chan@duke.UUCP (Michael G. Chan) (02/20/85)
Baud rate is the number of changes per second. Thus 9600 baud can transmit
at 19200 bits per second if each frequency transmitted can represent 2 bits
of information.
e.g. frequency 1 encodes 00
2 01
3 10
4 11
then a 9600 baud can transmit 19200 bits of information. So it is possible
to have RS232 talk to MIDI if somebody can come up with such a protocol.
How about using RS422? It is standard on a Macintosh and as far as I know,
it can handle serial communication well beyond 32Kbps. Any suggestion?
I bring this up just because I have one myself and would like to make use
of it.
Anybody out there know if it is possible to upgrade a Poly61 to be MIDI
equipped? Or simply does it worth it? The sound is great but since it
does not has velocity sensitive keyboard, it will not be able to generate
these MIDI commands for transmission anyway...
Thanks in advance for any information you may suggest.
Michael Chan
{...!decvax!mcnc!duke!chan}markmc@ncrcae.UUCP (Mark McCulley) (02/22/85)
~From ncsu!mcnc!duke!chan Wed Feb 20 15:25:53 1985 ~Subject: Baud vs bps and more ~Baud rate is the number of changes per second. Thus 9600 baud can transmit ~at 19200 bits per second if each frequency transmitted can represent 2 bits ~of information. ~then a 9600 baud can transmit 19200 bits of information. So it is possible ~to have RS232 talk to MIDI if somebody can come up with such a protocol. 9600 baud is 9600 characters per second. The bit rate would be ten times that or 96000 (8 data,one start,one stop). RS232 *is* a protocol. MIDI 1.0 specifies a baud rate of 31.25k baud, or 31250 characters per second. The problem is, this rate is not a standard with any computer systems (that I know about). To interface RS232 to MIDI would require a semi-intelligent buffer, fairly fast too. ~How about using RS422? It is standard on a Macintosh and as far as I know, ~it can handle serial communication well beyond 32Kbps. Any suggestion? ~I bring this up just because I have one myself and would like to make use ~of it. I've thought about this some and there seems to be two approaches. One would be with a Appletalk-MIDI device. The other would involve changing the baud rate on one channel of the DUART. I dont' know if the MAC 68000 would be 'real time enough' as it has to handle memory refresh and the video refresh. mark @.../decvax/mcnc/ncsu/ncrcae/markmc
david@daisy.UUCP (David Schachter) (02/25/85)
In article <5447@duke.UUCP> chan@duke.UUCP (Michael G. Chan) writes: >then a 9600 baud can transmit 19200 bits of information. So it is possible >to have RS232 talk to MIDI if somebody can come up with such a protocol. > >How about using RS422? It is standard on a Macintosh and as far as I know, >it can handle serial communication well beyond 32Kbps. Any suggestion? 1.) I hope you are not suggesting that RS-232 can support multiple bits per Baud! The RS-232 standard provides only two signal levels: Mark and Space. These are akin to zero and one. (Or one and zero, depending on your receiver's view of polarity.) I do not believe you can support anything more than simple binary encoding if you only have two signal levels. Thus, for RS-232 connections, a Baud can be interpreted the same as a bit per second. You can't pump 19.2 kbps down a 9600 Baud RS-232 link, I think. 2.) Also, while the RS-232 standard generally applies up to 9600 bps, many people have had luck pushing it quite far past that. We all know that 19.2 kbps is frequently done and DEC has been selling the DECTape-II drive for quite a while running at 38.4 kbps over RS-232-like lines. Any good UART chip can handle 38.4 kbps although you may have to jury rig the clock input since not all clock generators can generate a 38.4 kHz clock, especially at a x4 or x16 rate (which you often use with UARTs to improve signal reception reliablity for reasons too technical to go into here.) What you get with RS-422 is the ability to send a fast signal farther, to adhere to a standard which provides for data rates over 9600 bps, and, if you really want to do it right, to spend more money. Why? Well, RS-422 has a bigger, more expensive connector. It has more wires. And almost no one uses it (no one I know, anyway.) Stick with RS-232 unless you need the extra distance and higher speed of RS-422. [The above does not necessarily represent the views or policies of Daisy Systems Corporation, its employees, or subsidiaries. The opinions expressed herein are the sole responsibility of the author, who has no sense of humor.] {Man walks into a bar. Bounces right off.}