How to read the CD32-Pad with Atmega8?

Hiho,

for a little funproject i am looking for a simple way to read the values of the CD32-Pad with an Atmel Atmega8. If possible, in BASCOM....i tried many different ways, but never succeded...

[hit]

since i've no clue, i only can advice you to the minimig core sourcecode, i guess its not bascom, but it might give you an idea:
http://home.hetnet.nl/~weeren001/
http://home.hetnet.nl/~weeren001/dow...04_08_2008.zip

have a look in "fpga core/Userio.v" and "fpga core/Minimig1.v". both deal with joystick. so it might help you somehow.

[musashi5150]

Asman and Wepl posted some CD32 pad reading code here at EAB a while ago. It's in 68K of course but might be of some help?

http://eab.abime.net/showpost.php?p=410337&postcount=38

Perhaps....first i need to learn 68k-Assembler and Verilog...;-)

[OddbOd]

Is this close enough?

Very interesting device, have to try it for my pc :-)
Unfortunately it has nothing in common with the CD32-Pad. I am going to read the above sources and try to figure it out.

[Dimlow]

Originally Posted by CrazyIcecap

Hiho,

for a little funproject i am looking for a simple way to read the values of the CD32-Pad with an Atmel Atmega8. If possible, in BASCOM....i tried many different ways, but never succeded...

What exactly are you trying to do ? Maybe i could help, i program a microchip pic chips all the time but have no experience with atmega controllers. The cd32 controller is just a bunch of switches yes ? if so then its easy. if its the same as an Amiga joystick then there is no problem.

How have you tried and failed ? what have you done to fail ? What circuit are you using ?

[Toni Wilen]

CD32 buttons are read serially, it is not simple switches.

Simple theory of operation: load parallel to serial converter (pulse 3rd firebutton pin 0->1->0), read first button, send "clock" pulse (firebutton pin), read next button (2nd firebutton pin) and so on.. After last button has been read state stays at low (or high, don't remember), some games use this to detect if CD32 pad is installed. (note: some clone pads may not have this logic..)

3rd firebutton = 0 = "normal mode" = red and blue buttons can be read normally.
3rd firebutton = 1 = "cd32 mode" = shift read mode, all buttons readable.

(if I remembered correctly..)

[Dimlow]

Very interesting Toni, i never new that! But still it is possible them to read it using a micro controller. Not too difficult. Got any sources for further info on reading it ? I had a search but did not find anything.

iT Was only a quick search.

Yes, thats right. I tried some code in ASM and later in BASCOM, but had no success. But....i don't have the original "Bone", i have a Honeybee CD32 Pad. Basically it is the same as the original pad - except for CMOS-Shift Register instead of TTL and added Autofire (i switched it off!).
Here are some informations and a schematic for the original pad:
http://gerdkautzmann.de/cd32gamepad/cd32gamepad.html

A short video showing what happens, when i press the Buttons: [ Show youtube player ]

This is my BASCOM-AVR-Code (It is Basic for AVR):
(Sorry for my english; as you can see on some words in the code, i am from germany)

    $regfile = "m8def.dat"
$framesize = 32
$swstack = 10
$hwstack = 40
Dim Speicher As Byte

Config Portb = Output                   'Port B as Output
Config Portd = Input                    'Port D as Input
Config Portd.4 = Output

Led0 Alias Portb.0                      'PB0 bis PB5 as Status-LED
Led1 Alias Portb.1
Led2 Alias Portb.2
Led3 Alias Portb.3
Led4 Alias Portb.4
Led5 Alias Portb.5

Select5 Alias Portb.7                   ' PB6 goes to Pin 5 of the Pad (PLoad)
Poweron Alias Portb.6                   '+5V on Pin 7
Clk Alias Portd.4

Poweron = 1
Select5 = 1
Clk = 1

  Led0 = 1
  Led1 = 1
  Led2 = 1
  Led3 = 1
  Led4 = 1
  Led5 = 1
Do
   Select5 = 0
   Config Portd.4 = Output
   Clk = 1
   Waitms 2
   Speicher.0 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.1 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.2 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.3 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.4 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.5 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.6 = Pind.6
   Clk = 0
   Clk = 1
   Waitms 2
   Speicher.7 = Pind.6
   Gosub Taste
   Waitms 5
   Config Portd.4 = Input
   Portd.4 = 1
   Select5 = 1

Loop
  End

Taste:
                       ' All LEDs off.

  If Speicher.0 = 0 Then                'Button A 
Led0 = 0
  Else
Led0 = 1
 End If
  If Speicher.1 = 0 Then                'Button Start
  Led1 = 0
  Else
  Led1 = 1
 End If
   If Speicher.2 = 0 Then               'Button B
   Led2 = 0
  Else
  Led2 = 1
 End If
   If Speicher.3 = 0 Then               'Button C
   Led3 = 0
  Else
  Led3 = 1
 End If
   If Speicher.4 = 0 Then               'Button Left
   Led4 = 0
  Else
  Led4 = 1
 End If
   If Speicher.5 = 0 Then               'Button Right
   Led5 = 0
  Else
  Led5 = 1
 End If
  Return

[Dimlow]

Watched the vid, but no idea what you are saying there, all i can say is nice flashing lights. As for the code, should there be a small delay after each clk = 0 ? Then maybe it will work, i have not looked into your code in detail, but i would have thought there should be that delay there, other wise there is a very very small logic 0 pulse for the clock. maybe too fast for the 74LS165, maybe it should be about 100us or so.

[Dimlow]

So ???? Does it work ???

No, same picture....:-(
I tried a standalone shift-register with some buttons, works pretty good. Why not this pad?

[yaqube]

@CrazyIcecap

Do you power your pad directly form Portb.6 ??? Try to feed it directly from power rail. Also make sure you have good ground connection between the pad and Atmega (signal integrity or ground bouncing might be a problem).

Tried that already, no difference. I have to power it from the port because i want to use the same circuit with a Sega Genesis-Pad (the device is going to be a portable multi-system-joystick/pad-tester); the power- and select-lines are swapped on that device.
Ground connection is good.