I2C SSD1306 OLED with reset line: Wemos S2 Pico weirdness

[scruss]

SPI OLED screens with a reset line are pretty common, but the MicroPython ssd1306 library doesn't have any way to use them with I2C screens.

The Wemos S2 Pico is an ESP32-S2 board with a 128x32 SSD1306 OLED built in. For the longest time, I couldn't get the display to work. The i2c bus scan would show the right device number, but attempting to display anything created noise:

Looking at the schematic, apart from the nicely-documented pull-up resistors, there's an unexpected RES# line:

It seems you have to set this line high for the display to work at all:

oled_reset = Pin(18, Pin.OUT, value=1)

Seeing an I2C display with a reset line is a first for me. I wouldn't suggest adding support to the library as it can be handled well without changes.

[scruss]

Here's the complete code, including the required reset line activation, to make the OLED on the S2 Pico work:

# for Wemos S2 Pico SSD1306 128x32 display
# https://www.wemos.cc/en/latest/s2/s2_pico.html
# scruss, 2023-02

from machine import Pin, I2C
import ssd1306

# ensure display reset is held high, otherwise nothing will work
oled_reset = Pin(18, Pin.OUT, value=1)
# ESP32 S2 only has one hardware I2C channel, #0 on pins 8 & 9
i2c = I2C(0, sda=Pin(8), scl=Pin(9))
# use default address 0x3C (60) for SSD1306
display = ssd1306.SSD1306_I2C(128, 32, i2c)
display.fill(0)
display.text("* Hello from *", 0, 0, 1)
display.text("*  S2 Pico   *", 0, 8, 1)
display.show()

[dnguyen76]

Do you have a solution for O.66" OLED 64 x 48, it seems don't have reset pin but it doesn't work

[scruss]

It seems to work for me. This for a Lolin S2 mini:

from machine import Pin, I2C, RTC
import s2mini
import ssd1306
import framebuf
import time
WIDTH = 64
HEIGHT = 48
rtc=RTC()

i2c=I2C(0, scl=Pin(s2mini.I2C_SCL), sda=Pin(s2mini.I2C_SDA))
print(i2c.scan())
# should return 49 (0x31 - I2C buttons) and 60 (0x3c - display)
oled = ssd1306.SSD1306_I2C(WIDTH, HEIGHT, i2c)

while True:
    oled.fill(0)
    oled.text("%02d:%02d:%02d" % rtc.datetime()[4:7], 0, 0)
    oled.show()
    time.sleep_ms(200)

[dnguyen76]

My configuration is Wemos D1 mini clone and OLED 64x48 0.66" shield

It seems i get a I2C problem as i2c.scan() function return 112 i2c peripherals from 0x08 to 0x77 ???
(if the oled shield is not connected i2c.scan() return a timeout error)

i2c.readfrom(0x3C, 16) return 0x3C : b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00' (same for 0x3D)
I had found a schematic from LOLIN but my OLED 64x48 shield is a clone
But i don't seen in schematic any information to solve this problem

any idea ?

sch_oled_v2.1.0.pdf

[robert-hh]

It seems that you do not have pull-up resistors on sda and scl

[PBrunot]

It might be necessary to toggle the reset line. On my Lolin S2 Pico the display was still showing noise until I changed your code as follow:

from machine import Pin, I2C
import ssd1306

oled_reset = Pin(18, Pin.OUT)
oled_reset.off()
oled_reset.on()

# ESP32 S2 only has one hardware I2C channel, #0 on pins 8 & 9
i2c = I2C(0, sda=Pin(8), scl=Pin(9))
# use default address 0x3C (60) for SSD1306
display = ssd1306.SSD1306_I2C(128, 32, i2c)
display.fill(0)
display.text("* Hello from *", 0, 0, 1)
display.text("*  S2 Pico   *", 0, 8, 1)
display.show()

[scruss]

The oled_reset = Pin(18, Pin.OUT, value=1) didn't work?

Note: I wasn't really looking for further discussion on this point. This platform doesn't work well for noting observations that don't require further input.

[PBrunot]

I confirm it did not work as it is, toggling the bit was necessary.
I had just flashed the S2 Pico to Micropython 1.20, not sure if it matters.
I replied here because I reached this discussion through Google Search. It came pretty high on "S2 Pico SSD noise issue" (or something like that), so I thought it might be helpful for more people.

[frazzmatazz]

I also confirm it didn't work (just snow/noise) until I used PBrunot's code.

[scruss]

Note: I wasn't really looking for further discussion on this point. This platform doesn't work well for noting observations that don't require further input.