Sampling - Revision history

Polluks: Category

2015-09-10T20:20:36Z

Tlindner: Updated PIA block diagram link

2008-05-17T18:11:07Z

Updated PIA block diagram link

← Older revision		Revision as of 14:11, 17 May 2008
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	Successive Linear Approximation on the Color Computer		Successive Linear Approximation on the Color Computer

	The CoCo uses analog joysticks. A 5 volt signal is sent to the joystick and a smaller voltage is returned depending on the orientation of the stick. The job of reading the joystick is converting that analog voltage to a binary value. During this article it would be advisable to obtain a schematic of the Color Computer. Here is a [http://~~home~~.~~netcom~~.~~com~~/~~~tlindner/Download/CoCoPIAs.pdf~~ detailed] block diagram that will be good enough for this article. Also, a good understanding of the [http://www.google.com/search?q=pia+6821+pdf&ie=UTF-8&oe=UTF-8 Peripheral Interface Adaptor] will help you get the most out of machine language programming.		The CoCo uses analog joysticks. A 5 volt signal is sent to the joystick and a smaller voltage is returned depending on the orientation of the stick. The job of reading the joystick is converting that analog voltage to a binary value. During this article it would be advisable to obtain a schematic of the Color Computer. Here is a [http://tlindner.macmess.org/?page_id=124 detailed] block diagram that will be good enough for this article. Also, a good understanding of the [http://www.google.com/search?q=pia+6821+pdf&ie=UTF-8&oe=UTF-8 Peripheral Interface Adaptor] will help you get the most out of machine language programming.

	Since the CoCo does not have a hardware Analog-To-Digital converter chip, the process it uses is called <i>successive linear approximation</i>.		Since the CoCo does not have a hardware Analog-To-Digital converter chip, the process it uses is called <i>successive linear approximation</i>.

AllenHuffman: removing Category tag, since it should be contained in the Nav template

2008-04-16T15:01:32Z

removing Category tag, since it should be contained in the Nav template

← Older revision		Revision as of 11:01, 16 April 2008
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	Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.		Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.
	~~[[Category:Articles]]~~

AllenHuffman at 05:31, 7 February 2007

2007-02-07T05:31:50Z

← Older revision		Revision as of 01:31, 7 February 2007
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	{{~~NavTop~~}}		{{NavArticles}}

	== Joystick Sampling ==		== Joystick Sampling ==

Auscoco at 05:07, 18 April 2006

2006-04-18T05:07:13Z

← Older revision		Revision as of 01:07, 18 April 2006
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	Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.		Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.
			[[Category:Articles]]

Tlindner: /* Colophon */

2005-05-01T16:32:29Z

Colophon

← Older revision		Revision as of 12:32, 1 May 2005
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	== Colophon ==		== Colophon ==
	As you can see, reading the joystick is quite involved. It is interesting to note that Color BASIC will attempt to read the joystick value ten times but will immediately return once it gets the same value twice from this process. If all ten ~~tried~~ produce different results, the tenth is returned.		As you can see, reading the joystick is quite involved. It is interesting to note that Color BASIC will attempt to read the joystick value ten times but will immediately return once it gets the same value twice from this process. If all ten tries produce different results, the tenth is returned.

			Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.

AllenHuffman: adding NavTop

2005-04-14T19:02:01Z

adding NavTop

← Older revision		Revision as of 15:02, 14 April 2005
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			{{NavTop}}

	== Joystick Sampling ==		== Joystick Sampling ==
	Successive Linear Approximation on the Color Computer		Successive Linear Approximation on the Color Computer

Tlindner: /* Joystick Sampling */

2005-04-12T17:14:49Z

Joystick Sampling

← Older revision		Revision as of 13:14, 12 April 2005
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	# If the sound register is greater than or equal to the joystick value, then you have just discovered the joystick value		# If the sound register is greater than or equal to the joystick value, then you have just discovered the joystick value
	# Increment sound register.		# Increment sound register.
	# Sound register only goes to 64, so stop ~~then~~ you hit 65.		# Sound register only goes to 64, so stop when you hit 65.
	# Go back to step 4.		# Go back to step 4.

Tlindner at 02:52, 9 April 2005

2005-04-09T02:52:50Z

← Older revision		Revision as of 22:52, 8 April 2005
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	STA $FF01 Store value back in CRA.		STA $FF01 Store value back in CRA.

	~~== Compare the sound register to the value from the joystick ==~~
	Read the output from the comparator.		Read the output from the comparator.

Tlindner: /* Increment sound register */

2005-04-09T02:50:29Z

Increment sound register

← Older revision		Revision as of 22:50, 8 April 2005
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	We're done. The value of the joystick is in the sound register. We need to shift the data over two bits to normalize it to 1 thru 64.		We're done. The value of the joystick is in the sound register. We need to shift the data over two bits to normalize it to 1 thru 64.

	DONE LSRB Logical shift right		DONE LSRB Logical shift right
	LSRB Logical shift right		LSRB Logical shift right

	Now subtract one to bring it to 0 thru 63.		Now subtract one to bring it to 0 thru 63.
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	Write value to video memory to see it.		Write value to video memory to see it.

	ORB #$80 Set bit 7 to turn it into a VDG graphic character		ORB #$80 Set bit 7 to turn it into a VDG graphic character
	STA $500 Put value into middle of the 32 collum screen.		STA $500 Put value into middle of the 32 collum screen.
	SWI Return to ZBUG.		SWI Return to ZBUG.
	END		END

	== Colophon ==		== Colophon ==
	As you can see, reading the joystick is quite involved. It is interesting to note that Color BASIC will attempt to read the joystick value ten times but will immediately return once it gets the same value twice from this process. If all ten tried produce different results, the tenth is returned.		As you can see, reading the joystick is quite involved. It is interesting to note that Color BASIC will attempt to read the joystick value ten times but will immediately return once it gets the same value twice from this process. If all ten tried produce different results, the tenth is returned.

← Older revision		Revision as of 16:20, 10 September 2015
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	Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.		Another quirk is BASIC will sample all four joysticks when joystick zero is read. Reading joysticks 1 thru 3 will return values cached during the sampling done when issuing the JOYSTK(0) command.

			[[Category:Programming]]