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Re: [ts-7000] Re: Regarding ADC calibration

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Subject: Re: [ts-7000] Re: Regarding ADC calibration
From: Eddie Dawydiuk <>
Date: Wed, 28 Feb 2007 10:11:20 -0700 (MST)
Hello,

> I have few questions ::
> 1) Now without giving any input voltage the output using approximation
> method as shown below. How the program is giving 1.665 count when the
> input value is 0 voltage ?

Are you driving the pins low or are they floating?

> 2) Now when i apply constant voltage of 1.5 volt on pin no 4 of DIO1
> Header. and then i ran the program i find the different outputs values
> on every execution even when the applied voltages are same ?

I'm not sure what board you are using so I'm not sure which channel
corresponds to pin 4 on DIO1...? Do you have a voltmeter connected to
pin 4 to verify it is sitting at 1.5V?

> Here is the outputs Both for 1.5 Volt & same current
> A)
> No calibration values found...
> Channel 0: 2.641V
> Channel 1: 1.670V
> Channel 2: 1.665V
> Channel 3: 1.665V
> Channel 4: 1.665V
> B) No calibration values found...
> Channel 0: 0.319V
> Channel 1: 1.665V
> Channel 2: 1.665V
> Channel 3: 1.665V
> Channel 4: 1.665V

//Eddie

> --- In  Eddie Dawydiuk <> wrote:
>>
>> Hello,
>>
>>> I tried to run the sample code at http://www.pastecode.com/14646 which
>>> is lastly updated as of Apr 29, 2005 and found the following output.
>>>
>>> Calibration Values =
>>> [ 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0 0x0  ]
>>> Board has been calibrated by Technologic Systems...
>>> Channel 0: 2.509V
>>> Channel 1: 2.509V
>>> Channel 2: 2.509V
>>> Channel 3: 2.509V
>>> Channel 4: 2.509V
>>>
>>> Now i have few questions regarding the code ::
>>>
>>> 1) why the output shows 0x0 calibration values as according to
>>> http://tech.groups.yahoo.com/group/ts-7000/message/934
>>>   there should be any data ?
>>
>> I'm not sure what version of the code this is, I'd recommend downloading
>> the code in the files section to ensure we are talking about the same
>> code... Unless otherwise programmed an e2 has 0xff at every location.
>> The code therefore assumes if it reads any value other than 0xff
>> at CALIB_LOC in the e2 that the board has been calibrated and assumes
>> the values read are the calibration values. 0x00 is not a valid
>> calibration value. Please download the code from the files section,
>> if you are still seeing calibration values of 0x00 it is possible you
>> e2 was overwritten and therefore the assumption the code makes is
>> invalid. If this is the case simply comment out the following lines
>>
>>    //check if board has stored calibration values
>>    if(buffer[i] != 0xFF)
>>      virgin = FALSE;
>>
>>> 2) In the code, why 0x10000 is being added in the following statement
>>> or if one can eloborate the meaning please (Line No. 181)
>>>     (((((double)(stored_cal[i][1] + 0x10000)   - stored_cal[i][0]) / 2.5
>>> ) * 3.3 ));
>>
>> The onboard ADC returns a 16 bit signed value corresponding to the
>> voltage. You'll need to first look at the EP9301 datasheet to get
>> documentation on 16 bit signed value and the corresponding voltage.
>>
>> It's on page 33
> http://www.cirrus.com/en/pubs/proDatasheet/EP9301_PP5.pdf
>>
>> But to answer your question the code translates the signed return value
>> to an unsigned value.
>>
>>> 3) Also why the following statement is included? (Line No. 190)
>>>     if(avg < 0x7000) avg = avg + 0x10000;
>>
>> See above.
>>
>>> 4) In the code,  #define CALIB_LOC    2027 is used for location of
>>> calibration values but according to ts-manual-rev2.2.pdf
>>>   on page 28 the location is defined as 0x07EB through 0x07FE that
>>> holds the calibration values, so how the mapping is
>>>   done ? (Line No. 14)
>>
>> Decimal 2027 == Hex 0x7EB.
>>
>> //Eddie
>>
>
>
>
>
>
>
> Yahoo! Groups Links
>
>
>
>
>


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