debugging code for te ACS712, with ATMEGA328P

[pascalbythree]

Can somebody help me out debugging this piece of source code? To read the mA from the ACS712.

PS: A underhand unit for this is maybe a better help.

Greets, Wouter van Wegen, PascalByThree

Code: Pascal  [Select][+][-]

1. program WVW_ACS712;
2.  
3. uses
4.   consoleio, uart, delay;
5.  
6. const
7.    mVperAmp = 100; // 100; // use 100 for 20A Module and 66 for 30A Module
8.    ACSoffset = 2500;
9.  
10.  
11. var RawValue : DWord;
12.     voltage : DWord;
13.     Amps: Dword;
14.     counter : integer;
15.  
16.  
17. //****************************************************************************************************************
18. procedure ModePortB(Pin: byte; Value: Boolean); begin if Value then begin DDRB := DDRB or (1 shl pin);  end else begin DDRB := DDRB and not (1 shl pin);  end; end;
19. procedure WritePortB(Pin: byte; Value: Boolean); begin if Value then begin PORTB := PORTB or (1 shl pin); end else begin PORTB := PORTB and not (1 shl pin); end; end;
20. procedure ModePortD(Pin: byte; Value: Boolean); begin if Value then begin DDRD := DDRD or (1 shl pin);  end else begin DDRD := DDRD and not (1 shl pin);  end; end;
21. procedure WritePortD(Pin: byte; Value: Boolean); begin if Value then begin PORTD := PORTD or (1 shl pin); end else begin PORTD := PORTD and not (1 shl pin); end; end;
22. function ReadPortD(bit: byte): Boolean;         begin Result := PIND and (1 shl bit) <> 0; end;
23. function ReadPortB(bit: byte): Boolean;         begin Result := PINB and (1 shl bit) <> 0; end;
24. function IntToStr(const i: Integer): string; begin Str(i, Result); end;
25. function StrToInt(const s: string): Integer; var code: Integer; begin Val(s, Result, code); end;
26. //****************************************************************************************************************
27.  
28. procedure ADC_Init;
29. const
30.    Port = 0;
31. begin
32.   ADMUX := (1 shl REFS) or (Port and $0F);
33.   ADCSRA := %111 or (1 shl ADEN);
34. end;
35.  
36. function ADC_Read(Port : byte) : integer;
37. begin
38.    ADMUX := (1 shl REFS) or (Port and $0F); // Specify port
39.    ADCSRA := ADCSRA or ( 1 shl ADSC );       // Start measuring
40.  
41.    while (ADCSRA and (1 shl ADSC)) <> 0 do   // Wait until measured
42.      begin
43.      end;
44.  
45.    Result := ADC; // Read out the measured value
46. end;
47.  
48.  
49. function WriteChar(ACh: char; AUserData: pointer): boolean;
50. begin
51.   WriteChar := true;
52.   uart.uart_transmit(ord(Ach));
53. end;
54.  
55. function ReadChar(var ACh: char; AUserData: pointer): boolean;
56. begin
57.   ReadChar:=true;
58.   ACh := char(uart.uart_receive);
59. end;
60.  
61. procedure initIO;
62. begin
63.   uart_init1(115200, true);
64.   OpenIO(Input, @WriteChar, @ReadChar, fmInput, nil);
65.   OpenIO(Output, @WriteChar, @ReadChar, fmOutput, nil);
66.   OpenIO(ErrOutput, @WriteChar, @ReadChar, fmOutput, nil);
67.   OpenIO(StdOut, @WriteChar, @ReadChar, fmOutput, nil);
68.   OpenIO(StdErr, @WriteChar, @ReadChar, fmOutput, nil);
69. end;
70.  
71. begin
72.   initIO;
73.   ModePortB(0,True);
74.  
75.  
76.    // Initialize ADC
77.    ADC_Init;
78.  
79.    counter := 0;
80.    repeat
81.       counter := counter + 1;
82.       if counter = 100 then counter := 1;
83.  
84. //***************** PART TO DEBUG FORUM ************************
85.      RawValue := ADC_Read(0);
86.      voltage := (RawValue * 5000) div 1024;
87.      Amps := Voltage - ACSoffset;
88.      Amps := Amps div mVperAmp;
89. //*****************************************************************************    
90.  
91.  
92.      WriteLn('***************************');      
93.      WriteLn('counter: '+IntToStr(counter));
94.      WriteLn('RawValue: '+IntToStr(RawValue));    
95.      WriteLn('Amps: '+IntToStr(Amps));    
96.      WriteLn('***************************');      
97.  
98.      WritePortB(0,True); // Status LED ON
99.      delay_ms(25);
100.      WritePortB(0,False);
101.      delay_ms(25); // Status LED OFF
102.    until 1=2;
103.  
104. end.

[Laksen]

What's the problem?

[Khrys]

The only thing that caught my eye at first glance is that  ADC_Read  returns a signed integer even though  ADC  is unsigned, but that shouldn't matter since it's never greater than 1023 anyway... what exactly is the problem you're having?

[ccrause]

Can somebody help me out debugging this piece of source code? To read the mA from the ACS712.

