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SSD1306 display drivers and font rendering

subalpinecircuits.com

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Re: SSD1306 display drivers and font rendering

#21

Post by grmnygrmny2 »

arghwhat wrote: post #14
grmnygrmny2 wrote: post #7

Earlier quoted context omitted.

(author here) I've been pondering this, yeah. I'm currently sharing the I2C bus with a DAC and that's working alright, but the refresh rate issue is enough to make me consider SPI. I know the SPI peripheral supports DMA as well, and the I2C one doesn't (sort of? I know there's "async" transmit now but can't tell if that's really doing DMA)

The I2C peripheral is DMA - a write just queues an operation descriptor in a hardware FIFO, and interrupts fire whenever something exciting happens or the FIFO is drained. The synchronous implementation is just blocking on a condition set by the interrupt handler. But this is exactly the kind of thing the SPI peripheral is meant for. This cannot be said for the I2C peripheral, with its measly fast mode support. Depen…

Ah! That makes sense, thanks!

And yes, the audio data runs over I2S - the chip I’m using just uses I2C for control.

Re: SSD1306 display drivers and font rendering

#22

Post by hadlock »

generj wrote: post #9
arghwhat wrote: post #5

Go for the SPI version, which is the same chip but just s different breakout board. Many ESP32's can only do 400kHz I2C, whereas their SPI peripheral can often do 80 MHz or more (although you wouldn't want to go that fast here). 400kHz sort of works, but if you also want to handle other I2C devices it can easily become a problem.

I2C is nice because it is (with Adafruit and Sparkfun’s Stemma QT/Qwiik) literally plug and play for beginners, with a wide variety of sensors available. Plus not needing to dedicate a control pin per device added to the bus. Though of course if data throughout is an issue SPI is better than I2C.

If you're going to do I2C just get an LCD display. This OLED can be driven at 150fps by simple devices like an ardunio which is where it really shines - super crisp, high contrast, smoove as buttah graphics for realtime readouts etc. OLED over SPI is really visually impressive stuff and effectively 0 latency. Using the SSD1306 for static displays over I2C is almost a crime.

Re: SSD1306 display drivers and font rendering

#23

Post by bmink »

I’m actually working on code for esp-idf / SSD1309 right now, a little bigger than the 1306. I went through a similar arc as OP.

I was actually surprised / disappointed by the poor quality of the drivers out there. If you instrument and log the bytes u8g2 sends to the device and how the buffer is sent, you see it’s pretty messy, inefficient and hacky. Seems like everyone copy+pasting everyone else’s code, without understanding fully.

So in the end I just decided to draw into a local buffer and then send that buffer in one single transaction to the display.

Once you figure out the data sheet it’s actually very easy to program these displays. For example, to test any SSDxxxx display, you need to send all of two bytes: 0xaf (display on), 0xa5 (all pixels on)

I am now looking at SSD1322, which is both grayscale and has enough internal RAM for two buffers for even smoother drawing (write into a non-displayed region of the RAM and then change the display offset)

Re: SSD1306 display drivers and font rendering

#24

Post by userbinator »

It's worth noting that the controllers for these small displays and their instruction sets have a common lineage that goes back to the 90s --- the SSD1306's looks very much like the Epson S1D15300 series, for example. From a quick search, other controllers with a similar instruction set are ST7565 and UC1601.

Re: SSD1306 display drivers and font rendering

#25

Post by grmnygrmny2 »

bmink wrote: post #23

I’m actually working on code for esp-idf / SSD1309 right now, a little bigger than the 1306. I went through a similar arc as OP. I was actually surprised / disappointed by the poor quality of the drivers out there. If you instrument and log the bytes u8g2 sends to the device and how the buffer is sent, you see it’s pretty messy, inefficient and hacky. Seems like everyone copy+pasting everyone else’s code, without und…

I discovered the same thing with u8g2, and digging through the abstraction layers it felt like improving it was going to be impossible. Sending a single transaction with a framebuffer is so much simpler and faster.

SSD1322 looks great and might be something I look at for the future..

Re: SSD1306 display drivers and font rendering

#26

Post by analog31 »

generj wrote: post #6

This display is the modern 16x2 display for hardware hackers: cheap and versatile. One of my favorite hacks is running this display over HDMI [0]. Note that it’s possible to refresh it at higher rates by using partial refreshes. Or even higher to 150 fps [1]. [0] https://hackaday.com/2022/04/01/making-your-own-technically-... [1] https://hackaday.com/2018/05/08/push-it-to-the-limit-ssd1306...

I switched from 16x2 to SSD1306 because the latter runs on 3.3 V, and is thus more friendly to battery power.

Re: SSD1306 display drivers and font rendering

#29

Post by mianos »

I love this. Once you go to the esp-idf you never want to go back.

I do like lvgl when I get it going, but the way it forces a structure on the code is not to my linking. Every time I start a new project I get annoyed until I get it working.

Re: SSD1306 display drivers and font rendering

#30

Post by hakfoo »

foldr wrote: post #4

It’s generally quite easy to use these over I2C without a driver. You can crib the sequence of initialization commands from the example code supplied by the manufacturer (or loads of examples on GitHub), and then the commands to draw to the screen are pretty straightforward. The chip has its own display RAM, so you don’t need to worry about redrawing every time the display refreshes or anything as low-level as that.

That's what I ended up doing since I was using a CH32V305. It is amusing how many ways you can initialize the display into weird modes like "upside down" or "thinks there's 64 vertical pixels when there's only 32".

I wish they were available in slightly larger models-- even if it's only 128x64, there are plenty of spots where a 5-8cm display would be more legible than the 3cm or less ones that are common,

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