Mc9s12xs128 Ultrasonic Ranging

Let's talk about the pins of the Ultrasonic Ranging module:

 

VCC, echo (receiving end), tring (control end), Out (suspended), Gnd

Sequence diagram:

 

Reference code:

Development Environment: freescalcodewarrior 5.0

/*
* Authour: flyreally
*
* A self-written Ultrasonic Ranging module, which is made using the query method,
* Of course, you can also use the interrupt.
*
*/

# Include # Include <mc9s12xs128. h>/* derivative information */
# Pragma link_info derivative "mc9s12xs128"

/* You can change the timer value to implement timing at different times,
The timer length is timer * 10us */
# Define timer 1
# Define tring porta_pa0 // Control End
# Define echo porta_pa1 // Acceptor

Ulong time = 0;

/* N * 10us latency */
Void delay_us (ulong N)
{
Time = N;
While (time );
}

/* IO port initialization */
Void io_init (void)
{
Ddra = 0x02; // A0 output, A1 Input
}


/* Pit initialization to implement 10us timing */
Void pit_init (void)
{
Pitcflmt_pite = 0; // scheduled interrupt channel 0
Pitce_pce0 = 1; // timer channel 0 Enabled
Pitmtld0 = 160-1; // set the initial value of the 8-bit timer, with a 160-bit Frequency Division
Pitld0 = timer-1; // 16-bit timer Initial Value Setting, Timer * 10us
Pitinte_pinte0 = 1; // timer interrupt channel 0 interrupt enabling
Pitcflmt_pite = 1; // timer channel 0 Enabled
}

Void main (void)
{
Ulong T;
Double DIS;

Io_init (); // Io Initialization
Pit_init (); // pit Initialization
Enableinterrupts; // enable interrupt

/* Wait For 200us to complete ultrasonic module initialization */
Delay_us (20 );

While (1)
{
/* Give the control end a high level that exceeds 10 us, and then set it to low */
Tring = 1;
Delay_us (2 );
Tring = 0;

/* Wait for the receiving end to generate a high level and timing */
While (! Echo );
Time = 0xff;
While (ECHO );
T = 0xff-time; // timing
Dis = 1.7 * t; // calculates the distance.
// The delay is 10 ms. For this reason, we can see the time sequence diagram. Different hardware may vary.
Delay_us (1000 );}
}

/* Scheduled pit interruption */
# Pragma code_seg _ near_seg non_banked
Void interrupt 66 pit0 (void)
{
Pittf_ptf0 = 1; // clear the interrupt flag
-- Time;
}