What problem do you observe?  What tests have you done, and what measurements were obtained?

[MarkMLl]

Can somebody help me out debugging this piece of source code? To read the mA from the ACS712.

What problem do you observe?  What tests have you done, and what measurements were obtained?

Have you successfully loaded the code onto the target?

Have you verified- e.g. by a startup message- that the expected code is running?

How does the structure of your code compare to examples written in e.g. C?

Have you read and complied with the device datasheet?

MarkMLl

[ackarwow]

Hi @pascalbythree

If your code compiles without problems but does not work as you expect, you can try to "debug" it "manually" by connecting an LED and flashing it at the right moment. With a bit of luck, you can find the code that does not work as you expect. For example, a procedure that should not be executed but is executed, or does not executed while it should...

[dseligo]

Can somebody help me out debugging this piece of source code? To read the mA from the ACS712.

I tried your code (I used potentiometer instead of ACS712) and it seems to work fine.

Pot little above half:

Code: Text  [Select][+][-]

1. ***************************
2. counter: 23
3. RawValue: 619
4. Amps: 5
5. ***************************
6. ***************************
7. counter: 24
8. RawValue: 617
9. Amps: 5
10. ***************************

Pot full:

Code: Text  [Select][+][-]

1. ***************************
2. counter: 90
3. RawValue: 1023
4. Amps: 24
5. ***************************
6. ***************************
7. counter: 91
8. RawValue: 1023
9. Amps: 24
10. ***************************

Pot minimum:

Code: Text  [Select][+][-]

1. ***************************
2. counter: 12
3. RawValue: 0
4. Amps: 23567
5. ***************************
6. ***************************
7. counter: 13
8. RawValue: 0
9. Amps: 23567
10. ***************************

From 0 to 2500mV you have incorrect Amps values because you subtract 2500 (offset) and you get negative number which doesn't divide properly. Maybe that is your problem?

[dseligo]

If negative amps are problem, then solution is simple: you just change Amps type to Longint instead of DWord:

Code: Pascal  [Select][+][-]

1. Amps: Longint;

And then when pot is at 0 I have:

Code: Text  [Select][+][-]

1. **************************
2. counter: 72
3. RawValue: 0
4. Amps: -25
5. ***************************

And at quarter of turn:

Code: Text  [Select][+][-]

1. ***************************
2. counter: 98
3. RawValue: 252
4. Amps: -12
5. ***************************

[pascalbythree]

Or is this already working ? And only need to convert AMPS variable to mA ?

I just need to read out from 10mA to lets say 500mA

PS: the test with a 10K potmeter is going from RawValue = 0 to  RawValue = 1023

[dseligo]

Or is this already working ? And only need to convert AMPS variable to mA ?

Did you change from Amps: Dword; to Amps: Longint;?

I just need to read out from 10mA to lets say 500mA

I also think that it would be better to use mA instead of A.
In line where you convert mV to A (Amps := Amps div mVperAmp;), you could just multiply it by 10 to get mA: Amps := Amps * 10;.

[Khrys]

If negative amps are problem, then solution is simple: you just change Amps type to Longint instead of DWord:

Code: Pascal  [Select][+][-]

1. Amps: Longint;

And then when pot is at 0 I have:

Code: Text  [Select][+][-]

1. **************************
2. counter: 72
3. RawValue: 0
4. Amps: -25
5. ***************************

This is the correct solution. 4294967271  is  0xFFFFFFE7  in hexadecimal and equal to  -25  if interpreted as a signed 32-bit integer. When  RawValue = 0, your output and that of @dseligo match - it's just wrongly formatted.

[pascalbythree]

Code: Pascal  [Select][+][-]

1.      RawValue := ADC_Read(3);
2.      voltage := (RawValue * 5000) div 1024;
3.      Amps := Voltage - ACSoffset;
4.      Amps := Amps div mVperAmp;
5.      Amps := Amps * 10;

like this ? Just to read out mA in a integer ?

[dseligo]

Code: Pascal  [Select][+][-]

1.      RawValue := ADC_Read(3);
2.      voltage := (RawValue * 5000) div 1024;
3.      Amps := Voltage - ACSoffset;
4.      // Amps := Amps div mVperAmp; // this is commented
5.      Amps := Amps * 10;

like this ? Just to read out mA in a integer ?

Just multiply with 10, don't divide with mVperAmp.

And change declaration of Amps so it will calculate negative values correctly:

Code: Pascal  [Select][+][-]

1. var RawValue : DWord;
2.     voltage : DWord;
3.     Amps: Longint; // <-------------------- change it like this
4.     counter : integer;

[pascalbythree]

Thank you bothers! it got to work. Even though the incoming values are quite unstable.

Will be Back!

someday in another topic. 

[dseligo]

Thank you bothers! it got to work. Even though the incoming values are quite unstable.

What are you measuring?
Maybe current really varies with time. If there are small differences then you could average it in software. Or you could filter input signal by putting correct capacitor to the FILTER pin of the ACS712.
If you are measuring AC currents, maybe you want to rectify output. Look at the Allegro's datasheet, Application 4 example.