[N8VEM: 15894] Cassette Interface Switches

[Wayne Warthen]

H Folks,

I finally got a chance to put together my Cassette Interface board.

I am struggling with understanding SW1 and SW2. I presume these are the
two switches that are referred to as the record switch and the playback
switch. If so, which is which? And what do the switch positions mean?

I have studied the schematic and am not understanding the use of SW1 and
SW2 at all...

SW1 seems to bridge TXD and RXD. What is the reason for doing that?

SW2 seems to bridge RTS and CTS. Again, what is the purpose of doing so?

The "super-simple cassette interface" article indicates that the clock
signals should be bridged during record. But I see no way to do that with
the setup of SW1 and SW2.

Any help would be appreciated.

Thanks,

Wayne

[brizza]

Hi Wayne,
SW1 is program load and SW2 is program save.
David Giles' Rom DG_PPIDE_110918.zip (found on the Wiki) supports the CI
board and has detailed instructions on it's use.
I had some difficulties adapting the "super-simple cassette interface" to
the ECB design and ended up using one switch to load and the other to save
but not a combination of both as outlined in the magazine article.
Without doubt the board needs to be revised but it works perfectly in it's
current form.
Good to see someone else has built one ! :-)
Kind Regards,
Nik

Post by Wayne Warthen
H Folks,
I finally got a chance to put together my Cassette Interface board.
I am struggling with understanding SW1 and SW2. I presume these are the
two switches that are referred to as the record switch and the playback
switch. If so, which is which? And what do the switch positions mean?
I have studied the schematic and am not understanding the use of SW1 and
SW2 at all...
SW1 seems to bridge TXD and RXD. What is the reason for doing that?
SW2 seems to bridge RTS and CTS. Again, what is the purpose of doing so?
The "super-simple cassette interface" article indicates that the clock
signals should be bridged during record. But I see no way to do that with
the setup of SW1 and SW2.
Any help would be appreciated.
Thanks,
Wayne

[Wayne Warthen]

Thanks for the quick response Nik, this should get me going.. I will
review David Giles' instructions as well. No doubt, it is working -- I
just didn't follow the circuitry.

With any luck, I will soon integrate support for it into RomWBW.

Thanks,

Wayne

Post by brizza
Hi Wayne,
SW1 is program load and SW2 is program save.
David Giles' Rom DG_PPIDE_110918.zip (found on the Wiki) supports the CI
board and has detailed instructions on it's use.
I had some difficulties adapting the "super-simple cassette interface" to
the ECB design and ended up using one switch to load and the other to save
but not a combination of both as outlined in the magazine article.
Without doubt the board needs to be revised but it works perfectly in it's
current form.
Good to see someone else has built one ! :-)
Kind Regards,
Nik

Post by Wayne Warthen
H Folks,
I finally got a chance to put together my Cassette Interface board.
I am struggling with understanding SW1 and SW2. I presume these are the
two switches that are referred to as the record switch and the playback
switch. If so, which is which? And what do the switch positions mean?
I have studied the schematic and am not understanding the use of SW1 and
SW2 at all...
SW1 seems to bridge TXD and RXD. What is the reason for doing that?
SW2 seems to bridge RTS and CTS. Again, what is the purpose of doing so?
The "super-simple cassette interface" article indicates that the clock
signals should be bridged during record. But I see no way to do that with
the setup of SW1 and SW2.
Any help would be appreciated.
Thanks,
Wayne

[Vince Mulhollon]

Post by Wayne Warthen
With any luck, I will soon integrate support for it into RomWBW.

Is there a way to treat the cassette interface at the CPM level as kind of
a universal serial port, that could have the cassette modem, or perhaps
something else attached? I missed CPM back when it was new, so I'm a
little fuzzy on what it can, or cannot, do at the OS level. I'm sure I
COULD write a complete UART driver in mbasic using IO output and input
commands, but I'm hoping to avoid that level of "fun"... In summary I'm a
totally fuzzy on the whole "on a CPM box, this is how you send to the
serial port in MBASIC" other than implementing an entire UART driver at the
bare IO port level.

I have grandiose and unrealistic plans in my limited spare time to kitbash
the cassette interface into a MIDI. Physically its simple, a couple cheap
DIN sockets, probably inline sockets on very short cables to attach to real
off the shelf standard MIDI jumpers and onto the synth input line.
Electrically its really simple, a couple optos and resistors and a new
oscillator for the UART (from memory a 2 mhz UART osc instead of 1.8432 mhz
with a 64 overall UART division sounds about right). Once you can
controllably squirt out arbitrary bytes, basic MIDI protocol is really
simple, just little 3 byte packets and all that to turn notes on and off
and all that. There are complications if you want to do "everything", but
if you just want to make noise, midi is a pretty simple protocol. Then
again a cheap old keyboard with an "in" being used as a synth probably
doesn't support "everything" anyway. The very cheapest keyboards only have
"outs" not "ins" so that makes it more exciting. I'm thinking playing .MID
files might be a very long term goal and stable tempo and maybe even drive
bandwidth will be an issue for large files. A very realistic goal would be
the worlds second most elaborate Westminster chimes via cooperation with
the onboard RTC.

