NeXT ADB soundboard to NON ADB conversion?

Started by Rob Blessin Black Hole, May 08, 2014, 08:23:08 am

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Rob Blessin Black Hole

Hello NeXT Community : Has anyone out there successfully hacked a NeXT ADB sound board to work with NeXT non adb components? Here is the situation NON adb soundboxes are becoming harder to come by and so are working 4000 and 4000a monitors. I have enough NeXT ADB soundboards in soundboxes to allow for experimenting with a conversion kit.
All NeXT roms before V74 are only usable with Non adb NeXT components
I found this useful thread describing the differences http://newsgroups.derkeiler.com/Archive/Comp/comp.sys.next.hardware/2005-07/msg00009.html
I have a couple guys that are going to help and I'm donating a turbo color with a v74 chip and both adb and non adb components to the project.
Any assistance appreciated , does anyone have the schematics for the pcb sound boards ?
This allows us to use flatpanel monitors with a custom y monitor cable.
Also need to figure out why a cube later model 983 power supply will work and the 152 won't and if there is a way to modify the 152 to become a 983 as this opens up a lot more cube to work with displays!
Ps if you have a cache of non adb soundboxes or NeXT monitors please let me know !
Best regards Rob Blessin
Rob Blessin President computerpowwow ebay  sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community  since 2/9/93

gtnicol

I think the 983 power supply doesn't need the same draw as the 152 to stay on... that's largely it.

For ADB to non-ADB conversion: the ASIC is basically just a multiplexer from what I can see. From probing with an LA, it appears there are 3 subsystems for dealing with the sound, volume, and keyboard/mouse, each with their own internal bus. To take an ADB board and have it work with a non-ADB system, it looks like you'd have to change the  keyboard subsystem and possibly the ASIC as well.

I know from hacking around on the soundbox replacement that the system/ASIC polls the keyboard and mouse, and it seems to basically just take the response and shove it onto the bus to the host (reversed order, so I guess there's a buffer in there). My theory is that the system queries the ASIC for the connected devices at startup, because there is a different sequence of packets at first boot. Probably one part of the response is the connected device(s) type(s), and the v74 ROM can handle a response indicating an ADB or a response handing non-ADB, and that it has code for dealing with the ADB protocol (I think the ADB packets are sent largely unchanged from the ASIC, but I might be wrong... I haven't spent as much time there).

I think there might need to be a change to the ASIC as well because of the difference in the ADB and non-ADB device protocols... ADB is only a single wire.

Rob Blessin Black Hole

It is interesting that you can hot swap a non adb keyboard or mouse or both with out rebooting but with adb components you have to reboot to have them synche.
Rob Blessin President computerpowwow ebay  sales@blackholeinc.com http://www.blackholeinc.com
303-741-9998 Serving the NeXT Community  since 2/9/93

gtnicol

The hot swap is because the ASIC is polling the keyboard/mouse... if you unplug them you can see the packets being sent change (I forget, but there's one which is obviously a reset packet, followed by a read). That's why I think you might have to change the ASIC... the way the ASIC deals with ADB/non-ADB are probably quite different.

I haven't spent a lot of time with ADB peripherals and an LA, so I could be wrong...

barcher174

All,

I'm continuing to work on this, and I don't think the ADB version is using the ASIC at all for the keyboard. More updates to come...

--
Brian

barcher174

So I traced the connection from the data line on the ADB keyboard and it appears to go directly to the 19 pin connector. The non-adb definitely goes into the ASIC before reaching the 19 pin connector. Unfortunately I was not able to get an ADB keyboard to work by directly connecting it. Here's the interesting part though, I've gotten the ADB soundbox to supply 68HZ instead of 72. My theory is that the ASIC can be configured to work with the non-adb with some rework. Too late tonight, but hopefully I can look into it more this weekend.

--
Brian

gtnicol

It may be that the the ADB keyboard support is provided by the motherboard, but I do know that for non-ADB the monitor cable acts as a kind of bus, and the soundboard acts primarily as a means to multiplex the signals to/from the keyboard, audio, and volume controller and motherboard, and that the ASIC contains most of the logic for it. FWIW. ADB keyboards do require a particular BIOS version for at-boot support.

