Joystick question

[cybertron]

With the advent of digital joysticks, I'm finding it hard to get hold of an analogue joystick for my beeb. Does anyone know where I can get hold of an old analogue joystick such as a Quickshot, or even just joystick potentiometers, so I can do a 'cut and shut' on a digital joystick? I've looked on the web, and most so called 'joystick potentiometer's appear to be expensive industrial units or analogue industrial joysticks costing a small fortune.

 

[wmmullaney]

Got any thrift stores there? Here they throw those things away....

 

[carlsson]

Strange. For a while last year there was a small flood of BBC joysticks on eBay so I thought they'd be rather common, at least if you don't care about the make or model. Sometimes you may see a joystick interface too; one that converts from 9-pin Atari-style digital to 15-pin BBC analogue. I don't know how well those work, it probably depends on the game what kind of controller it expects. I suppose an interface to fake a digital signal as a "full throttle" analogue signal wouldn't be too hard, but I reckon you'd like to be able to use the modified joystick fully in analogue mode.

 

[cybertron]

Strange. For a while last year there was a small flood of BBC joysticks on eBay so I thought they'd be rather common, at least if you don't care about the make or model. Sometimes you may see a joystick interface too; one that converts from 9-pin Atari-style digital to 15-pin BBC analogue. I don't know how well those work, it probably depends on the game what kind of controller it expects. I suppose an interface to fake a digital signal as a "full throttle" analogue signal wouldn't be too hard, but I reckon you'd like to be able to use the modified joystick fully in analogue mode.

Hi. A company called Bud made a 9 pin to 25 pin joystick adapter for the beeb. I've got one somewhere so safe I can't find it. I was thinking of knocking up a linear converter with a cuople of op-amps to convert digital button presses to analogue ramp commands, but its a bit tedious though.

 

[NathanAllan]

I have joysticks like that in stock. PM sent.

 

[carlsson]

Too bad the 15-pin game port on PC compatibles isn't pin compatible with the 15-pin analogue input on the BBC Micros. :-D I've actually compared the two and didn't find a single pin corresponding.

 

[NathanAllan]

Too bad the 15-pin game port on PC compatibles isn't pin compatible with the 15-pin analogue input on the BBC Micros. :-D I've actually compared the two and didn't find a single pin corresponding.

DOH! nevermind. I guess I didn't see that part. Mine are all PC compatible.

Nathan

 

[carlsson]

Perhaps not all is lost, if it is possible to reroute some of the pins. I can't tell if the signals are of the same ranges or even type, but since cybertron asked for just potentiometers, it is possible that one could cut apart a PC joystick. However those are so relatively common that one should be able to find one anywhere.

 

[NathanAllan]

Perhaps not all is lost, if it is possible to reroute some of the pins. I can't tell if the signals are of the same ranges or even type, but since cybertron asked for just potentiometers, it is possible that one could cut apart a PC joystick. However those are so relatively common that one should be able to find one anywhere.

Right. If I know the pinout, what tolerances the BBC is looking for, I can make an adapter for a PC joystick. Best thing would be to have one to compare and then use a db15 breakout box.

This is the type of thing I am up for. I love this stuff. But then again, if I can do it, most anyoen here could do it, too. I will be happy to release all the final results if it's needed.

Nathan

 

[carlsson]

I have uploaded an image I found on page 432 of "The Advanced User Guide for the BBC Microcomputer" (see http://www.bbcdocs.com for more documentation). I don't know if it makes very much sense, but at least one gets a hint about the pinout.



It should be compared with the PC gameport. More than so I don't know.

Pin BBC     PC
--------------
 1  +5V     +5V
 2  GND     /B1
 3  GND     X1
 4  CH3     GND
 5  AnGND   GND
 6  GND     Y1
 7  CH1     /B2
 8  AnGND   +5V
 9  LPSTB   +5V
10  PB1     /B4
11  VREF    X2
12  CH2     MIDITXD
13  PB0     Y2
14  VREF    /B3
15  CH0     MIDIRXD

 

[cybertron]

I have uploaded an image I found on page 432 of "The Advanced User Guide for the BBC Microcomputer" (see http://www.bbcdocs.com for more documentation). I don't know if it makes very much sense, but at least one gets a hint about the pinout.



It should be compared with the PC gameport. More than so I don't know.

Pin BBC     PC
--------------
 1  +5V     +5V
 2  GND     /B1
 3  GND     X1
 4  CH3     GND
 5  AnGND   GND
 6  GND     Y1
 7  CH1     /B2
 8  AnGND   +5V
 9  LPSTB   +5V
10  PB1     /B4
11  VREF    X2
12  CH2     MIDITXD
13  PB0     Y2
14  VREF    /B3
15  CH0     MIDIRXD

Hi

I recently hacked the 9 way D off an old amiga Quickshot joystic and rewired it to a 15 way D and plugged it into the beeb. It worked but it was too slow. I had to wire the two fire buttons in parallel to free up the second fire button wire to carry the analogue ground signal. The pots in the Quickshot are linear slider ones. I might be able to bias out some of the resistance with extra resistors, to make it more sensitive.

 

[per]

I have uploaded an image I found on page 432 of "The Advanced User Guide for the BBC Microcomputer" (see http://www.bbcdocs.com for more documentation). I don't know if it makes very much sense, but at least one gets a hint about the pinout.



It should be compared with the PC gameport. More than so I don't know.

Pin BBC     PC
--------------
 1  +5V     +5V
 2  GND     /B1
 3  GND     X1
 4  CH3     GND
 5  AnGND   GND
 6  GND     Y1
 7  CH1     /B2
 8  AnGND   +5V
 9  LPSTB   +5V
10  PB1     /B4
11  VREF    X2
12  CH2     MIDITXD
13  PB0     Y2
14  VREF    /B3
15  CH0     MIDIRXD

This is the one from the PC, and to be honnest, it should be piece of cake to make a converter IF the Ohm values are the same (0-100k Ohm):

 

[carlsson]

This is what the book says:

The analogue to digital converter (ADC) chip provided in the BBC microcomputer is a 10 bit integrating converter. It has four input channels which can be selected under software control. By applying a voltage of between 0 volts and Vref to the channel inputs, a 10 bit binary number will be generated which is directly proportional to the applied voltage. For example applying a voltage Vref/2 would produce a 10 bit value of approximately 511. Vref itself corresponds to about 1023.

It is funny it mentions what value Vref will read out, but not which voltage it equals. I would suppose 5V? In that case, what range would the potentiometer need to be to vary the voltage from 0 to 5V?​

 

[cosam]

It is funny it mentions what value Vref will read out, but not which voltage it equals. I would suppose 5V? In that case, what range would the potentiometer need to be to vary the voltage from 0 to 5V?

Is this a trick question? ;-) The potentiometer is essentially functioning as a voltage divider ranging from 0V (analogue ground) and Vref, so you could actually achieve the voltages using any potentiometer which starts at zero. The nominal value of Vref therefore isn't very interesting.

 

[bubbo]

Hi Cybertron
Been searching the web for some info on a machine I have and I have found that you
have one as well.

RADE WATSON Z80 cp/m machine .

My question to you is DO YOU HAVE ANY SYSTEM DISKS.
or can you direct me to somewher that I can download them.
Oh by the way did you get your analogue joysticks.
I had at some time dozens of a joystick guts ie 2 potentiomemters and chassis ,
I think they were for radio control systems .
If I find themn we could do a deal.

Brian
brianjp50@tiscali.co.uk