Please help with ADS7825 16-bit ADC

[akokyaw]

Hello,
I have read back problem with ADC7825 which is 16-bit ADC, bipolar 10V. After interfacing with this chip, the read back values are as follow:
For -10V to 0 -> the read back value = 0 to 65536
For 0V to +10V -> the read back value = 0 to 65536

The problem is how to identify the polarity of input voltage? According to datasheet, the format of output is Binary Two's Complement. Please help me.

Thank you,
ako

[PCM programmer]

Two's complement means it's a 'signed' number. When you write the
software driver for the ADC chip, you need to make the 'read' function
return a 'signed int16' value. Then, when you use printf to display it,
you need to specify the %LD format. This will display a signed int16
number.


For example, the following code shows how to return a signed int16
value from your 'read' function.

[akokyaw]

Thank for reply, PCM programmer
I have tried signed int16 variable for read back value. The followings are what I got:
For -10V to -5V -> the read back value = 0 to 32768
For -5V to 0V -> the read back value = -32768 to 0
For 0V to +5V -> the read back value = 0 to 32768
For +5V to 0V -> the read back value = -32768 to 0

Do I have to do hardware detection to polarity of input voltage?
Please indicate where I miss something. Any suggestions or comments would be appreciated.

Thanks,
ako

[nina]

hi akokyaw

could you post your code, please.

tks

nina

[KASMO]

HI, I'M also trying with ads7825 , but i'm novice in this devices , you'r using a serial configuration ? ,, and , however the case , can you post your code (i believe you'r using ccs c compiler),please and thanks for your help

[RM]

Can u post ur code