H8-MULTI-IO BOARD.

[norberto.collado koyado.com]

Attached the new H8-Multi-IO board. It includes the following:

 

1. DSRTC time clock
2. 20 ma support for TTY terminals
3. USB serial support
4. I2C support
1. OLED Display Support
2. QWIIC devices support
5. UART High Speed clocks (3.6864MHz and 1.8432MHz)
6. 4x UARTS (PLCC44)
7. VDIP1 support
8. USB Printer support under HDOS.
9. UARTS Ports jumper selectable.

 

Please review attached schematic and provide feedback.

 

Thanks,

Norberto

[Joseph Travis]

Norberto,

I'm still going over it and will try to get back to you tonight or tomorrow.

BR,

Joe 

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[norberto.collado koyado.com]

Thanks!

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From: se...@googlegroups.com <se...@googlegroups.com> on behalf of Joseph Travis <jtravi...@gmail.com>
Sent: Saturday, March 28, 2026 1:40:35 PM
To: se...@googlegroups.com <se...@googlegroups.com>
Subject: Re: [sebhc] H8-MULTI-IO BOARD.

 

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[Joseph Travis]

OK Norberto,  I like it!  You packed A LOT of functionality into this design!  I do have some comments / suggestions:

1 - Thanks for adding the jumper selectable I/O addressing for the UARTs.  The jumper position you have marked as N/C should be changed to OFF.  That position is for the interrupt jumper, if the port isn't using interrupts.

2 - I see that two of the UARTs are using the 74LS03 while the other two are using the 74LS1005.  For the sake of consistency (and good form) I suggest using the 74LS03 strictly for the interrupt outputs from each UART and moving it over next to the interrupt jumper blocks.  Replace the 74LS1005 with a 75232 to be used for the RS-232 handshake lines for each UART.  This way, you're ensured to have the proper signal level.

3 - I'm a little surprised that you don't have a LED for each of the regulator outputs.

4 - I suggest increasing the width of the ground line that passes beneath the mount bracket, at least twice as large than the mounting holes for the bracket.

BR,

Joe

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[norberto.collado koyado.com]

Joe,

 

Thanks for your inputs and added your changes. I had to use the 75188 instead due to the amount of gates needed. The ground will expand as I turned on the ground plane.

 

Updates attached.

 

Thanks,

Norby

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[Joseph Travis]

It looks like the LED placement will interfere with using a USB-Serial adapter on channel 0.

Joe

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[norberto.collado koyado.com]

Board updated and latest files attached

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