How to pass floating point variables in a string

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I am trying to print strings on LCD using c language. I want to print the voltage and current of my system on the LCD. how do i include float values when printing in a string. I am using SPI to communicate with the LCD.

What i want to print is,
"28.0 VDC 18.0 A"

Where 28.0 and 18.0 are floating point output variables, Vout_Read and Iout_Read. I can't use a printf statement and %f, while trying to do SPI Transfer. Any suggestion or help is greatly appreciated

What I have tried:

I have tried to print messages as is without having a generic variable. I am repeatedly calling different specific strings each with different voltage and current ratings. But i want to generalize this and improve my code's efficiency.

Posted 29-Jun-18 3:08am

Member 13892404

Updated 29-Jun-18 3:25am

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Peter_in_2780 · Accepted Answer · 2018-06-29T03:26:00

Solution 1

sprintf is your friend. Convert your floats and whatever to build a formatted string that you can output over SPI.

Posted 29-Jun-18 3:26am

Peter_in_2780

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Member 13892404 29-Jun-18 10:22am

Thanks for your time and help peter. I have one follow-up question though. The syntax of SPI transfer message is consisting of two arguments. one is the type of value written to the LCD , i.e either a DATA or a COMMAND. and the second argument is the value itself. which is usually a string.

I want this string to hold the floating point variable as part of it. How does using sprintf accommodate that??

If i was to use sprintf to print voltage i would do something like this,

Char string[40];
sprintf(string, "Voltage is = %f", Vout_Read);
puts(str);

But i am using one SPI transfer function to write anything to the LCD.
it's prototype is
void Spi_Transfer_to_LCD ( uint16 Value_type, uint16 Value)

The 16 bit value is typically passed as a string. Now i need that string to print with the generic Vout_Read and Iout_Read variable in it.