Page 208 - ARM Based Microcontroller Projects Using MBED

194 8. INTERMEDIATE LEVEL PROJECTS

FIG. 8.55 Block diagram of the project.

8.20.4 The PDL

Fig. 8.56 shows the program PDL.

8.20.5 Program Listing

Fig. 8.57 shows the program listing (program: Voltmeter). At the beginning of the pro-
gram, analog port ADC1/0 is configured as analog input using the statement AnalogIn.
The program executes in an endless loop formed using a while statement. Inside this loop,
the voltage is read using the read() statement which returns a floating point data in the range
0.0–1.0. With a 3.3V ADC reference voltage, 0.0 corresponds to 0V and 1.0 corresponds to
+3.3V. The actual analog voltage in millivolts is found by multiplying the data read by
3300. This value is then converted into real physical voltage and stored as millivolts in var-
iable mV. This value is then displayed on the PC screen. This process is repeated every sec-
ond. Fig. 8.58 shows a typical output from the program.

BEGIN
Clear the screen and home the cursor
Display heading
DO FOREVER
Read the analog input voltage as digital value
Convert the reading into voltage in mV
Display the voltage in mV
Wait one second
ENDDO
END
FIG. 8.56 Program PDL.