U8G2 does not work on GD32

[flute2k3]

I tried to port the I2C OLED code from STM32duino (which is working) to GD32 but failed, the HW I2C I'm using now with GD32 is SCL(PB8) and SDA(PB9), below is the STM32duino codes associated with OLED:

#include <U8x8lib.h>
U8X8_SSD1306_128X64_NONAME_HW_I2C u8x8(/* reset=*/ U8X8_PIN_NONE);

void setup() {
...
u8x8.begin();
u8x8.setPowerSave(0);
u8x8.setFont(u8x8_font_chroma48medium8_r);
}

void loop() {
...

u8x8.drawString(0,3,"ChipTmp = ");
u8x8.setCursor(10,3);
u8x8.print(In_Temp);

delay(1);
}

the screen is just totally black

[maxgerhardt]

I tested a SSD1306 display with the "Adafruit SSD1306" library and that worked at the time.

Your pins are correct.

ArduinoCore-GD32/variants/GD32F303CC_GENERIC/variant.h

Lines 96 to 97 in a178ad6

	#define PIN_WIRE_SDA PB9
	#define PIN_WIRE_SCL PB8

Can you run the https://playground.arduino.cc/Main/I2cScanner/ sketch to see if it detects an I2C device on the bus at all?

[maxgerhardt]

Hmm actually I just plugged in my SSD1306 and it worked fine with the library.

Using

#include <Arduino.h>
#include <SPI.h>
#include <U8x8lib.h>
U8X8_SSD1306_128X64_NONAME_HW_I2C u8x8(/* reset=*/ U8X8_PIN_NONE);

void setup(void) {
    u8x8.begin();
    u8x8.setPowerSave(0);
    u8x8.setFont(u8x8_font_chroma48medium8_r);
}

void loop(void) {
    u8x8.drawString(0,3,"ChipTmp = ");
    u8x8.setCursor(10,3);
    u8x8.print("Test");
    delay(1000);
}

with platformio.ini

[env]
platform = https://github.com/CommunityGD32Cores/platform-gd32.git
platform_packages = 
    framework-arduinogd32@https://github.com/CommunityGD32Cores/ArduinoCore-GD32.git
monitor_speed = 115200
lib_deps = olikraus/U8g2@^2.34.18

[env:genericGD32F303CC]
board = genericGD32F303CC
framework = arduino

And HW connections between my Bluepill (GD32F303CC chip):

• GND -> GND
• 3.3V -> 3.3V
• PB8 -> SCL
• PB9 -> SDA

The code runs first try.

What's your platformio.ini? Can you reproduce the problem with my minimal sketch above?

[maxgerhardt]

We do seem to have some.. room for improvement though, performance-wise. I've noticed that when you do a display clear and redraw, it's visibly slow. Somewhere it's hitting a timeout in the I2C code. You can lower the default timeout (0xF0000U) a bit when you e.g. set build_flags = -DWIRE_I2C_FLAG_TIMEOUT=0x0F000 in the platformio.ini. But even at base settings, it's working for me.

[flute2k3]

I tried your codes and changed another OLED, same black, hardware connection is the same with only Vcc to 5V (yours 3.3V). BTW, how to upload photo and video?

below is my platformio.ini

; PlatformIO Project Configuration File
;
; Build options: build flags, source filter
; Upload options: custom upload port, speed and extra flags
; Library options: dependencies, extra library storages
; