STM32f4xx ADC values to voltage float values

[xtreme_ruler1]

Posted on October 19, 2013 at 04:49The original post was too long to process during our migration. Please click on the attachment to read the original post.

[Tesla DeLorean]

Posted on October 19, 2013 at 05:17

%f not %d

Should have 3 decimal places, so %5.3f ?float yourVoltage = (float)ADCResult * voltsPerBit;

[xtreme_ruler1]

Posted on October 19, 2013 at 05:26

Thanks for the reply.

Variables window shows: ADCResult    4026     maxAdcBits    4095.0     maxVolts    3.0     voltsPerBit    7.3260075E-4     Made the changes but the semi-hosting still shows output as: PC1 Value is: 4027    PC1 Volts is: : 4027   

[Tesla DeLorean]

Posted on October 19, 2013 at 05:30

Most likely a half-assed printf() implementation on the CooCox side, try converting to millivolts, as an integer

 printf(''PC1 MilliVolts is: %d \n\n'', (int)(yourVoltage * 1000.0f) );

[xtreme_ruler1]

Posted on October 19, 2013 at 05:37

Thank-you, that works:

C1 Value is: 3413    PC1 Volts is: : 3413    PC1 MilliVolts is: 2500 3413/4095 * 3 = 2.5003663 Is there anyway to take that milli value and turn it to decimal?

[Tesla DeLorean]

Posted on October 19, 2013 at 05:47

For positive values

int mv = (int)(yourVoltage * 1000.0f);int x = mv / 1000;int y = mv % 1000;printf(''%d.%03d V\n'',x,y); // assuming printf() implementation supports leading zero properly

[xtreme_ruler1]

Posted on October 19, 2013 at 05:50

Works:

PC1 Value is: 3414    PC1 MilliVolts is: 2501     PC1 Voltage is: 2.501 V thanks a bunch.

[Tesla DeLorean]

Posted on October 19, 2013 at 06:06

Assuming that the printf() library is a light-weight integer only version, you might want to see if there is some option to include one that supports floats. Mind you it might have a significantly larger memory footprint, and have more features that you actually want, need, or might use.