PSTWO controller emulation

computer guy

Hi everyone,

I need to get the propeller to emulate a keyboard and a PS2 controller("guitar hero" guitar).
Obviously not at the same time but I want it to be changed via a switch.

What is involved in getting this to happen?


Thank you

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Guitar Hero controller using the prop (WIP) --> HERE

Post Edited (computer guy) : 1/18/2009 8:28:49 AM GMT

Leon

I built a 'keyboard wedge' once with an AVR. It shouldn't be difficult to find some similar hardware and software on the web and adapt it for the Propeller.

Leon

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computer guy

Thank you Leon.

I didn't think that it couldn't be done.
The software side I am assuming is as easy as outputting the key codes. e.g 0x27 for the letter "A".
The hardware should be as simple as some pull up resistors and perhaps some transistors to get the 5v required for the PC.

Is this correct?


Thank you

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Mike Green

Here's a nice reference on the PS/2 interface: www.computer-engineering.org/ps2protocol/

Clemens

http://forums.parallax.com/showthread.php?p=675656
I think this was a thread about a usb keyboard emulation - probably not what you are looking for, but cool anyway.

Leon

The interface is just an open-collector transistor, IIRC.

Leon

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computer guy

Thank you everyone

so for PS/2 keyboard.



Just realised that the host does a lot of pre configuration.
Would someone be interested in writing an obex object for "keyboard" and "PS2 controller" emulation.


Thank you

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Post Edited (computer guy) : 6/30/2008 6:05:49 AM GMT

computer guy

I know this is a big ask but I wouldn't ask if i didn't think the entire community would benefit from it.
Some good information can be found here.
www.curiousinventor.com/guides/ps2#mappings
I am more interested in the Guitar Hero controller emulation.


Thank you

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computer guy

Anyone

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Graham Stabler

Imagine how good you would have become at programming if you wrote those objects.

Graham

stevenmess2004

I don't have a link but didn't deSilva have some basic code for doing this (emulating keyboard) or at least talk about it?

computer guy

Graham I would love to learn by writing these objects.
However as someone who has never fully understood any communication protocol and knows little if any ASM I don't even know where to start.

Steven I will search the forums and see what I can find.

There is already objects for a keyboard and a PS2 Controller all that needs to be done is to reverse the functions.



Thank you

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Post Edited (computer guy) : 7/1/2008 12:27:05 PM GMT

computer guy

Steven I searched the forums several times and can only find talk of a keyboard emulator not an actual object or attempt to do so.

Thank you

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allanlane5

"All that needs to be done is reverse the functions" -- this is easy to say, can be hard to do.

So, basically, you're looking for a PS/2 Keyboard "Replacement" -- instead of the Propeller clocking bits OUT of a keyboard (which we already have code for), some external device will be clocking bits OUT of the Propeller. You'll need some level-shifting in there from the 5-volt Keyboard clock to the 3.3 volt Propeller levels, too.

computer guy

"this is easy to say, can be hard to do."
I wasn't saying it would be easy just that there is a starting point.

I was planning on using 2n2222 (or similar) transistors for the 3.3v to 5v level shifting.


Thank you

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computer guy

One nice thing about making your own guitar hero controller is being able to add an auto play function to play the song for you.
I found an article on the net of a VB.net program that does this. Shouldn't be to hard to convert to spin.

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Post Edited (computer guy) : 7/2/2008 8:10:19 AM GMT

computer guy

Ok I will try and code the keyboard code myself.
However I may need some help from time to time as I have never coded in PASM before.
I will basically be reversing all commands in the keyboard driver so that it writes rather than reads.

Wish me luck.

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computer guy

If I was to call the transmit command from the keyboard with 'data' containing a command. Can I then just call the receive command to get the response from the computer?
Or do I have to do something else in between? Also does the receive command store the received data in the 'data' variable?

The propeller quick reference guide has helped me understand allot of the PASM functions.



Thank you

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computer guy

This is really overwhelming, Trying to reverse an object is really hard when you don't know the programming language.
The prop now has to generate the clock signal rather than detect it and it has to initiate most communication.

If someone could at least get a starting point that I could perhaps work on that would be great.

Its the init code that is hard. Getting the prop to identify its self as a keyboard. Once that is done it is just a matter of sending scan codes.


Thank you

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BradC

Starting point?