You can have a lot of fun with other "things" attached to a serial port
other than a cassette interface. I have an old serial printer somewhere,
and a some external telephone modems in the pile. They'd need a level
shifter from TTL to RS232 levels no big deal. I have an old X-10 interface
floating around too, as I recall the line protocol was pretty simple for
those devices, so I could turn things on and off. Also I think hooking up
a $50 off the shelf GPS NEMA sender to a RS-232 port would be a hilariously
overcomplicated way to very accurately set the realtime clock chip. I also
have innumerable RS-232 compatible machines available ranging from digital
machinist calipers to multimeters to old HP calculators, all of which I
could do pretty crazy stuff with, given an available serial port.

[Wayne Warthen]

Hi Vince.

Well, I am not well versed in MBASIC. However, I would assume it has some
way to talk to the PTR and PUN devices in CP/M. That would be the simplest
way to read/write the serial port on the Cassette Interface board. You
will need a BIOS that supports the Cassette Interface at PTR/PUN. There is
an existing BIOS by David Giles that does this. Once RomWBW supports it
(soon), you can do it with that firmware as well.

As you probably know, you will need to adjust the P5 jumpers on the
Cassette Interface to switch it between cassette and RS-232 modes.

I am not sure if I am answering your questions exactly, but if not, just
clarify what you need to know. I would be happy to hear of any progress
you make on this project.

Thanks,

Wayne

[brizza]

Cool :-)

Nik

Post by Wayne Warthen
Thanks for the quick response Nik, this should get me going.. I will
review David Giles' instructions as well. No doubt, it is working -- I
just didn't follow the circuitry.
With any luck, I will soon integrate support for it into RomWBW.
Thanks,
Wayne

Post by brizza
Hi Wayne,
SW1 is program load and SW2 is program save.
David Giles' Rom DG_PPIDE_110918.zip (found on the Wiki) supports the CI
board and has detailed instructions on it's use.
I had some difficulties adapting the "super-simple cassette interface" to
the ECB design and ended up using one switch to load and the other to save
but not a combination of both as outlined in the magazine article.
Without doubt the board needs to be revised but it works perfectly in
it's current form.
Good to see someone else has built one ! :-)
Kind Regards,
Nik

Post by Wayne Warthen
H Folks,
I finally got a chance to put together my Cassette Interface board.
I am struggling with understanding SW1 and SW2. I presume these are the
two switches that are referred to as the record switch and the playback
switch. If so, which is which? And what do the switch positions mean?
I have studied the schematic and am not understanding the use of SW1
and SW2 at all...
SW1 seems to bridge TXD and RXD. What is the reason for doing that?
SW2 seems to bridge RTS and CTS. Again, what is the purpose of doing so?
The "super-simple cassette interface" article indicates that the clock
signals should be bridged during record. But I see no way to do that with
the setup of SW1 and SW2.
Any help would be appreciated.
Thanks,
Wayne

[Wayne Warthen]

Just a quick follow-up here to let everyone know that I got my Cassette
Interface board working this weekend. Support for this board in RomWBW
checked out in the latest beta version posted on the Wiki. There is a new
pre-built ROM called N8VEM_ci.rom for this; although, it probably makes
more sense to enable the support in whatever build is best for your system.

I remain somewhat perplexed by the toggle switches on this board. I have
done all my testing with the switches off (down). Recording and playback
all work perfectly. Nice board Nik! Very fun to use PUN: and RDR: devices.

Thanks!

Wayne

Post by Wayne Warthen
Thanks for the quick response Nik, this should get me going.. I will
review David Giles' instructions as well. No doubt, it is working -- I
just didn't follow the circuitry.
With any luck, I will soon integrate support for it into RomWBW.
Thanks,
Wayne

Post by brizza
Hi Wayne,
SW1 is program load and SW2 is program save.
David Giles' Rom DG_PPIDE_110918.zip (found on the Wiki) supports the CI
board and has detailed instructions on it's use.
I had some difficulties adapting the "super-simple cassette interface" to
the ECB design and ended up using one switch to load and the other to save
but not a combination of both as outlined in the magazine article.
Without doubt the board needs to be revised but it works perfectly in
it's current form.
Good to see someone else has built one ! :-)
Kind Regards,
Nik

Post by Wayne Warthen
H Folks,
I finally got a chance to put together my Cassette Interface board.
I am struggling with understanding SW1 and SW2. I presume these are the
two switches that are referred to as the record switch and the playback
switch. If so, which is which? And what do the switch positions mean?
I have studied the schematic and am not understanding the use of SW1
and SW2 at all...
SW1 seems to bridge TXD and RXD. What is the reason for doing that?
SW2 seems to bridge RTS and CTS. Again, what is the purpose of doing so?
The "super-simple cassette interface" article indicates that the clock
signals should be bridged during record. But I see no way to do that with
the setup of SW1 and SW2.
Any help would be appreciated.
Thanks,
Wayne