Page 156 - ARM Based Microcontroller Projects Using MBED

142 8. INTERMEDIATE LEVEL PROJECTS

BEGIN
Group PORT C pins as a single variable
Define the segment bit patterns
Create an array to store the four digits values
Configure PC_8,PC_9,PC_10,PC11as outputs
CNT = 3579
DO FOREVER
Extract all four digits and store in an array
Send bit pattern corresponding to MSD to PORT C
Enable Digit3
Wait for 10ms
Disable MSD Digit
Send bit pattern corresponding to second digitto PORT C
Enable Digit2
Wait for 10ms
Disable Digit2
Send bit pattern corresponding to third digit to PORT C
Enable Digit 1
Wait for 10ms
Disable Digit1
Send bit pattern corresponding to LSD to PORT C
Enable Digit0
Wait for 10ms
Disable Digit0
ENDDO
END
FIG. 8.9 Program PDL.

8.3.6 Program Listing

The program listing (program: SevenSegMux4) is shown in Fig. 8.10. At the beginning of
the program, PORT C lower byte bits are grouped together and assigned to variable called
Segments using the PortOut statement. PC_8, PC_9, PC_10, and PC_11 bits are defined as
Enable3, Enable2, Enable1,and Enable0 and are configured as digital outputs. At the begin-
ning of the main program, variable CNT is set to 3579 and all four digits are disabled. The
remainder of the program runs in an endless loop established using a while statement. Inside
this loop, the digit values of the number to be displayed (i.e., CNT) are extracted and stored in
an array called Digits, where Digits[0] corresponds to Digit 0 value, and Digits[3] corre-
sponds to Digit 3 value. The digit values are then sent to PORT C and the corresponding
digits are enabled for 5ms as in the previous project. The above process is repeated forever
until stopped by the user.