AN1711 datasheet(4/40 Pages) STMICROELECTRONICS

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SOFTWARE TECHNIQUES FOR COMPENSATING ST7 ADC ERRORS

1 GENERAL SOFTWARE CONSIDERATIONS

This section gives some basic guidelines for programming the ADC.

General Procedure

■

Check for fADC (max) supported by the device

■

Select the conversion channel (and start conversion)

■

Poll for End of Conversion

■

Read the ADC conversion results

Special Procedures

■

Entering HALT mode

■

Using a timer with the ADC to perform periodic conversions

Other Special Features

Not all ST7 ADCs have the same features, refer to the datasheet of the ST7 product you are

using for specific information. Depending on the device, you may need to apply these tips in

your ADC software:

■

Using 10-bit ADC as 8-bit ADC

■

Handling Control Bits located in same register as Data LSBs

■

Zooming to low voltage signals with embedded amplifier

1.1 CHECKING FOR FADC (MAX) SUPPORTED BY THE DEVICE

Before configuring the ADC and starting any conversions, you need to check the fADC max-

imum supported by the device. This value is documented in the ST7 datasheets, you should

refer to the ADC electrical characteristics section.

For example:- Some devices have a SPEED bit for working at fCPU/2 but the fADC (max) is 2

MHz. For ST7 devices, fCPU can be up to 8 MHz. In this case you cannot utilize the SPEED bit,

because it will boost fADC to 4 MHz, which is greater than the allowed maximum (fADC (max)

=2 MHz).

If fCPU is 4 MHz or lower (in Run or Slow mode), you can use the SPEED bit to run the ADC

at fCPU/2, and still respect the 2MHz. fADC (max).

Some devices support fADC (max) = 4MHz. It is thus necessary to check the electrical charac-

teristics before configuring the ADC.

AN1711 Scheda tecnica(PDF) 4 Page - STMicroelectronics