[Coco] MC-10 Questions...

[peak at mail.polarcomm.com]

Here's an idea! Steal the pot from an actual joystick and 
replace the fuelguage pot with float inside the fuel tank 
with the one you stole from the joystick.
That coulc work but I wouldn't want to do it!!
Eric


---- Original message ----
>Date: Sun, 08 Aug 2004 13:40:29 -0400
>From: jdaggett at gate.net  
>Subject: Re: [Coco] MC-10 Questions...  
>To: CoCoList for Color Computer Enthusiasts 
<coco at maltedmedia.com>
>
>Mike
>
>Since the joystick porrt measures voltage across a 
resister,you need to know 
>the resistance or the current through the resister. 
>
>To setup the joystick port to read a resistance value you 
need to measure the 
>voltage drop across an unknown resister that has as its 
current source a known 
>constant current.
>
>The real problem is that the Coco3 does not really measure 
the voltage. It 
>programs a middle value, between 0 and 63,  into a DAC and 
the joystick port 
>and the output of the DAC are fed into a comparator. To 
determine the exact 
>position, the DAC values are adjusted until the comparator 
output changes 
>state. Kind of an indirect method. Besides the six bits in 
the DAC are woefully 
>very inaccurate.
>
>james
>  
>
>On 7 Aug 2004 at 22:36, KnudsenMJ at aol.com wrote:
>
>From:           	KnudsenMJ at aol.com
>Date sent:      	Sat, 7 Aug 2004 22:36:32 EDT
>Subject:        	Re: [Coco] MC-10 Questions...
>To:             	coco at maltedmedia.com
>Send reply to:  	CoCoList for Color Computer Enthusiasts 
><coco at maltedmedia.com>
>	<mailto:coco-
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>
>> In a message dated 8/7/04 9:09:35 PM Eastern Daylight Time,
>> farna at att.net writes:
>> 
>> > The other gauges, fuel level, engine temp, oil pressure, 
and
>> > possibly volts 
>> (
>> > haven't figured out how to do that one yet, the other 
three are
>> > simple variable resistances that I know the ranges for) 
could be
>> > slower. The oil pressure will have a back-up warning 
light. The
>> > numbers displayed will have to be on a graphics screen 
to be big
>> > enough to easily see. I'd probably use 
>> a 
>> > mechanical hour meter under the hood and forget mileage, 
unless I
>> > can find 
>> a 
>> > stand alone odometer instead of an hour meter. 
>> >  
>> >  Heck, I've forgot how I measured resistance now!! I 
remember using
>> >  the 
>> > joystick D/A inputs, but that's all. Got the idea from a 
game that
>> > used a series of push buttons for a Jeapordy style 
buttons connected
>> > to one port. 
>> I 
>> > think each button had a different resistance and the 
CoCo could tell
>> > which button was pressed. Might have to have the gauges 
work in 5 or
>> > 10 unit increments, but would be close enough. 
>> 
>> I think you're forgetting something -- that the Coco's 
joystick inputs
>> measure Volts, period.  Resistor hookups are just voltage 
dividers of
>> a known external reference voltage, into a dependent 
voltage that
>> feeds to the A/D joystick inputs.
>> 
>> To monitor your car's battery voltage, which ranges 
between 12 and 15
>> or so, use a pair of fixed resistors to divide it by 3, so 
that range
>> becomes 4 to 5 V (remember, the Coco joysticks measure 
from 0 to 5 V,
>> no more).
>> 
>> I think a competitor, maybe Apple, used a similar scheme 
to the
>> Coco's, but had one of the resistors built into it, so the 
joystick
>> was just a variable resistance.  Not nearly as flexible as 
our Coco
>> (but then, what was/is?) --Mike K.
>> 
>> 
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