PUB Main (KeyboardPin) : Ok | Mask
    Mask := 1 << KeyboardPin

[noparse]:)[/noparse]

But seriously, If for some reason you don't or can't understand how the PS2 interface works, why not grab some code (and there is bucketloads of it around) for another processor (pic, avr, hc11). Read it, understand it, port it to the Propeller.

As Calvins dad would say. "It builds character" [noparse]:)[/noparse]

I don't even own a machine with a PS2 input anymore, it's all USB here.

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StefanL38

hello computerguy,


as i read on the website Mike mentioned

www.computer-engineering.org/ps2protocol/

the communication between PC and keyboard is not symmetrical.

As you have difficulties to find a starting point. I think this caused by the idea just to reverse everything.
But "reversing" is not as easy as multipling with minus one

I think it will be easier to start the whole thing new from the basic up

If the Prop should send scancodes this is the case "Communication: Device-to-Host"

http://www.computer-engineering.org/ps2protocol/ said...


"Communication: Device-to-Host"

The PS/2 mouse and keyboard implement a bidirectional synchronous serial protocol.
The bus is "idle" when both lines are high (open-collector).
This is the only state where the keyboard/mouse is allowed begin transmitting data.
The host has ultimate control over the bus and may inhibit communication at any time by pulling the Clock line low.

The device always generates the clock signal.
If the host wants to send data, it must first inhibit communication from the device by pulling Clock low.
The host then pulls Data low and releases Clock.
This is the "Request-to-Send" state and signals the device to start generating clock pulses.

Summary: Bus States
Data = high, Clock = high: Idle state.
Data = high, Clock = low: Communication Inhibited.
Data = low, Clock = high: Host Request-to-Send

All data is transmitted one byte at a time and each byte is sent in a frame consisting of 11-12 bits. These bits are:

* 1 start bit. This is always 0.
* 8 data bits, least significant bit first.
* 1 parity bit (odd parity).
* 1 stop bit. This is always 1.
* 1 acknowledge bit (host-to-device communication only)

so this could be a starting point:
programming a loop that is generating the clock signal and waiting for
the dataline to become low as the signal Prop can start datatransmission

next step:
calculating the parity bit
adding startbit (always 0) 8 databits, paritybit and stopbit (always 1) to a long and shiftout the eleven bits

then adding the check for: host takes dataline high as a signal comm. inhibited by the host
etc. etc.

another website with infos about the protocol
www.beyondlogic.org/keyboard/keybrd.htm

best regards

Stefan

Matthew Hay

Just a quick thought that popped into my head, why not make a wedge and let a real keyboard do most of the work for you?

You'll have to make sure you passthrough everything that the keyboard is giving you but it should eliminate most of the init stuff. Check the sparkfun tutorial for some of their experience with this (the used avr but most of their information will still be useful to you)

www.sparkfun.com/commerce/present.php?p=Key-Counter

computer guy

"The device always generates the clock signal.
If the host wants to send data, it must first inhibit communication from the device by pulling Clock low. "

If the prop is generating a clock signal on the clk line how can the host pull the line low?


Thank you

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StefanL38

Hello computerguy,

first of all - if you don't want to be tricky by switching the IO-Mode of data and clock all the time between Input and Outputmode
you have to use FOUR PINs if the propeller should act as a keyboard emulator.

You can find out this by carefully reading the website
www.computer-engineering.org/ps2protocol/

Maybe i ask how good is your knowledge about electronics?

Take a look at the circuit



if the microcontroller-PIN "C" is low the transistor is "locked"=very high resistance - no current flowing from +5V through the Pull-Up-resistor down to ground
then on microcontroller-PIN "B" there is high-level because of the pull-up-resistor. The circuit +5V-Pull-Up-Transistor-Ground is "openend"

If the microcontroller-PIN "C" is high the transistor is "switched through" low resistance now a current is flowing from +5V through the Pull-Up-resistor down to ground
then on microcontroller-PIN "B" there is low-level because all the voltage drops down "in" the pull-up-resistor

By switching the PIN "C" the clock signal is generated

The clockline is high as long as PIN "C" is low. If - on the other end the HOST connects the clockline to ground
(and closes the circuit) then there will be PIN "B" low WITHOUT PIN "C" beeing high
and the microcontroller (the keyboard-device) has to check for this combination.

