pins/i2c and embedded:io/I2C cannot be used on the same bus?

[tve]

I have an ssd1306 display and some other devices on an i2c bus on an esp32-c3. The devices use embedded:io/I2C and as soon as I add "screen": "ssd1306" to the manifest the other devices cease to work. It looks like pins/i2c (used by the sssd1306 driver) and embedded:io/i2c can't be used on the same bus? Is there an embedded:io driver for the ssd1306? Or am I seeing phantoms?

[tve]

@phoddie would you mind giving me a quick opinion on the above question? As it stands I'm probably going to port the ssd1306 driver to embedded:io/i2c this week-end but I'd really prefer not to have to do that...

[phoddie]

Apologies. I overlooked this.

You are correct - the two I2C implementations aren't intended to be used together. I took another look at supporting that, but it is a fair amount of work. I'd rather put that time into migrating forward to the ECMA-419 APIs.

The SSD1306 is pretty simple. We actually have a basic pure JavaScript driver that works with an early draft of ECMA-419. It should be straightforward to get working with the latest. The pixel swizzling would be faster in C, but that's just an optimization. It could/should probably be updated to support dithering using the techniques of the gdew0154m09 driver (used for M5Core Ink). I can post that driver later, if it would help.

[tve]

yes, if you can post the driver that would be awesome! Thanks for the reply!

[phoddie]

Here you go.

ssd1306.js

import I2C from "builtin/i2c";
import Bitmap from "commodetto/Bitmap";

const HEIGHT = 64;
const WIDTH = 128;

const SSD1306_SETCONTRAST =  0x81
const SSD1306_DISPLAYALLON_RESUME =  0xA4
const SSD1306_NORMALDISPLAY =  0xA6
const SSD1306_DISPLAYOFF =  0xAE
const SSD1306_DISPLAYON =  0xAF
const SSD1306_SETDISPLAYOFFSET =  0xD3
const SSD1306_SETCOMPINS =  0xDA
const SSD1306_SETVCOMDETECT =  0xDB
const SSD1306_SETDISPLAYCLOCKDIV =  0xD5
const SSD1306_SETPRECHARGE =  0xD9
const SSD1306_SETMULTIPLEX =  0xA8
const SSD1306_SETSTARTLINE =  0x40
const SSD1306_MEMORYMODE =  0x20
const SSD1306_COLUMNADDR =  0x21
const SSD1306_PAGEADDR   =  0x22
const SSD1306_COMSCANDEC =  0xC8
const SSD1306_SEGREMAP =  0xA0
const SSD1306_CHARGEPUMP =  0x8D
const SSD1306_EXTERNALVCC =  0x1
const SSD1306_SWITCHCAPVCC =  0x2
const SSD1306_DEACTIVATE_SCROLL =  0x2E
const vccstate = SSD1306_SWITCHCAPVCC

const kBufferSlop = 1;

function doCmd(ssd, cmd) {
	ssd.write(new Uint8Array([0, cmd]).buffer);
}

export default class SSD1306 {
	constructor() {
		let ssd = this.ssd1306 = new I2C({
			sda: 5,
			scl: 4,
			hz: 1000000,
			address: 0x3C,
		});

		doCmd(ssd, SSD1306_DISPLAYOFF);                    // 0xAE
		doCmd(ssd, SSD1306_SETDISPLAYCLOCKDIV);            // 0xD5
		doCmd(ssd, 0x80);                                  // the suggested ratio 0x80

		doCmd(ssd, SSD1306_SETMULTIPLEX);                  // 0xA8
		doCmd(ssd, HEIGHT-1);

		doCmd(ssd, SSD1306_SETDISPLAYOFFSET);              // 0xD3
		doCmd(ssd, 0x0);                                   // no offset
		doCmd(ssd, SSD1306_SETSTARTLINE | 0x0);            // line #0
		doCmd(ssd, SSD1306_CHARGEPUMP);                    // 0x8D
		if (vccstate == SSD1306_EXTERNALVCC)
		{ doCmd(ssd, 0x10); }
		else
		{ doCmd(ssd, 0x14); }
		doCmd(ssd, SSD1306_MEMORYMODE);                    // 0x20
		doCmd(ssd, 0x00);                                  // 0x0 act like ks0108
		doCmd(ssd, SSD1306_SEGREMAP | 0x1);
		doCmd(ssd, SSD1306_COMSCANDEC);

