ssd1306 wrong resolution on 128x32 OLED

[mikegleasonjr]

Using this product on Raspberry Pi Zero W using latest stretch:

Adafruit PiOLED - 128x32 Monochrome OLED Add-on for Raspberry Pi
https://www.adafruit.com/product/3527

The image seems wrong using the ssd1306 cmd provided in the package:

./ssd1306 -h 32

Results in:

It only writes to the second half of the screen, with tiny text cut in half.

# even though the display has a height of 32, I tried 64 to see
./ssd1306 -h 64

Results in:

The display is working fine with their official python library: https://github.com/adafruit/Adafruit_Python_SSD1306/blob/master/Adafruit_SSD1306/SSD1306.py

The Adafruit 128x64 OLED Bonnet for Raspberry Pi is working fine with periph (https://www.adafruit.com/product/3531):

[maruel]

Interesting. Can you try changing this line:
https://github.com/google/periph/blob/master/devices/ssd1306/ssd1306.go#L207
to 0xDA, 0x02, ?

[mikegleasonjr]

@maruel nope, same problem.

I don't know if it is relevant/interesting or not but... if I try with -h 32 on the 128x64 display, it displays on the bottom half of the screen (like 1st screenshot, but on the 128x64 device)

[mikegleasonjr]

@maruel I picked up the device again and found the problem this time.

I looked at how the device was initialized with the adafruit python library (https://github.com/adafruit/Adafruit_Python_SSD1306/blob/master/Adafruit_SSD1306/SSD1306.py#L309). I found a mismatch here https://github.com/google/periph/blob/master/devices/ssd1306/ssd1306.go#L207.

So I replaced...

0xDA, 0x12, // Set COM pins hardware configuration; see page 40

with...

0xDA, 0x02, // Set COM pins hardware configuration; see page 40

And now the display is working properly:

There is no public interface to send commands directly to the display, what do you propose to make something flexible so I can make it work?

[mikegleasonjr]

@maruel I feel silly, that was your proposed diagnosis the first time!

[mikegleasonjr]

I found out how to do it:

if err = c.Tx(0x3C, []byte{
    0x00, // I²C transaction has stream of command bytes
    0xDA, // set comm pins
    0x02, // 2
}, nil); err != nil {
    return nil, err
}

I am going to close it now :)

[maruel]

No worries. :) Reopening because this is a bug.

So clearly the COM pins configuration needs to either have more conditions or be made configurable. I think we'll need the later as this really depends on the hardware configuration. :/ Expanding on the doc which isn't that clear;

Bits

• 5 enables top and bottom panel swap
• 4 enables alternative each side instead of using two subpannels

This is coupled with C0/C8:

• C0 means bottom-top
• C8 means top-bottom

It is used to rotate the display.

So we'll need an enum to clarify the above in a way that keeps the rotated functionality working (which I'd prefer if possible).

[maruel]

FTR, I still want to fix this, I just need to figure out the best way to expose the bit.

[maruel]

I'm starting to think about v3, this should be fixed in time for this release, which will likely be in a few months.

[mikegleasonjr]

@maruel thanks! in the meantime I have a workaround so that's great

[mikegleasonjr]

Thank you very much!