I2C LCD: code inside

DVE

Hi all,

I'm new on this forum, and with LoPy also.
I want to share my experience with 0.91" 128x32 I2C OLED Display, I forced it to work with LoPy.
Its not mentioned clearly in the manual, i2c pins are G16,G17 on the prototype board (P9-P10 on the LoPy).

So, it works :)
alt text
[0_1479599353875_DSC_0609.JPG]
(It looks like inserting screenshots is not working here btw :) )

Code here: https://github.com/dmitryelj/LoPyI2CLCD

Its only a prototype, will be improved later

PS: Update from 17.12.2016: SPI version added too.

DVE

Strings support added:
alt text

Usage is easy, example:

    import sys,  machine
    
    # Types: 1 - 128x32 I2C OLED Display, 2 - 128x64 I2C OLED Display
    displayType = 1 
    initialize(displayType)
    set_contrast(128) # 1-255
    displayOn()
    clearBuffer()
    addString(0, 0,  sys.platform + " " + sys.version)
    addString(0, 1,  "---")
    addString(0, 2,  "CPU: {} MHz".format(machine.freq()[0]/1000000))
    drawBuffer()

daniel

@DVE Awesome!, thanks for sharing :-)

rskoniec

@DVE Great! What about 128x64 version, because I saw some references in the code? Is it working?

DVE

128x64 display support was added to the source code, but I don't have a real display to test. So, you can try, but no guarantee :)

rskoniec

@DVE OK, thanks. I've just ordered one so I'll have the chance to check and let you know.

brotherdust

@DVE said in I2C LCD: code inside:

Strings support added:
alt text

Usage is easy, example:

    import sys,  machine
    
    initialize()
    set_contrast(128) # 1-255
    displayOn()
    clearBuffer()
    addString(0, 0,  sys.platform + " " + sys.version)
    addString(0, 1,  "---")
    addString(0, 2,  "CPU: {} MHz".format(machine.freq()[0]/1000000))
    drawBuffer()

@DVE Thanks for the code! I ordered a 128x96 display from Adafruit last week and expect to get it on Wednesday. When I have it in-hand, I will test your code and send a pull request over if I can get working. =)

brotherdust

@brotherdust said in I2C LCD: code inside:

@DVE said in I2C LCD: code inside:
Strings support added:

Usage is easy, example:
    import sys,  machine
    
    initialize()
    set_contrast(128) # 1-255
    displayOn()
    clearBuffer()
    addString(0, 0,  sys.platform + " " + sys.version)
    addString(0, 1,  "---")
    addString(0, 2,  "CPU: {} MHz".format(machine.freq()[0]/1000000))
    drawBuffer()
@DVE Thanks for the code! I ordered a 128x96 display from Adafruit last week and expect to get it on Wednesday. When I have it in-hand, I will test your code and send a pull request over if I can get working. =)

ahem Sorry. 128x64.

brotherdust

@DVE So, I tried your code on my 128x64. It just shows up as a bunch of random noise on the display. =( I dug through the MP codebase and found this: https://github.com/pycom/pycom-micropython/blob/master/drivers/display/ssd1306.py

Lo and behold! It's for the same display driver as what we have! Wait.. no framebuf module.

Twiddled with the make configurations and managed to make a build with framebuf included. Trying it now. It's late so I might not report back until tomorrow.

rskoniec

@brotherdust Waiting for the news. :o)

DVE

@brotherdust, thanks for the link. I can test this driver also.

brotherdust

@rskoniec said in I2C LCD: code inside:

@brotherdust Waiting for the news. :o)

Sorry! I was hacking on NyQuil last night. I got the framebuf code to compile and loaded it up on to one of my LoPy's. Tried the driver code, but all I got was the same result: a screen full of static. Same result as when I used @DVE 's code. Maybe my module is defective? Not sure. Anyway, tried a few things, couldn't get it to do anything different, then rage-quit because I wasn't clear-headed enough to figure out what the LoPy was telling me on the console. heh. Either of you have any luck?

