Playing with I2C OLEDs

Massimo

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Apr 5, 2026, 6:22:14 AM (4 days ago) Apr 5

to RC2014-Z80

The applications are still a bit rough but if anyone wants to play with it I'm attaching them.

One is for the PCF8584 based modules and the other for bit-banged I2C like the SC608 while the DAT files are the images I had Claude convert to be displayed.

If you have a PCF8584 module mind that base address and clock match (CPU_CLK should be PCF_CLK and it's the crystal on the board while 8 seems to work fine then using the system 7.3728 MHz clock even if it's slightly lower)

I2COLED.COM.TXT

PCFOLED.COM.TXT

ROMWBW.DAT

I2COLED.ASM

PCFOLED.ASM

OLEDTEST.DAT

RC2014.DAT

Bill Shen

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Apr 5, 2026, 10:30:48 AM (4 days ago) Apr 5

to RC2014-Z80

Very cool! Have you done a speed comparison between PCF8584 and bit-bang I2C?

Bill

Massimo

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Apr 5, 2026, 11:35:02 AM (4 days ago) Apr 5

to RC2014-Z80

I haven't but playing with both I didn't really notice any real difference to be honest

Alan Cox

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Apr 5, 2026, 12:32:59 PM (4 days ago) Apr 5

to rc201...@googlegroups.com

On Sun, 5 Apr 2026 at 16:35, Massimo <ran...@gmail.com> wrote:

I haven't but playing with both I didn't really notice any real difference to be honest

Matches my experiences - PCF8584 is great if you need to do interrupt driven I2C bus in the background but if your CPU is totally free anyway then it's not much use.

In the other direction though (PCF8584 and Z80 as slave) it's a different story usually because you want to be getting on with tasks until the i2c pokes you.

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