 
 
 
// always@(posedge clk)
//   begin
//       if(reset)
//       state=idle;
//       else
//       state=nxt_state;
//   end
 always@(posedge clk)
     begin
//       if(reset)
//       count<=0;
//       else 
         if(count>=5'd16)
         count<=0;
         else if(state==idle)
         begin
         count<=0;
         count<=count+1;
         end
         else
         count<=0;
     end
 
 always@(posedge clk)
     begin
//       if(reset)
//       count1<=0;
//       else 
         if(count1>=5'd16)
         count1<=0;
         else if(state==read)
         count1<=count1+1;
         else
         count1<=0;
     end
 
 always @(negedge clk)
     begin
         case(state)          
         idle:begin
         if (count==5'd16)
             begin
             state <= read;
             cs <= 1'd0;
             end
         else 
             begin
             state <= idle;
             cs <= 1'd1;
             end
         end
 
        read:begin
       if(count1<5'd16)
            begin
            temp[0] <= d_in;
             temp[1] <= temp[0];
             temp[2] <= temp[1];
             temp[3] <= temp[2];
             temp[4] <= temp[3];
             temp[5] <= temp[4];
             temp[6] <= temp[5];
             temp[7] <= temp[6];
             temp[8] <= temp[7];
             temp[9] <= temp[8];
             temp[10] <= temp[9];
             temp[11] <= temp[10];
             state <= read;
             end
        else
             begin
             state <= idle;
             dout<=temp; 
             end
        end
    endcase
 end
 assign d_out=dout;
 endmodule

FvM · May 31, 2018

Now reading d_in at the wrong SCLK edge.

adhul · Jun 1, 2018

"The best way to achieve it is to clock the design at double SCLK frequency and toggle SCLK in your design."

how to code this ???

sreevenkjan · Jun 4, 2018

Can you tell the clk and sclk value? In the pic share above in your first post, is the waveform of your clk and sclk signal the same? There is missing information of your clk in the timing diagram, can you repost the timing diagram with clk signal in it?

adhul · Jun 13, 2018

thanks for you reply.
In the timing diagram also they didnt mentioned about the clock frequency.
i assumed it to be the same and followed the remaining.

i got the output also. initially i put the frequency as 20 MHz but some bits was missing but later i changed to frequency of about 4 MHz. So i got the output.

KlausST · Jun 13, 2018

Hi,

In the timing diagram also they didnt mentioned about the clock frequency.

clk: is only in the FPGA, thus it is not meantioned in the datasheet
sclk: for sure is specified in the datasheet: 8MHz <= F_sclk <= 16MHz.
--> 20MHz is out of specification.

Please read the datsheet.

Klaus

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[SOLVED] this code for interfacing ADC 122S101 is not working

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