		if ((128 == WIDTH) && (64 == HEIGHT)) {
			doCmd(ssd, SSD1306_SETCOMPINS);                    // 0xDA
			doCmd(ssd, 0x12);
			doCmd(ssd, SSD1306_SETCONTRAST);                   // 0x81
			doCmd(ssd, 0xCF);
		} else {
			throw Error("height/width not supported");
			return;
		}

		doCmd(ssd, SSD1306_SETPRECHARGE);                  // 0xd9
		if (vccstate == SSD1306_EXTERNALVCC)
		{ doCmd(ssd, 0x22); }
		else
		{ doCmd(ssd, 0xF1); }
		doCmd(ssd, SSD1306_SETVCOMDETECT);                 // 0xDB
		doCmd(ssd, 0x40);
		doCmd(ssd, SSD1306_DISPLAYALLON_RESUME);           // 0xA4
		doCmd(ssd, SSD1306_NORMALDISPLAY);                 // 0xA6

		doCmd(ssd, SSD1306_DEACTIVATE_SCROLL);

		doCmd(ssd, SSD1306_DISPLAYON);						//--turn on oled panel
	}
	begin(x, y, width, height) {
		if ((0 != x) || (0 != y) || (WIDTH != width) || (HEIGHT != height)) {
			trace("partial updates unsupported\n");
			return;
		} else {
			let ssd = this.ssd1306;

			doCmd(ssd, SSD1306_COLUMNADDR);
			doCmd(ssd, 0);   // Column start address (0 = reset)
			doCmd(ssd, WIDTH-1); // Column end address (127 = reset)

			doCmd(ssd, SSD1306_PAGEADDR);
			doCmd(ssd, 0); // Page start address (0 = reset)

			doCmd(ssd, (HEIGHT >> 3) - 1);	// Page end address

			this.pixel = 1;
			this.out = new Uint8Array(WIDTH+kBufferSlop);
			this.out[kBufferSlop - 1] = 0x40;
			this.out.fill(0, kBufferSlop);
		}
	}
	send(data, offset, count) {
		if (undefined !== offset && offset > 0) {
			data = data.slice(offset);
			if (undefined === count) count = pixels.length;
			else count -= offset;
		} else {
			offset = 0;
			count = data.byteLength;
		}
		let pixels = new Uint8Array(data);

		let ssd = this.ssd1306;
		if (count < 0) count = -count;
		let pixel = this.pixel

		let out = this.out;
		while (count) {
			let i = WIDTH - 1;
			while (i--) {
				if (pixels[i] & 128)
					out[kBufferSlop+i] |= pixel;
			}

			pixel <<= 1;
			if (256 === pixel)	 {	// flush this set of 8 lines
				ssd.write(out.buffer)
				// start new group of 8 rows
				out.fill(0, kBufferSlop);
				pixel = 1;
			}

			count -= WIDTH;
		}
		this.pixel = pixel;
	}
	end() {}
	continue() {}
	pixelsToBytes(count) {
		return count;
	}
	get pixelFormat() {
		return Bitmap.Gray256;
	}
	get width() { 
		return WIDTH; 
	}
	get height() {
		return HEIGHT;
	}
	get c_dispatch() {
		return undefined;
	}
	adaptInvalid(r) {
		r.x = 0;
		r.y = 0;
		r.w = this.width;
		r.h = this.height;
	}
}

This was written before the host instance provider was added, so it imports I2C directly (using a now stale module specifier). That should be easy to change. Beyond that, it should be pretty close. Good luck!

[tve]

Quick FYI:

• pixels is undefined on the 3rd line of send() (it looks like it's an unused code path)
• the loop in send keeps sending the first scanline: the pixels[i] & 128 test needs a line offset, e.g., pixels[off+i]
• the loop also doesn't render the last row: i needs to be initialized to WIDTH, not WIDTH-1

Is there a way I can see the bytecode generated so I can see whether I can optimize the inner loop?

[tve]

I took the driver posted by @phoddie, fixed the issues mentioned in my previous comment, and added typescript types, plus an example. It's now pushed to my repo: https://github.com/tve/modtve/tree/main/modules/drivers/displays/ssd1306-io
I hope this helps the next person...
(I only tested on a 128x32 display, so there could be issues on other dimensions)