I put an LA on the keyboard etc. and they appear to all have their own protocol that the ASIC works with... usually in the 10s of Hz, while the main bus is 5MHz.

barcher174

So to test my theory I cut the data pin on the adb sound board and patched it directly to pin 5. Works perfectly which tells me the next is controlling adb devices directly. The pins on the ASIC for non adb were tied. By leaving them floating I get 68hz instead or 72. I'm hopeful I can replicate the missing part of the circuit and hook into those pins.

barcher174

So lesson of the day. Don't take conventional wisdom at face value. I decided to take another look today and figure out why I couldn't make the keyboard work correctly directly connected. I was using the pinout I'm sure we've all seen from netbsd.

       10                  1
     _________________________
     \  o o o o o o o o o o  /
      \  o o o o o o o o o  /
       ---------------------
       19                11
+12V
-12V
MON CLK
MON DATA OUT
MON DATA IN
MON PWR SWITCH
NC
VSYNC
HSYNC
VIDEO
+12V
-12V
GND
GND
GND
GND
GND
GND
GND

As it turns out pin 7 -IS- used for ADB. And by that I mean pin 7 is the ADB bus. Directly connected to the NeXT. In other words, if you don't care about sound, the soundbox is entirely unnecessary to have a functioning device. Just provide 5V for the keyboard, hook the power button to pin 6 and the ADB data pin to pin 7. While not the full solution we're looking for, I think this is huge in terms of getting more machines up and running. There are still plenty of mac ADB devices around. So if you have a turbo system with the correct ROM, you now have alternatives to the sound box. I'm pretty excited about this revelation. That much closer to the goal...


EDIT:

I should mention, that makes my previous comment about pin 5 incorrect. I was tired enough to count the pins upside down :D

--
Brian

barcher174

Picture of the process.

Initial prototype

https://www.dropbox.com/s/cn6wgnu17ddtsrj/IMG_0568.jpg

I have a USB hub so I settled on using that for power. I have my custom switch box for my non-adb keyboard so this isn't anything I intend to use long term. If you want an all-in-one solution then you could easily use a 5V voltage regulator.

https://www.dropbox.com/s/xikdmmvycrq4vku/IMG_0569.JPG

https://www.dropbox.com/s/a27fekeoudy8cjh/IMG_0571.JPG

https://www.dropbox.com/s/pujv3z0yz66e4gj/IMG_0572.JPG

--
Brian

jroark

Neat, you could make a very simple vga adb pass through!

gtnicol

What ROM version are you running? I'm assuming a later ROM because earlier ROMs didn't have ADB support. This help to explain why ADB devices had some minor incompatibility issues with some apps too.

barcher174

I'm testing on a turbo color nextstation with the v74 ROM. I haven't verified, but I think the difference is going to be more than software. I won't be surprised if pin 7 is actually left unconnected on the earlier revision logic boards. The up side is I'm feeling pretty confident that a modification to make an adb sound board non-adb compatible is possible. Another thing I was thinking about is that we could use the header on the sound board for VGA instead of the custom Y-cable. It would be a much cheaper solution if you already have the standard monitor cable.

--
Brian

barcher174

I'm just going to let these speak for themselves....

https://www.dropbox.com/s/6cpz880uc5omshy/IMG_0574.jpg

https://www.dropbox.com/s/0bquepf1h02u26n/IMG_0575.JPG

YES. That is an ADB soundboard working with a non-ADB keyboard and mouse. We have a solution. I'll work on a formal write-up with some pics and do a bit more testing to be sure it's stable.

So to sum up:

1) Machines that currently use ADB sound boxes -do not- need the soundbox to function. If you can live without sound you can hook an ADB keyboard directly to pin 7 of the 19 pin connector.

2) If you have an ADB sound board it can be converted to non-adb by cutting a couple traces and adding some passive components.

3) I really need to sleep more. ;)

In addition, regarding the power supply, I highly recommend that the 152 not be modified. I do not believe it is safe to operate without the minimum load. There are 2 options. Create a load on the -12V rail, like I have shown with either a fan or a bulb, or you can also source an appropriately sized 1U ATX power supply and modify it using the instructions I have provided.


--
Brian

jroark

Very nice, can you you use the modified adb soundboard on a non turbo system?