MBPII Modification

[Shift838]

14 hours ago, Gary from OPA said:

Hmm. Not sure about the clock speed part.

 

But the ama/amb/amc address decode will work in both TI99 And geneve as the flexcable interface pulls those 3 extra address lines high.

I’m thinking a dip switch for the clock slowdown for the Geneve is going to be needed.

[+InsaneMultitasker]

On 8/21/2024 at 4:17 PM, Shift838 said:

another thing I have been racking my brain about is if converting the ADC for inputs 0-7 is only needed then why was all the other signals connected to the 34-position card edge connector instead of just inputs 0-7, ground and +5v?  There are 12 other signals connected to the card edge connector that go to either U13 or U14.  Why would those be needed if we only need inputs 0-7, ground and +5v?  If those other signals are needed then the RCA jacks I am thinking won't work and I'll need just a cable header to be used of some sort.

The 12 signals should correspond to the 2 x 6-bit digital outputs.  The board you got from Dan does not appear to have the needed modification to enable those outputs. 

[Shift838]

14 hours ago, InsaneMultitasker said:

The 12 signals should correspond to the 2 x 6-bit digital outputs.  The board you got from Dan does not appear to have the needed modification to enable those outputs. 

I figured that after reading the documentation.  It needs the extra LS08 chip.  No where in the documentation though does it say anything about how to hook something up to pull the signals.  There is a test circuit that shows the resistor ladder to create, and it is hooked up to 5v, GND and inputs 0-7.  So, I am thinking the other signals on the other side of the card edge is not used.  If that is correct, then I should be able to use 8 RCA jacks for the input signals with the ground hooked up to the RCA shield and the input line of the ADC IC hooked to each of the RCA jacks.  Then the card would have inputs 0-7, 1 for each rca mono jack.

 

 

[+InsaneMultitasker]

6 hours ago, Shift838 said:

I figured that after reading the documentation.  It needs the extra LS08 chip.  No where in the documentation though does it say anything about how to hook something up to pull the signals.  There is a test circuit that shows the resistor ladder to create, and it is hooked up to 5v, GND and inputs 0-7.  So, I am thinking the other signals on the other side of the card edge is not used.  If that is correct, then I should be able to use 8 RCA jacks for the input signals with the ground hooked up to the RCA shield and the input line of the ADC IC hooked to each of the RCA jacks.  Then the card would have inputs 0-7, 1 for each rca mono jack.

 

 

0-7 are inputs. The 12 bits are outputs.  Not sure why you are saying the other signals are not used.  

[Shift838]

1 hour ago, InsaneMultitasker said:

0-7 are inputs. The 12 bits are outputs.  Not sure why you are saying the other signals are not used.  

What I was saying is that there are no examples of using the outputs in the manual, and the ADC test circuit only appears to hook up to the inputs.  So, I am trying to figure out how the outputs should be taken in account for access on the board.  I'm thinking I can use the RCA jacks just for the inputs and have a header that has inputs and outputs annotated for use with jumper wires or I can just slap a DB25 female on the end of the board and let the users custom make their own cables and maybe a couple of RCA jacks for a couple of inputs that could be selected by a dip switch or use of a jumper wire.

 

For some reason I am having a hard time deciding the best course of design for easy access to the inputs and outputs for the ADC.

 

Thoughts?

 

 

Edited August 24 by Shift838

[Shift838]

I've decided to use a DB25 Female to map all the input, output, gnd and VCC signals to.  Along with that I will have a complete 26 pin header if one wants to use jumper wires.  I may go ahead and put a couple of RCA jacks if they will fit and an additional header pin for the RCA jacks to be able to jump an ADC input over to the respective RCA jack.  I think this will give users multiple options to be able to use the input and output signals.

 

 

[+InsaneMultitasker]

I looked through my papers again this morning.  I don't have anything more related to the MBPII from back then that would feed into this discussion.  It seems to me you are on a good path to make the card usable via multiple connection paths.

 

As for examples, all that I remember playing with was sound output which I believe was a pair of resistor networks with an RCA jack connected to each of them.  Basically, two 6-bit Digiports via the MBPII.  If you wanted to add RN and RCA jack for each, the user could use your header pins to push sound output via the RN.  I will say that there wasn't much interest in the sound output, I suppose SoundFX and DigiPort already filled that niche.  I also don't recall interest in the digital outputs, probably for the reason similar to what you stated: there aren't any examples. Even the MBP manual's examples for the analog side are pretty anemic in their details.   It might be helpful to hear from those who are using and/or interested in a new board.