Nuts and Volts - November 2014

 enable_interrupts(INT_EXT_H2L);
}

The first state will be OFF, which is signaled by a zero in the nextState value. The final tasks we will perform within the init function include clearing the fremote flag and enabling the external interrupt. A quick look at the stick schematic reveals that the pushbutton I/O signal is pulled up with a 10K resistor. The H2L in the interrupt enable statement instructs the interrupt engine to fire when the pushbutton logic level transitions from logically high to logically low. The main loop of our prototyping stick remote control application consists of a C language switch mechanism that forms a mini state machine:

■ Screenshot 3. Binary patterns are usually sent between remote control devices. These are simply binary patterns that humans can read.

void main(void)
{
 init();
 while(TRUE)
 {
 switch(nextState)
 {
 case 0:
 if(flags.fremote == 1)
 {
 disable_interrupts(INT_EXT);
 delay_ms(100);
 while(input(PBTN));
 while(!input(PBTN));
 for(aryIndex = 0;aryIndex <
 3;aryIndex++)
 {
 fprintf(RADIO,”%c”,msgOFF
 [aryIndex]);
 }
 fprintf(RADIO,” “);
 output_high(RED_LED);
 delay_ms(500);
 output_low(RED_LED);
 nextState = 1;
 flags.fremote = 0;
 while(!input(PBTN));