An H8 Badge for VCFMW

[Lee Hart]

Let's start a new thread, as we were wandering off-topic in the VCF-East thread.

I'm thinking of making a wearable "badge", intended as an inexpensive kit for people to build at VCFMW in September. It would introduce people to the Heathkit world of kit-building. Here's a "straw man" description.

- 80C85 CPU (since this is a *vintage* computer show)

- 32k RAM at 8-40k

- 32k EPROM, 0-8k with PAM8 (or hex version?), 40-64k with Benton Harbor BASIC

- bit-banged serial port using the 80C85's SID and SOD pins.

- 4x4 keypad using tactile switches

- nine 0.3" 7-segment LED displays.

- a PCB styled like a half-size H8 front panel (about 6"w x 3"h)

- powered by USB-serial adapter, or battery operated with three AAA cells.

- a manual to imitate the Heathkit manuals (probably online to download).

- target parts cost around $20.

I've been scribbling circuits, and think I can do it with about six chips.

- 80C85. OKI seems to be the best source of these on ebay.

- 27C256 EPROM (cheap and easy to get).

- CY7C199 32k "skinny" RAM (because I use them in my other kits).

- 74HC151 address decoder (a 1-chip way to get the funny address map).

- 82C55 to provide three 8-bit I/O port (LED anodes, LED cathodes, read keypad).

- 74LS145 to select LED cathodes and keypad rows.

PAM-8 and BHBASIC would have to patched to run in this minimalist H8 environment, as the keyboard and display mapping won't be the same. Likewise for the bit-banged serial port. I'm guessing BASIC could be stored in high EPROM, and block-moved into RAM to execute. There should be lots of room in high EPROM for other programs as well (like the iconic "your H8 is up and running" demo).

This is just my "brainstorming" so far. I'm not a software guy, so I'll certainly need help to pull this off. Can you help, or think of any improvements? Please let me know what you think!

Lee Hart

Virus-free.www.avast.com

[Joseph Travis]

It's very likely that only the PAM8 monitor ROM will have to be modified for I/O as BHBASIC would be doing it's console and keypad I/O through the ROM.  We'll have to verify that though.  Seems to me there are a couple qwerks about BHBASIC when it starts up... I'll look into it.

Joe

--
You received this message because you are subscribed to the Google Groups "SEBHC" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sebhc+un...@googlegroups.com.
To view this discussion visit https://groups.google.com/d/msgid/sebhc/CAF__8hd%2BHYa23X8u%3DetJKCFzCZvR_rN8%3DTCAM%2BYj_0fWrExsbQ%40mail.gmail.com.

[Douglas Miller]

I'll throw in my "free" software advice. The 8085 SID/SOD as serial does not make a good console. The challenges of receiving characters asynchronously (unexpectedly, as required for typing) requires near-constant CPU monitoring of SID. If it is only used for output, say a printer, that is easier to manage (XON/XOFF handshake is  still a challenge).

[Randy E (OoMOR)]

Lee/All,

Would these badge kits be available to those of us that can't make it to VCFMW?

Thanks, Randy

[Lee Hart]

Doug: I agree that SID by itself is not a responsive serial input. The program would have to be looping on a RIM instruction to keep reading SID to detect a START bit.

However, the serial input can also be wired to trigger an interrupt. Josh Bensadon did this on the software for my Z80 Membership Card and 8080  Altaid kits. The program can then be doing anything. When a serial character comes in, its START bit sets SID low *and* triggers an interrupt. The interrupt handler reads the bits on SID (ignoring further interrupts). When finished, the interrupt handler puts the character in a buffer, enables interrupts, and returns to the main program.

Randy: Yes, of course they would be available to anyone that wants one. Like Norberto etc. do with their boards, I expect that we'd try to get some idea of how many PCBs and parts to order. They'd get sold on a first-come first-serve basis. If there was enough interest, we could make additional batches.

Virus-free.www.avast.com

--

You received this message because you are subscribed to the Google Groups "SEBHC" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sebhc+un...@googlegroups.com.

To view this discussion visit https://groups.google.com/d/msgid/sebhc/7ce72d58-2d8f-4654-939d-42701944d88dn%40googlegroups.com.