;***************************************************************************************************; ; ; ; Author: Daniel Hearn ; ; Filename: transmitter.asm ; ; Version: 1.1 ; ; Date: 03-28-2007 ; ; PIC type: PIC16F84A ; ; Clock Speed: 4 mHz ; ; ; ;***************************************************************************************************; ; ; ; Brief Description: Interfaces a 3 button Sega Genesis controller with the wireless reciever by ; ; Mark Feldman. The transmission "send_loop" and delay "pause" routines were written by Mark ; ; Feldman. I only wrote the controller sequence "main_loop". ; ; ; ; Copyright: "send_loop" & "pause" Copyright (c) 2007 Mark Feldman. All Rights Reserved. ; ; "main_loop" Copyright (c) 2007 J Daniel Hearn. All Rights Reservered ; ; ; ; ;***************************************************************************************************; list p=16F84A radix hex #include "C:\Program Files\Microchip\MPASM Suite\p16f84a.inc" __config _HS_OSC & _PWRTE_OFF & _WDT_ON & _CP_OFF ;********** Constants ******************************************************************************; NUM_BUTTONS equ 0Ch CONTROLLER_PORT equ PORTB BUTTON_UP equ 0 BUTTON_DOWN equ 1 BUTTON_LEFT_0 equ 2 BUTTON_RIGHT_0 equ 3 BUTTON_B_A equ 4 BUTTON_C_START equ 5 SELECT_PORT equ PORTA SELECT_BIT equ 3 WIRELESS_PORT equ PORTA WIRELESS_BIT equ 1 ;********* Variables *******************************************************************************; TIMER1 equ 0Ch ; misc variables used by the routines TIMER2 equ 0Dh CURBIT equ 0Eh START_BIT equ 0Fh ; this must be on an odd address to assist ASK-friendly encoding BUTTON_BITS equ (START_BIT+1) STOP_BIT equ (BUTTON_BITS+NUM_BUTTONS) org 0000h ;********* Program Initialization ******************************************************************; init bsf STATUS, RP0 ; select bank 1 bcf WIRELESS_PORT, WIRELESS_BIT ; wireless bit is an output bcf SELECT_PORT, SELECT_BIT ; select bit is an output movlw 0FFh ; controller port is an input movwf TRISB bcf STATUS, RP0 ; select bank 0 clrf START_BIT ; set packet start bit to 0 (gets negated during output) clrf STOP_BIT ; set packet stop bit to 1 (doesn't get negated during output) bsf STOP_BIT, WIRELESS_BIT bcf WIRELESS_PORT, WIRELESS_BIT ; default wireless state is 0 ;********* Controller Read Sequence ****************************************************************; ; ; This section reads the inputs in from the sega genesis controller. The select line must be high ; to read buttons B, C, Left, Right. It should be low to read A and C. It does not affect Up and ; Down. If an input is low its corresponding button is being pressed. The button states are put ; into the array according to how they map to a gamecube controller. I.E. A = B, B = A, C = X ; ;***************************************************************************************************; main_loop movlw BUTTON_BITS ; point FSR to the location of the button states array movwf FSR bcf SELECT_PORT, SELECT_BIT ; sets select line low to read A clrf INDF ; clear destination bit (SNES/GC B) btfss CONTROLLER_PORT, BUTTON_B_A ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry nop ; skip this button in in the array because nothing maps to it clrf INDF ; clear destination bit (SNES/GC Y) nop nop nop incf FSR, F ; move the array ptr to the next entry nop ; skip this button in in the array because nothing maps to it clrf INDF ; clear destination bit (SNES Select) nop nop nop incf FSR, F ; move the array ptr to the next entry bcf SELECT_PORT, SELECT_BIT ; sets select line low to read Start clrf INDF ; clear destination bit (SNES/CG Start) btfss CONTROLLER_PORT, BUTTON_C_START ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry nop ; select line does not matter for Up clrf INDF ; clear destination bit (Up) btfss CONTROLLER_PORT, BUTTON_UP ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry nop ; select line does not matter for Down clrf INDF ; clear destination bit (Down) btfss CONTROLLER_PORT, BUTTON_DOWN ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry bsf SELECT_PORT, SELECT_BIT ; set select line high for Left clrf INDF ; clear destination bit (Left) btfss CONTROLLER_PORT, BUTTON_LEFT_0 ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry bsf SELECT_PORT, SELECT_BIT ; set select line high for Right clrf INDF ; clear destination bit (Right) btfss CONTROLLER_PORT, BUTTON_RIGHT_0 ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry bsf SELECT_PORT, SELECT_BIT ; set select line high for B clrf INDF ; clear destination bit (SNES/GC A) btfss CONTROLLER_PORT, BUTTON_B_A ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F ; move the array ptr to the next entry bsf SELECT_PORT, SELECT_BIT ; set select line high for C clrf INDF ; clear destination bit (SNES/GC X) btfss CONTROLLER_PORT, BUTTON_C_START ; read the button state, is it a 0? bsf INDF, WIRELESS_BIT ; if yes then set destination bit nop ; else leave it cleared incf FSR, F nop ; skip this button in in the array because nothing maps to it clrf INDF ; clear destination bit (SNES/GC L) nop nop nop incf FSR, F ; move the array ptr to the next entry nop ; skip this button in in the array because nothing maps to it clrf INDF ; clear destination bit (SNES/GC R) nop nop nop incf FSR, F ; move the array ptr to the next entry ;********* Transmission Routine ********************************************************************;\ transmit_packet movlw START_BIT ; point FSR to the location of the button states movwf FSR movlw NUM_BUTTONS+2 ; 1 start bit + 12 data bits + 1 stop bit movwf CURBIT send_loop movfw WIRELESS_PORT ; grab the port state andlw ~(1 << WIRELESS_BIT) ; clear the send bit iorwf INDF, W ; move the bit from the buffer into W btfsc FSR, 0 ; change polarity of each bit for ASK-friendly encoding xorlw 1 << WIRELESS_BIT movwf PORTA ; send it to the transmitter incf FSR, F ; move to the next position movlw 4Eh ; hard-coded delay to help pad the pulse out to 250 cycles call delay ; keep the line like this for the duration of the pulse nop decfsz CURBIT, F ; any more bits to send? goto send_loop ; yep, so loop back bcf WIRELESS_PORT, WIRELESS_BIT ; pad the 3.5mS between packets with 0s ;********* Delay Routine *****************************************************************************; ; ; the length of the wireless packet is exactly 3.5ms/3500 cycles, so we now need to pad it out with ; enough 0s to make the main loop exactly 7ms/7000 cycles. i would have liked to put the chip to sleep ; for this to save power, but clock interrupts are disabled during sleep. ; ;*****************************************************************************************************; pause movlw 0ffh call delay movlw 0ffh call delay movlw 0ffh call delay movlw 0ffh call delay movlw 06fh call delay nop clrwdt ; let the watchdog timer know I'm still awake goto main_loop ; all done delay movwf TIMER1 ; this routine causes a delay of (4 + W * 3) instructions dloop decfsz TIMER1,f ; (ie. uS), including the call here and the return goto dloop return end