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AD7730 incomming Data

Dear Sir...

Iam working on weigher design for 15 Kg range, i can read from internal register of AD7730,

I configured in bipolar mode, HIREF 1 (5V), Range +_20mV 24bit.

The result of calibration Internal Full scale calibration = 0x593CEA

                                       Internal Zero Scale Cal          = 0x800000

I have two problems as follows :

1. if i configure the chip for uni-polar mode the output becomes zeros !!!!!!

2. If i configured for bipolar mode it give me the following result :-

--4/5/2016 19:42:41 [RX] - 59 3C EA 80 00 00  ( Internal Full and Zero Calibration)

--4/5/2016 19:42:41 [RX] - EB B9 A7 E5 FF FF FF FF FF FF FF FE FF F8 5F FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF FF ------ 11  (24 bit bytes)

91 80 80 01 01 23 02 46 02 8C 04 04 08 09 18 12 30 10 60 20 24 40 48 C0          8  (24 bit bytes)

91 80 80 01 01 23 02 46 02 8C 04 04 08 09 18 12 30 10 60 20 24 40 48 C0

91 80 80 01 01 23 02 46 02 8C 04 04 08 09 18 12 30 10 60 20 24 40 48 C0

91 80 80 01 01 23 02 46 02 8C 04 04 08 09 18 12 30 10 60 20 24 40 48 C0

91 80 80 01 01 23 02 46 02 8C 04 04 08 09 18 12 30 10 60 20 24 40 48 C0

91 80 80 01 01 23 02 46 02 8C 04 04 08 09 18 12 30 10 60 20 24 40 48 C0

As you see in first line the result of full and zero calibration as in the data sheet now the coming data from AD7730 is strange but after the first 11 bytes  there are 8 bytes repeated the same even if i disconnect the Load cell.

Any Advice....

Ahmed

Parents
  • Hi Jellenie...

    it's 2 volts and 520millivolts, yes.

    But i have some questions:

    1. Data register is three bytes long, if i configure the chip for 16 bits which bytes should i read first two bytes or last two bytes ?

    2. Why zero calibration for uni and bi-polar is 0x800000 ? it should be 0x000000 for uni-polar as the calibration short the internal analog channel and this is mentioned in page 24 in AD7730/AD7730L data sheet under Bipolar/Unipolar Inputs?

    3. if the the difference analog value is at AIN1(+) and AIN(-) 1 millivolt why in uni-polar the incoming data is 0000000 ?

    4. First i was doubt that i can read or write SPI correct, so to be sure that communication with the chip is ok i programmed DEN bit for channel two as a digital output, it works well. Also i disconnect the master clock from appear on MCLK OUT and worked well, finally after reset AD7730 i read all the default value for registers !!!!!

    Thanks a lot for your quick response.

    Ahmed

Reply
  • Hi Jellenie...

    it's 2 volts and 520millivolts, yes.

    But i have some questions:

    1. Data register is three bytes long, if i configure the chip for 16 bits which bytes should i read first two bytes or last two bytes ?

    2. Why zero calibration for uni and bi-polar is 0x800000 ? it should be 0x000000 for uni-polar as the calibration short the internal analog channel and this is mentioned in page 24 in AD7730/AD7730L data sheet under Bipolar/Unipolar Inputs?

    3. if the the difference analog value is at AIN1(+) and AIN(-) 1 millivolt why in uni-polar the incoming data is 0000000 ?

    4. First i was doubt that i can read or write SPI correct, so to be sure that communication with the chip is ok i programmed DEN bit for channel two as a digital output, it works well. Also i disconnect the master clock from appear on MCLK OUT and worked well, finally after reset AD7730 i read all the default value for registers !!!!!

    Thanks a lot for your quick response.

    Ahmed

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