floating point precision for TMS470R1B1M

Hello Jian,

You are seeing the limitation of the 32-bit Single Precision Floating point representation. Not all real numbers can be represented with 100% accuracy. The value you are seeing in the debugger is as close to the desired number of 6.00020002 that can be achieved with this level of floating point precision. This falls back to the principles of floating point and how this translates into real numbers.

Here is a link to a good online calculator that will perform the conversion and show the closest representation given 32-bit single precision format.

http://www.binaryconvert.com/result_float.html?decimal=054046048048048050048048048050

Alternatively, you can do the math yourself using the process described in the wikipedia link below to convert to a binary number and then back its decimal equivalent to see the difference.

http://en.wikipedia.org/wiki/Single-precision_floating-point_format

Jian,

You will not be able to get the exact value in floating point format. I would suggest you using a integer or double precision integer as your software version number.

Thanks and regads,

Zhaohong

Hello Jian,

If you are limited to 32 bits, I can't think of any way to do this. However, if you are able to expand the memory allocation for this value, you could use binary encoded decimal.

For example:

static struct
{
    unsigned int integer_val;          /* binary coded decimal value representer integer portion of version */
    unsigned int decimal_val;         /* binary coded decimal value representing decimal portion of version */
} sw_ver;

 Where assignment is made as follows:

sw_ver.integer_val = 0x00000006;

sw_ver.decimal_val = 0x00020002;

Obviously, this methodology would involve more complex manipulation during software execution for comparing/version checking by software, communication, etc.

The other option would be to store the data as an ASCII string, but this wouldn't be as easily read and interpreted during debug but would be easier to send over a com channel to a PC.

Let me know if this helps.