Help understanding 2's complement conversion

[arunb]

Hi,

I am trying to develop a load cell amplifier that uses the CS5520 load cell amplifier ADC, the datasheet mentions that the ADC outputs conversion words MSB first (with the sign bit being outputed first). The entire word length is 24 bits long, 4 bits are flag settings, and the other 20 bits the data, the first bit is the sign bit. The flag bit is outputted last.

It is also mentioned that the data is outputted in 2's complement.

I am able to read the outputted bytes from the ADC, but I do not know how to convert a 2's complement data to the corresponding decimal format.

Kindly also advise how I can convert the data to voltages, the VREF- and VREF+ voltages are -1.29 and 1.23 respectively.

thanks
arunb

Here are some samples of ADC readings (they contain the flag, data and the sign bit), the sign bit is at the extreme left side

Sample 1: 010000000010110100001000
Sample 2: 010000000010110100001000
Sample 3: 010000001010110100001000
Sample 4: 010000001100110100000001

[Ttelmah]

Write the data into a signed int32 called (say) value.
Then:

[arunb]

Thank you for the reply,

Kindly explain the code you have mentioned in the previous post.

Also is it not necessary to convert the 2's complement data to the 'normal' binary form before converting to voltage levels ???.

Please also mention how I can change the binary data to the equivalent voltage level (read by the ADC), as mentioned before the ADC has VREF+ = 1.28 and VREF- = -1.23 V, the resolution the ADC is 20 Bits

thanks
arunb