electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
 Forum index » DIY Hardware and Software
CV/Gate control from RS-323 possible?
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [8 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
patrickvf1976



Joined: Aug 08, 2011
Posts: 181
Location: Gig Harbor

PostPosted: Fri Mar 29, 2013 7:12 pm    Post subject: CV/Gate control from RS-323 possible?
Subject description: talking about vintage home computers e. g. TI99/4A
Reply with quote  Mark this post and the followings unread

I have this really old computer, a Texas Instruments TI99/4A and I was wondering if it was possible to send CV and Gate/Trigger signals from it's RS-323 (or is it centronics?) ? Has this been done before? Is it just a matter of splicing CV/Gate jacks to a RS-232/Centronics cable and program the CV/Gate values in Basic (or Assembler) or what would I have to do/build/download to make it work?

Greetings, Patrick
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1234
Location: West Red Spot, Jupiter
Audio files: 158

PostPosted: Sat Mar 30, 2013 4:36 am    Post subject: Reply with quote  Mark this post and the followings unread

My answer off the top is "no" - at least not "easy".

An RS-232 serial port provides an 8 bit data output that is serialized. There are also control signals that are level operated (such as Clear To Send or CTS). CTS might be used as a "gate", but that would depend on what control BASIC or assembly entry points allow. So gate might be pretty easy.

To get a CV you would have to convert the serialized data to a voltage. This would require a DAC (8 bit max since the data stream contains only 8 bits of data) that has a built in UART. I can't remember if I've ever seen something like that. It is true that many if not most DACs these days are serial, but "serial" is a rather broad term. SPI, for example, is a serial protocol, but it will not work with RS232 because SPI is physically clocked by the interface where RS-232 signals have an embedded clocking system.

It is definately possible, but probably requires something like a PIC or other microprocessor (or a lot of CMOS chips) that has a built in UART which can then translate the serial data to parallel so that the data can be presented to a DAC of some kind. And if you're going to use a PIC or other modern microprocessor then using the TI seems a bit moot.

If the TI can support memory mapped I/O, then it should be possible to connect an address decoder and latch to capture 8 bit parallel data and present that to a DAC-08 chip with a small number of parts. Sorry - I don't know the TI-99/4A in particular so I don't know if it has a parallel port - but that would be the easiest way to make CV come out of it.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
richardc64



Joined: Jun 01, 2006
Posts: 614
Location: NYC
Audio files: 25

PostPosted: Sat Mar 30, 2013 5:27 am    Post subject: Reply with quote  Mark this post and the followings unread

JovianPyx wrote:

If the TI can support memory mapped I/O, then it should be possible to connect an address decoder and latch to capture 8 bit parallel data and present that to a DAC-08 chip with a small number of parts. Sorry - I don't know the TI-99/4A in particular so I don't know if it has a parallel port - but that would be the easiest way to make CV come out of it.


No parallel port, but address, data, and some control signals are available, so decoded I/O seems possible. Some "blocks" are already decoded.

http://www.digitpress.com/library/techdocs/99-4a_technical_data.pdf

Old school interfacing.

_________________
"I am endeavoring, ma'am, to create a mnemonic memory circuit... using stone
knives and bearskins." -- Spock to Edith Keeler
Back to top
View user's profile Send private message Visit poster's website
Thomas_Henry



Joined: Jul 24, 2009
Posts: 129
Location: N. Mankato, MN

PostPosted: Sat Mar 30, 2013 10:58 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi,

I actually designed an RS-232 drum interface some twenty-five years ago which provided eight triggers. You'll find it in Electronic Musician, February 1986, pp. 38-40, 42. No microprocessor is required, and the programming was handled by the built-in Basic interpreter of the driving computer. I used a cheapo Radio Shack home computer to fire it.

The main component is the AY-3-1015D UART which used to be available at Radio Shack back then. The circuit could easily be changed to CV output with the addition of a DAC0800.

So, yes, such a rig would be possible without much botheration. However, I think a MIDI interface would be more universal.

Thomas Henry
Back to top
View user's profile Send private message
patrickvf1976



Joined: Aug 08, 2011
Posts: 181
Location: Gig Harbor

PostPosted: Sat Mar 30, 2013 11:58 am    Post subject: Reply with quote  Mark this post and the followings unread

true, but midi doesn't work on old cv/gate machines without an expensive MIDI to CV/Gate device, and since I already have a machine with a general purpose interface, I figured that there might be a dead simple way to control CV/Gate machines with it. Is the UART based circuit in between really necessary? Doesn't the interface already produce a control voltage signal of sorts? Not questioning the necessity of your device, but I was hoping to save a little extra work and use what I have. Do you have a spare one that you might be able to sell for some pocket change?

PS: I just came across this post, which includes a link to a page about a rs-232 to CV/Gate circuit for 486 computers. I wonder if that would work in my TI hmmm...

Last edited by patrickvf1976 on Sat Mar 30, 2013 12:31 pm; edited 2 times in total
Back to top
View user's profile Send private message
JovianPyx



Joined: Nov 20, 2007
Posts: 1234
Location: West Red Spot, Jupiter
Audio files: 158

PostPosted: Sat Mar 30, 2013 12:27 pm    Post subject: Reply with quote  Mark this post and the followings unread

A serial output from a computer has no control voltage capability built into it. There are only digital signals available.

Thomas Henry's idea is about as simple as it gets for using a computer's serial output to generate voltages. Essentially, by tying the UART (with a bit clock) to a DAC0800, he has created a serial DAC. The control voltage created by the DAC0800 will have a resolution of only 8 bits at best.

Gate can come from a flow control signal, but it will likely need to be limited in some way since it can swing from -15 to +15 volts, however, it is a logic signal and should be settable from within the TI computer.

_________________
FPGA, dsPIC and Fatman Synth Stuff

Time flies like a banana.
Fruit flies when you're having fun.
BTW, Do these genes make my ass look fat?
corruptio optimi pessima
Back to top
View user's profile Send private message Visit poster's website
gdavis



Joined: Feb 27, 2013
Posts: 155
Location: San Diego

PostPosted: Sat Mar 30, 2013 12:30 pm    Post subject: Reply with quote  Mark this post and the followings unread

First you're going to have to straighten out your interface question. RS-232 is serial, Centronics is parallel. Two different beasts so you need to decide which you're actually planing to use before going forward.

If it's RS-232 then yes, a UART is necessary to deserialize the data. If it's Centronics no UART is necessary.

Both interfaces are digital - either on or off - so no CV directly from them, you need some sort of DAC.

A parallel port could be used as gates pretty easily, you might need something to adjust the levels or buffer it. It's only 8 bits though, so for CV you'd need some sort of multiplexing scheme.

I don't know what you consider "expensive" but people have made midi-CV/gate with an Arduino board.

_________________
My synth build blog: http://gndsynth.blogspot.com/
Back to top
View user's profile Send private message
patrickvf1976



Joined: Aug 08, 2011
Posts: 181
Location: Gig Harbor

PostPosted: Sat Mar 30, 2013 12:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, I got it back out of the attic and took a good look at it - It seems to be neither RS-232 nor Centronics or if at all it's got to be a proprietary version of it. In the manual it's only called an expansion port. weird. Other ports I found are proprietary joystick, tape and video ports. Oh, what was I thinking - I'm not a programmer nor a technician. I guess I'll be better off getting a MIDI to CV device.
PS: What I consider expensive - with my current budget anything over $50 is out of my league
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: jksuperstar, Scott Stites, Uncle Krunkus
Page 1 of 1 [8 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use