floating point probem in pic18f452

[yaswanthsai]

Hi all, i want to send floating point value to 8 bit port of pic18f452. i am using HITECH C software for coding. for example a=2,4536, i want to send this value to any of PORT of pic18f452. help me in this.

 

[engr.waqas]

you can't send this value to port.

 

[FvM]

You should clarify, how you intend the 8-Bit port to represent a float value. The HITECH C compiler is supporting all float operations provided by the C standard.

 

[cool.man]

Are you want to see the floating number on seven segment using port or trying something else?

 

[yaswanthsai]

actually i am doing wireless pressure control. for this i am preparing two nodes. in one node i am taking voltage value from pressure tank and i am transmitting the same value to the control node. whr i am implementing PI algorithm to control control valve. for this Kp, KI ,error values are in floating point values. so i want to take PI value which is in floating point and i want to trasmitt to the DAC from the 8 bit port. from DAC i wil take corresponding current value to control control valve.

so help me how to take floating point value to the 8 bit port to send to the DAC0808.

 

[btbass]

The DAC0808 is only an 8-bit DtoA converter, you cant send it floating point values.
One way to do it would be to convert your output from the PI controller to a percentage of full scale. Then output to the dac the same percentage of the dacs full scale.

 

[yaswanthsai]

can u plz give any example c coding how to convert percentage full scale from pi controller.

 

[btbass]

The output from the pressure tank must have a full scale value?
So the percentage from the PI controller is

PerCentOutput = (PI_output / Pressure_full_Scale) * 100;

Full scale for the DAC is 256.

The output to the DAC is (PerCentOutput / 100) * 256;

You could simplify this to

DAC = (PI_output / Pressure_full_Scale) * 256;