ADS1232REF: Change displayed unit to Newton

Hi Nils,

Welcome to the E2E forum!  The ADS1232REF is a demonstration board to be used as a weight scale.  Therefore all the calculations within the ADS1232REF relate specifically to weight applied to a load cell.  When making weight measurements on earth, the weight is relative to earth's gravity.   A  Newton is a unit of force. F = m * a, or F = m * 9.8 m/s² on earth.  So your question is really more based on physics than the operation of the ADS1232REF.  You may find information on the web that can help you understand the conversion.  For example : http://hyperphysics.phy-astr.gsu.edu/hbase/mass.html

The ADS1232 actually produces an output code relative to a voltage.  The output code itself has little meaning without knowing specifics relative to the reference voltage, excitation and the output signal from a load cell.  A load cell will have a sensitivity in mV/V and the full-scale output of the load cell is based on some maximum weight.  The calculation of weight is a downward gravitational acceleration and may not back calculate to Newtons without knowing specifics regarding gravity at the location of measure.  

Best regards,

Bob B

Hi Bob, 

thank you for your quick answer. I am well aware of the connection between Newton and kg and know the gravitational acceleration of my location. 
For my usecase it would be easier if the microprocessor already did the conversion from kg to N and directly displayed the value. Can you tell me how I can reprogram the microcontroller to simply multiply the gravitational acceleration?

Regardig the load cell: I have all the data needed to interpret the voltage signal (I know the sensitivity in mv/V, my reference voltage and the maximum weight of the load cell).
In case it is not possible to reprogram the microcontroller: 
Is there an "easy" solution to capture the voltage data, directly convert it to N and display it on a computer. 
I have seen that the ADS1X3X program can capture the voltage in an ASCII file. However I really would like the data to be directly evaluated. 

Best Regards, 

Nils

Hi Nils,

Firmware code for the ADS1232REF is very old code and uses early versions of freeRTOS and tools that are no longer available to compile correctly (think Windows XP vintage).  Also TI legal no longer allows me to send out the code without the code going through a strict approval process.  In short, even if I could give you the code it would be difficult for you to make use of it.  Longer term we plan on creating a new EVM and code that is more portable and easier to use with Code Composer Studio.  

As to the question regarding connection to the virtual COM port, this is much more doable.  If you have a program that can access the COM port, you can control and collect data transmitted from the ADS1232.  This is exactly how the GUI works for the ADS1232REF in that a Labview program connects to the COM port and collects the data as it is streamed from ADS1232.

Particulars for the serial communication are given in section 5 of the ADS1232REF user's guide.  I would highly recommend you first connect to a terminal program like HyperTerminal or TeraTerm to get an understanding of how the data comes from the COM port as well as the communication structure.  This is important for setting up the device for the desired operation.

Data from the ADC is sent by issuing 'sCRLF' (s is for stream data) and the ADS1232REF will start sending data as a 3 byte representation in hex representing a binary 2's complement value.  The conversion code is followed by CRLF.  For example '7FFFFFCRLF' is positive full-scale and '800000CRLF' is negative full-scale.

As I stated earlier the console just sends raw ADC codes.  You will also need to convert the code to the units desired.  The method used in the firmware uses the calculations given in section 2.1.1 of the user's guide.

Best regards,

Bob B