brotherdust

Here's what I'm putting in:

# MicroPython SSD1306 OLED driver, I2C and SPI interfaces

from micropython import const
import time
import framebuf


# register definitions
SET_CONTRAST        = const(0x81)
SET_ENTIRE_ON       = const(0xa4)
SET_NORM_INV        = const(0xa6)
SET_DISP            = const(0xae)
SET_MEM_ADDR        = const(0x20)
SET_COL_ADDR        = const(0x21)
SET_PAGE_ADDR       = const(0x22)
SET_DISP_START_LINE = const(0x40)
SET_SEG_REMAP       = const(0xa0)
SET_MUX_RATIO       = const(0xa8)
SET_COM_OUT_DIR     = const(0xc0)
SET_DISP_OFFSET     = const(0xd3)
SET_COM_PIN_CFG     = const(0xda)
SET_DISP_CLK_DIV    = const(0xd5)
SET_PRECHARGE       = const(0xd9)
SET_VCOM_DESEL      = const(0xdb)
SET_CHARGE_PUMP     = const(0x8d)


class SSD1306:
    def __init__(self, width, height, external_vcc):
        self.width = width
        self.height = height
        self.external_vcc = external_vcc
        self.pages = self.height // 8
        self.buffer = bytearray(self.pages * self.width)
        self.framebuf = framebuf.FrameBuffer1(self.buffer, self.width, self.height)
        self.poweron()
        self.init_display()

    def init_display(self):
        for cmd in (
            SET_DISP | 0x00, # off
            # address setting
            SET_MEM_ADDR, 0x00, # horizontal
            # resolution and layout
            SET_DISP_START_LINE | 0x00,
            SET_SEG_REMAP | 0x01, # column addr 127 mapped to SEG0
            SET_MUX_RATIO, self.height - 1,
            SET_COM_OUT_DIR | 0x08, # scan from COM[N] to COM0
            SET_DISP_OFFSET, 0x00,
            SET_COM_PIN_CFG, 0x02 if self.height == 32 else 0x12,
            # timing and driving scheme
            SET_DISP_CLK_DIV, 0x80,
            SET_PRECHARGE, 0x22 if self.external_vcc else 0xf1,
            SET_VCOM_DESEL, 0x30, # 0.83*Vcc
            # display
            SET_CONTRAST, 0xff, # maximum
            SET_ENTIRE_ON, # output follows RAM contents
            SET_NORM_INV, # not inverted
            # charge pump
            SET_CHARGE_PUMP, 0x10 if self.external_vcc else 0x14,
            SET_DISP | 0x01): # on
            self.write_cmd(cmd)
        self.fill(0)
        self.show()

    def poweroff(self):
        self.write_cmd(SET_DISP | 0x00)

    def contrast(self, contrast):
        self.write_cmd(SET_CONTRAST)
        self.write_cmd(contrast)

    def invert(self, invert):
        self.write_cmd(SET_NORM_INV | (invert & 1))

    def show(self):
        x0 = 0
        x1 = self.width - 1
        if self.width == 64:
            # displays with width of 64 pixels are shifted by 32
            x0 += 32
            x1 += 32
        self.write_cmd(SET_COL_ADDR)
        self.write_cmd(x0)
        self.write_cmd(x1)
        self.write_cmd(SET_PAGE_ADDR)
        self.write_cmd(0)
        self.write_cmd(self.pages - 1)
        self.write_data(self.buffer)

    def fill(self, col):
        self.framebuf.fill(col)

    def pixel(self, x, y, col):
        self.framebuf.pixel(x, y, col)

    def scroll(self, dx, dy):
        self.framebuf.scroll(dx, dy)

    def text(self, string, x, y, col=1):
        self.framebuf.text(string, x, y, col)


