Digital joystick - analog interface

pik33

So, I have an Atari type digital joystick

Its pins are: up, down, left, fight, trigger, +5, GND.

Moving the joystick shorts one or two of these pins to the ground.

To not waste P2 pins I reused my robot battery voltage measuring object:

' ADC driver for a robot
' v.0.02 - 20220110
' pik33@o2.pl
' MIT License


var
long aresult
long adcpina
long agnd
long avcc
long bresult
long adcpinb
long bgnd
long bvcc



pub start(apin,bpin) :cog    |iii, m, n

adcpina:=apin
adcpinb:=bpin
cog:=coginit(16,@mixer,@aresult)
waitms(100)
return cog

pub measure() :vx,vy  


return 33000*(aresult-agnd)/(avcc-agnd), 33000*(bresult-bgnd)/(bvcc-bgnd)



DAT
              org
mixer         setq #7
              rdlong aaresult,ptra

              fltl   aapin
              wrpin  adc_config1, aapin 
              wxpin  #%00_1101, aapin
              dirh   aapin

              fltl   abpin
              wrpin  adc_config1, abpin 
              wxpin  #%00_1101, abpin
              dirh   abpin

              mov    x, #%001<<6
              add    x,aapin
              setse1 x

loop          waitse1
              rdpin x,aapin
              rdpin x,abpin
              waitse1
              rdpin x,aapin
              rdpin x,abpin   
              waitse1
              rdpin gnda,aapin
              rdpin gndb,abpin 

              wrpin adc_config2, aapin
              wrpin adc_config2, abpin

              waitse1
              rdpin x,aapin
              rdpin x,abpin

              waitse1
              rdpin x,aapin  
              rdpin x,abpin 
              waitse1
              rdpin vcca,aapin  
              rdpin vccb,abpin

              wrpin adc_config3, aapin
              wrpin adc_config3, abpin

              waitse1
              rdpin x,aapin
              rdpin x,abpin
              waitse1
              rdpin x,aapin 
              rdpin x,abpin 

              waitse1
              rdpin aaresult,aapin  
              rdpin abresult,abpin  

              wrpin adc_config1, aapin 
              wrpin adc_config1, abpin 
              setq #7
              wrlong aaresult,ptra

              jmp     #loop          'loop


adc_config1      long    %0000_0000_000_100000_0000000_00_11000_0 ' 100000 gnd
adc_config2      long    %0000_0000_000_100001_0000000_00_11000_0 ' 100001 3v3
adc_config3      long    %0000_0000_000_100011_0000000_00_11000_0 ' 100011 pin

x                long    0

Then I connected pins via resistors.

• up - 1k
• down - 2k
• left - 4k
• right - 8k

The other ends of these resistors were connected to the P2 pin and also, via 8k resistor, to +3v3 (instead of +5)

I also connected +3v3 via 10k resistor to the trigger - not necessary, the P2 can do a pullup itself, but I want a "clear" thing not dependent on pin settings.

Then I had to write a test program:

#include "retromachine.bi"
dim adc as class using "adccog.spin2"

dim x,y,dir as ulong
dim dirt$ as string

startmachine
startvideo

adc.start(16,17)
v.setmode(0)
v.cls(154,147)


do
x,y=adc.measure()
if x<3090 then dir=5 :dirt$="Up-left"
if x>=3090 andalso x<3350 then dir=9 :dirt$= "Up-right  "
if x>=3350 andalso x<4000 then dir=1:dirt$=  "Up        "
if x>=4000 andalso x<4900 then dir=6:dirt$=  "Down-left "
if x>=4900 andalso x<6000 then dir=10:dirt$= "Down-right"
if x>=6000 andalso x<8000 then dir=2:dirt$=  "Down      "
if x>=8000 andalso x<12000 then dir=4:dirt$= "Left      "
if x>=12000 andalso x<20000 then dir=8:dirt$="Right     "
if x>=20000 then dir=0 : dirt$=              "None      "

if y<16000 then pinhi(56)
if y>=16000 then pinlo(56) 

position 1,10: v.write(v.inttostr2(x,8)): position 20,10: v.write(dirt$): position 40,10: v.write(v.inttostr2(y,8))
loop

to discover that the joystick needs servicing (up contact was bad) but after that, the contraption works. 2 pins used instead of 5

The next retro task: connect an analog PC joystick which I also have.