Post by thread:Driving a ultrasonic transducer from a PIC (fwd)

many people have requested the code. I shouldn't post it without trying it, but here it is. I hope this is the right program. If this one does not give you a clean 40 kHz, then I will dig deep into my tape backups to find the right one. I kind of remember taking out the swl (small wait loop) and replacing it with a few nop's and then a return. Well, play with it and see what you get. Remember to use a 16c84 and a 1 Mhz oscillator. include <p16cxx.inc> lo equ 0 hi equ 1 inuse equ 2 level equ 0ch level2 equ 0dh counter equ 0eh durat equ 0fh tmpout equ 10h org 0x0000 goto init org 0x0010 init bsf status,rp0 movlw B'00000000' movwf TRISB movlw B'00011111' movwf trisa bcf status,rp0 movlw 0x01 movwf portb movwf tmpout begin ;main program call chirp call pause goto begin chirp ;make sound for dur movlw 0x30 movwf durat cycle bsf tmpout,0 ;on and offs movfw tmpout movwf portb call smwait bcf tmpout,0 movfw tmpout movwf portb call smwait decfsz durat return goto cycle smwait ;small wait loop movlw 0xff movwf level swl decfsz level goto swl return pause ;big wait loop movlw 0xff movwf level movlw 0x10 movwf level2 loop decfsz level2,1 goto next return next decfsz level,1 goto next goto loop end

many people have requested the code. It's been a while since I used it. I hope this is the right program. The program is far from compact or efficient, but it works (I think). Remember to use a 16c84 and a 1 Mhz oscillator. include <p16cxx.inc> lo equ 0 hi equ 1 inuse equ 2 level equ 0ch level2 equ 0dh counter equ 0eh durat equ 0fh tmpout equ 10h org 0x0000 goto init org 0x0010 init bsf status,rp0 movlw B'00000000' movwf TRISB movlw B'00011111' movwf trisa bcf status,rp0 movlw 0x01 movwf portb movwf tmpout begin ;main program call chirp call pause goto begin chirp ;make sound for dur movlw 0x30 movwf durat cycle bsf tmpout,0 ;on and offs movfw tmpout movwf portb call smwait bcf tmpout,0 movfw tmpout movwf portb call smwait decfsz durat return goto cycle smwait ;small wait loop movlw 0xff movwf level swl decfsz level goto swl return pause ;big wait loop movlw 0xff movwf level movlw 0x10 movwf level2 loop decfsz level2,1 goto next return next decfsz level,1 goto next goto loop end