class SSD1306_I2C(SSD1306):
    def __init__(self, width, height, i2c, addr=0x3c, external_vcc=False):
        self.i2c = i2c
        self.addr = addr
        self.temp = bytearray(2)
        super().__init__(width, height, external_vcc)

    def write_cmd(self, cmd):
        self.temp[0] = 0x80 # Co=1, D/C#=0
        self.temp[1] = cmd
        self.i2c.writeto(self.addr, self.temp)

    def write_data(self, buf):
        self.temp[0] = self.addr << 1
        self.temp[1] = 0x40 # Co=0, D/C#=1
        self.i2c.start()
        self.i2c.write(self.temp)
        self.i2c.write(buf)
        self.i2c.stop()

    def poweron(self):
        pass

from machine import I2C
i2c = I2C(0, I2C.MASTER, baudrate=1000000)
display = SSD1306_I2C(width=128, height=64, i2c=i2c, addr=0x3d)

The 128x64 display has hardware address of 0x3d. Anyway, here's what comes out:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 109, in __init__
  File "<stdin>", line 37, in __init__
  File "<stdin>", line 64, in init_display
  File "<stdin>", line 89, in show
  File "<stdin>", line 119, in write_data
AttributeError: 'I2C' object has no attribute 'start'

The display turns on, but it's full of what looks like random noise. I looked through the source code for the I2C module and the start method is there:
https://github.com/pycom/pycom-micropython/blob/master/esp32/mods/machine_i2c.c#L348

STATIC mp_obj_t machine_i2c_start(mp_obj_t self_in) {
    machine_i2c_obj_t *self = MP_OBJ_TO_PTR(self_in);
    mp_hal_i2c_start(self);
    return mp_const_none;
}
MP_DEFINE_CONST_FUN_OBJ_1(machine_i2c_start_obj, machine_i2c_start);

>>> help(machine.I2C)
<class 'I2C'>object  is of type type
  init -- <function>
  scan -- <function>
  readfrom -- <function>
  readfrom_into -- <function>
  writeto -- <function>
  readfrom_mem -- <function>
  readfrom_mem_into -- <function>
  writeto_mem -- <function>
  MASTER -- 0

I don't get why it's not present in the list of available methods for this class. =/

brotherdust

@DVE Update on using the built-in framebuffer and SSD1306 driver:
The driver was using I2C "primitives" that were disabled in the esp32 version of machine_i2c. The recent commits I've made on my relevant github repo:
https://github.com/brotherdust/pycom-micropython/commits/i2c-framebuf

I've made progress; but still learning how to use this stuff!

brotherdust

It works! Yay! Code later. Sleep now.

DVE

@brotherdust Its great :)

I ordered 128x64 display too on Ebay, will be able to test next week.

@brotherdust said in I2C LCD: code inside:

The driver was using I2C "primitives" that were disabled in the esp32 version of machine_i2c

How it works? Do you need to reload a firmware with enabled primitives?

rskoniec

@brotherdust Any chance for a code and answers for @DVE questions?

brotherdust

@rskoniec said in I2C LCD: code inside:

@brotherdust Any chance for a code and answers for @DVE questions?

@rskoniec, my apologies. I thought that I had answered this and didn't give it any more thought.

The commit I referenced enables the I2C primitives. You'll need to recompile the firmware and upload it. Then the code will work.

After reviewing the code a bit more, I think it can be refactored not to use the primitives (I2C.start, stop, etc). The primitives are already a part of other, more high-level routines. But the easiest way to get the driver going was just to enable those functions. =) I'm too lazy to re-factor and go through all the pull requests and justifications to get it included upstream.

rskoniec

@brotherdust Thank you very much for quick reply. :o)

DVE

Got the 128x64 display this week. Stupid chinese seller sent SPI version instead of I2C.
But I was able to add SPI support as well :)
alt text

Will update code soon.

Explore Pybytes | Official Documentation | Report a Firmware Bug/Issue | GitHub

I2C LCD: code inside

Pycom on Twitter