By this tricky way of circuitry the host - IN FACT - CAN pulldown the clockline by closing the circuit by himself.

best regards

Stefan

computer guy

So the low of the host overrides the high of the pullup.

So the code needs to check if "pin C" is low and if it is check if "pin B" is low if they both are low for 100us then the host is pulling the clock line low.


Thank you

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computer guy

computer guy said...

So the low of the host overrides the high of the pullup.

So the code needs to check if "pin C" is low and if it is check if "pin B" is low if they both are low for 100us then the host is pulling the clock line low.


Thank you

Also if I was to use 2n2222 transistors wouldn't a 100ohm resistor be needed between the prop and base pin.

Thank you

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StefanL38

hello Computer Guy,

yes a resistor between Prop-PIN and base of the transistor makes extremly sense.

100 Ohms is a little bit low. each transistorTYPE has its own current-amplifyingfactor
most of them in the range 50-150. If the pull-up-resistor is 10kOhms. You have a current of 5V / 10000 Ohm = 0,5mA
So the collector-emitter-current should be 0,5mA. The base-emitter-current steers the collector-emitter-current
let's assume the currentamp-factor is 100: then the base-emitter-current has to be 0,5mA = 500mikroA / 100 = 5 mikroA
The base-resistor has to have a maximumvalue of 3,3V / 0,5 mikroA = 660kOhm

For switching-purposes it's usual to use a 4,7kOhm resistor.
3,3V / 4700 Ohm = 700 mikroA. The collector-emitter-current provided is 70 mA wich is pretty much and sufficient for
digitical logic devices (usually 0,1-10 mA)

i have to make an additional remark

The schematic in the previous posting has a +5V supply and the PC-keyboardinterface works on 5V too.
The propeller runs on max 3,3V. To avoid damage to the propeller you need 1kOhm current-limiting-resistors in serial to PIN A and PIN B
in schematic above

                                 +5V
                                  |                                 
                                PullUp
                                  |                                 
Proppeller PIN A ---- 1kOhm ------+------> to HOST (PC)

if you are not familiar to the basics of transistorelectronics search for a EASY to understand tutorial
What i found at the english wikipedia is HARD to understand and does not cover the basic things
about base-emitter and collector-emitter current.

My experience searching with google in about 15 Minutes is:
an EASY to understand tutorial could'NT be quickly found

here is a link to a german website with two pictures
showing an analogon with water

leifi.physik.uni-muenchen.de/web_ph10/grundwissen/15trans_eff/trans_eff.htm

small base-current small collector-emitter-current


bigger base-current bigger collector-emitter-current


the different with of the waterchannels represents the amplifying-factor for the current

the small base-channel drives the big collector-emitter-channel


best regards

Stefan

Post Edited (StefanL38) : 7/8/2008 8:08:31 AM GMT

scanlime

If you're still looking for a way to emulate the Guitar Hero controller, I have a generic Playstation controller emulator object that might be useful.

It's at svn.navi.cx/misc/trunk/unicone2/psx-base/, as well as on the object exchange.

Guitar Hero controllers are basically just analog PS2 controllers (not Dual Shock- Guitar Hero will work with a Dual Shock emulator, but GH2 doesn't) with the left d-pad button held down. I've tested this emulator object successfully with Guitar Hero and Guitar Hero 2. You just have to be sure to use CONTROLLER_ANALOG mode instead of CONTROLLER_DUAL_SHOCK.

computer guy

Thank you both.

The PS2 GH emulator is more important than the keyboard.

I didn't think of the 1kohm resistor but now that you mention it I remember the need for it.


Thank you

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computer guy

StefanL38,

I have always compared to a transistor as an electronic tap.
The more current that is applied or the more you turn the valve the more current passes from emitter to collector or the more water is allowed to flow.
That has always worked for me.

I just remember that in a previous project a resistor of some value was needed between prop and base pin to prevent the prop from doing damage to the transistor.


Thank you

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computer guy

Micah Dowty,

I have had a look at your emulator and am not sure how to use it.
Could you please write some short code to configure it to emulate an Analog Controller and then send out that the "Square" button has been pushed.
This should be enough to give me a general idea of how to use it.

Also do you have a copy of the schematic for connecting the prop to the PS2?


Thank you

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Post Edited (computer guy) : 7/8/2008 12:48:03 PM GMT