MIDI generator
Control some MIDI device with ATtiny26. The code can be convert it for any AVR family microcontroller..
Designed by: Stergiopoulos Vasilis
Link: http://www.serasidis.gr/circuits/MidiGener...diGenerator.htm
This circuit based on ATtiny26 but it could be anyone microcontroller of AVR family. Produce stable one MIDI tone and you can change it by press some keys like to change midi channel 0-15 , velocity 0-127, pitch 0-127. It is start from center tone © at channel 0 with velocity 30. Every tone is equivalence with two midi events "note on" and "note off". A LED is used to show the start and stop of the midi tone. This LED is turn-on every time a command is executed by the key pressing.
Control some MIDI device with ATtiny26. The code can be convert it for any AVR family microcontroller..
Designed by: Stergiopoulos Vasilis
Link: http://www.serasidis.gr/circuits/MidiGener...diGenerator.htm
This circuit based on ATtiny26 but it could be anyone microcontroller of AVR family. Produce stable one MIDI tone and you can change it by press some keys like to change midi channel 0-15 , velocity 0-127, pitch 0-127. It is start from center tone © at channel 0 with velocity 30. Every tone is equivalence with two midi events "note on" and "note off". A LED is used to show the start and stop of the midi tone. This LED is turn-on every time a command is executed by the key pressing.
| CODE |
; midi tester ; program by stergio33 (vster@tee.gr) ; this test circuit sends midi notes constantly, just to study the midi protocol ; there are some buttons connected that let you change the channel, pitch and velocity ; designed for ATtiny26. Program the fuse bits so that it runs at 4MHz internal oscilator .NOLIST .INCLUDE "tn26def.inc" .LIST ; Used registers r16 = scratch, timer = r19(MSB), r18, r17 .def Rout = r20; output register to be shifted for midi .def Poa = r21; state of output port A .def cnt = r22; general counter .def key = r23; 1-127 for midi messages .def veloc = r24; 1-127 velocity of note .def channel = r25; 0-15 midi channel .equ midi = 0 ; midi output .equ led = 1 ; led output pin .equ chanSelect = 0; increase channel button .equ VelocDecr = 1; decrease velocity button .equ VelocIncr = 2; increase velocity button .equ KeyInc = 3; increase key button .equ DeChannel = 4; decrease channel .equ KeyDec = 5; decrease key button ; Code starts here .CSEG .ORG $0000 rjmp arxi ; **************** End of interrupt service routines *********** ; ****************** delay routines ************** delay: ldi r19,8 ldi r18,255; delay routine ldi r17,255 del1: dec r17 brne del1 ser r17 dec r18 brne del1 ser r18 dec r19 brne del1 ret sdel: ldi r16,18; short delay at 4Mhz for internal oscilator sdel1: dec r16 brne sdel1 ret ; Rout = r20 output register to be shifted for midi ; Poa = r21 output buffer for port A ; cnt = r22 general counter ; sends a byte (stored in Rout) serially to midi output, starting from LSB send: ldi cnt,10 com Rout sec send2: brcc send3 cbi portA,midi; midi out rjmp send4 send3: sbi portA,midi nop send4: rcall sdel rcall sdel lsr Rout dec cnt brne send2 ret ; ****************** note on ************************************************ ; key = r23 1-127 for midi messages ; veloc = r24 1-127 velocity of note ; channel = r24 0-15 midi channel ; send note on. 1st byte $9n (n=0-f), 2nd:key (0-$7f), 3rd:velocity (0-$7f) ; midi velocity = 31250 bits/sec, so for the duration of a bit is 1/31250 = 32us noteOn: ldi rout,$90; note-on message starts with 9 rjmp note1 noteOf: ldi rout,$80; note-off message starts with 8 note1: sbi porta,led mov r16,channel andi r16,$0f or rout,r16 rcall send rcall sdel mov rout,key rcall send rcall sdel mov rout,veloc rcall send rcall delay cbi porta,led ret ; ************************************************************************ incKey: inc key ; increase key (pitch) andi key,127 sbi porta,led rcall delay cbi porta,led incKe1: ret ; ************************************************************************ decKey: tst key ; decrease key (pitch) breq decKe1 dec key sbi porta,led rcall delay cbi porta,led decKe1: ret ; ************************************************************************ incVeL: ldi r16,10 ; increase velocity add veloc,r16 andi veloc,127 breq incve1 sbi porta,led rcall delay cbi porta,led incVe1: ret ; ************************************************************************ decVeL: ldi veloc,3 ; decrease velocity sbi porta,led rcall delay cbi porta,led ret ; ************************************************************************ inChan: inc channel ; increase channel circular andi channel,15 sbi porta,led rcall delay cbi porta,led inCha1: ret ; ************************************************************************ deChan: tst channel ; decrease channel breq deCha1 dec channel sbi porta,led rcall delay cbi porta,led deCha1: ret ; **************** End of the subroutines section *************** ; ******************** Main program **************************** arxi: ldi r16,RAMEND ; Initiate Stackpointer. out SP,r16 ldi r16,255 out ddra,r16 ; porta is outputs clr r16 out ddrb,r16 ; portb is inputs out porta,r16 ser r16 out portb,r16 ; pull ups for portb clr Poa start: out PortA,Poa ldi channel,0 ldi key,$3c ; start with middle C ldi veloc,30 next: rcall noteOn rcall delay rcall noteOf rcall delay sbis pinB,VelocDecr; decrease velocity button pressed? rcall decVeL sbis pinB,VelocIncr; increase velocity button pressed? rcall IncVel sbis pinB,chanSelect; increase channel button pressed? rcall inChan sbis pinB,KeyInc ; icrease key button pressed? rcall incKey sbis pinB,KeyDec ; decrease key button pressed? rcall decKey sbis pinB,DeChannel; decrease channel button pressed? rcall deChan rjmp next |