"sidegrade" your H17 board

[glenn.f...@gmail.com]

Not sure if it’s an upgrade so I’ll call it a “sidegrade”. Recall Norberto developed a “super” I/O board combining the functions of the H17, HSFE, H37, H67, and VDIP/USB all into one package. But it wouldn’t fit on a single board, so he used a “piggyback” approach with the H17/USB portion plugging into the 37/67 board:

http://koyado.com/Heathkit/H8-H17-H37-H67-USB.html

 

This was an innovative idea but in practice proved a bit awkward. First of all, it didn’t really save you a backplane slot since the double-board still took up the equivalent of two boards, plus I found myself frequently having to remove the H17 to do something with the 37/67 part.

 

So Norberto decided to re-create the H17/HSFE/USB board as a standalone board:

http://koyado.com/heathkit/New-H8-Website/h8-h17-vdip1-fsb.html

 

I was looking for a relatively simple board to work on and I’ve been playing with H17 stuff lately so I decided to “sidegrade” my piggyback H17 board into a full stand alone board (these are  available from Todd as “H8 H17 Controller v2.1”)

 

Since the new board is 90% identical to the old one I was able to reuse all the chips and I also rescued/repurposed some of the more valuable soldered on components as well. Norberto took the opportunity to make a few enhancements like LED indicators for monitoring drive access and other status conditions, plus there’s now a TL7757 which I believe is to help stabilize power startup for the ATTINY micro that runs the HSFE code.

 

Norberto: I made note of some bugs in the BOM and will get those to you for update.  The new board requires a few additional ICs (an LS540, LS02, and a GAL plus an LS541 to drive the indicator LEDs).  Given the number of LEDs on the board Norberto chose to use a resistor pack for the LED current limiters, which I don’t have so for now the whole LED indicator section is unfinished. Here’s what the board looks like:

 

 

I’ve only done rudimentary initial testing so far, booting HDOS 2 from a legacy H17 drive but that works fine:

 

 

This is with a Z80 (Rev. 2.6) CPU at 2Mhz.  I’ll do more testing but so far so good!

 

Norberto and Todd: thanks for making this “sidegrade” available!  I much prefer it to the piggyback arrangement!

 

• Glenn

 

[Chris Elmquist]

On Monday (10/09/2023 at 01:10PM -0400), glenn.f...@gmail.com wrote:
>
> plus there's now a TL7757 which I believe is to help
> stabilize power startup for the ATTINY micro that runs the HSFE code.

I'm super busy all over the map and as a result, eons behind reading
this list, but I did just see this in Glenn's posting from a month ago.

Is there a startup problem with the ATTINY2313 I used in the HSFE?
I have not heard of such until now.

The "lfuse" being programmed should be 0xff, which chooses a 65ms reset
and "slow rising power". So, it should wait like, forever, before it
comes out of reset.

Is the 5V power domain quite different now where they are being used?

cje
--
Chris Elmquist

[Glenn Roberts]

Hopefully Norberto will weigh in. It was pure guesswork on my part as to why the TL7757 was needed…


Sent from my iPad

> On Dec 5, 2023, at 3:52 PM, Chris Elmquist <chr...@pobox.com> wrote:

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[smb...@gmail.com]

I found a quote of mine from February:

"Norberto, I don't think I ever got back to you on using the brownout detection bits in the HSFE ATTINY to prevent issues when the H8 is started while the Gotek is powered (or vice-versa). Since setting the BOD bits some time back, I haven't experienced any trouble."

Prior to this I had experienced startup problems and after setting the BOD bits, the problems went away.

Scott

[norberto.collado koyado.com]

Issue: Too much voltage leak from the Gotek drive will keep the HSFE ATTINY semi-powered up and will no reset HSFE on H8 power-on. Not an issue with the 3.5” floppy drives.

 

Solutions:

1. The default BODLEVEL needs to be set to 4.3 Volts as there is too much voltage leakage when connecting the GoTek drive.
2. Or insert TL7757 to keep HSFE in reset mode until VCC is above 4.3 volts.
3. Link: http://koyado.com/heathkit/New-H8-Website/download/h8_h17_v_1_0_jumper_definitions%20(1).pdf

 

Steps to reproduce:

1. Power-on Gotek drive
2. Power-on H8
3. HSFE ATTINY is non-operational. 100% repeatable.

 

NC.

 

To view this discussion on the web visit https://groups.google.com/d/msgid/sebhc/22fdb2a7-a00e-4b98-85a8-0cd33339c659n%40googlegroups.com.

[Chris Elmquist]

oh wow. OK. So, the GOTEK is back-powering the AVR through some of the
interface signals. Interesting.

Can't fix that one in the code unless Scott's approach with the brown-out
detection works, so you guys are on the right track.

IMO, some buffering between the AVR and the floppy interface to prevent
such back-powering might be the ideal solution but that's more parts.

cje

On Wednesday (12/06/2023 at 03:35AM +0000), norberto.collado koyado.com wrote:
> Issue: Too much voltage leak from the Gotek drive will keep the HSFE ATTINY semi-powered up and will no reset HSFE on H8 power-on. Not an issue with the 3.5” floppy drives.
>
> Solutions:
>

> 1. The default BODLEVEL needs to be set to 4.3 Volts as there is too much voltage leakage when connecting the GoTek drive.
> 2. Or insert TL7757 to keep HSFE in reset mode until VCC is above 4.3 volts.
> 3. Link: http://koyado.com/heathkit/New-H8-Website/download/h8_h17_v_1_0_jumper_definitions%20(1).pdf
>
> Steps to reproduce:
>
> 1. Power-on Gotek drive
> 2. Power-on H8
> 3. HSFE ATTINY is non-operational. 100% repeatable.
>
> [cid:image0...@01DA27B1.A45BB860]

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>
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--
Chris Elmquist