Front-Panel Booting an ATmega88 Microcontroller

[ledtester]

Has anyone ever programmed a ATmega88 using the parallel interface?

In spite of possible switch bounce this programming can be done with mechanical switches -- just like the Altair and IMSAI 8080 micros were programmed from a front panel.

The link jumps into the video at 6:48...

Front-Panel Booting an ATmega88 Microcontroller -- lftkyro
https://youtu.be/S-2adBkW7Xo?t=6m48s

[westfw]

I built hardware and wrote Arduino code to program ATtiny28s, which is parallel-program-only...
(It might be slightly easier than the m88; IIRC it programs 1 word at a time without "page" issues.)

[Doctorandus_P]

That's a week after the Hackaday article:

https://hackaday.com/2025/10/28/give-atmega88-the-boot-with-this-retro-front-panel/

It used to be quite common to use parallel programming mode to recover from bad fuse settings. In those days there were little programs for an AVR to reset the fuses of another AVR. But for software development connecting some serial interface is much more convenient. I guess parallel can also be quicker, but most of the time is probably spent in waiting for the electrons to seep though the Flash cells.

[cv007]

Has anyone ever programmed a ATmega88 using the parallel interface?

I made a 'fuse buster' long ago which used parallel/hv programming. Its only purpose was to reset fuses to default. I recall the avr had a problem where the ide (WinAvr?) would juggle fuses to get debugwire but you sometimes/somehow ended up losing the ability to do any programming. It could handle all pdip parts at that time- put target in appropriate socket, set a switch to select the target type/socket, turn on and you get an empty/default fused avr. I think the mega164 was used as the brains, and the rs232 ic generated the hv. The serial port was for interactive use and firmware upgrades via bootloader.

I have an old Elenco MM-8000K Micro-Master where you had to use slide switches to initially program it so you could then use the keypad to enter programs. Not much fun, even after the keyboard was functional. Thankfully no need for any of that today, but YouTube channels need content, which is fine.

[amyk]

13 years ago, someone did it with the serial programming interface, although a (much) shorter program:

https://habr.com/en/articles/152052/

[Doctorandus_P]

This last post reminds me of a similar subject, of using a 74hc595 with a few R's and C's and a bit of clever programming. With this you can control the whole thing from a single output pin. A sort of morse code, but with three different pulse widths.

[eblc1388]

This last post reminds me of a similar subject, of using a 74hc595 with a few R's and C's and a bit of clever programming. With this you can control the whole thing from a single output pin.

I did exactly that six years ago. One needs to clocks in series of 1 and 0, then generate a latch pulse.

[Ian.M]

https://www.eevblog.com/forum/projects/latched-shift-register-74hc595-control-via-single-mcu-io-pin/

[westfw]

https://www.edn.com/one-i-o-line-drives-shift-register-with-strobe/