AN1711 datasheet(9/40 Pages) STMICROELECTRONICS

9 / 40 page

9/40

SOFTWARE TECHNIQUES FOR COMPENSATING ST7 ADC ERRORS

A switch connected to a port pin can be used to inform the software to send the data to a host

PC for display via the SCI communications interface. The port pin used for the switch must be

configured as input. The firmware checks if the switch is pressed (0 is read if switch is pressed

and 1 if open), the ADC readings are then sent to the PC using RS232 communication. You

can use the HyperTerminal application to display the results.

Figure 2. Averaging Algorithm

Total conversion time = (number of samples*ADC conversion time)+ computation time.

Computation time = time taken to read the results, add them together and calculate the av-

erage by dividing the total by the number of samples.

There is a tradeoff between the total conversion time and number of samples used for aver-

aging, depending on the analog signal variations and time available for computation.

yes

Initialise ADC, variables, and select analog

START

Start ADC

Read the ADC output registers after End of Conversion

Average = total/16

channel, Total=0

Use the Result

Add read value to Total

Num. of Conv.

= 16?

AN1711 数据表(PDF) 9 Page - STMicroelectronics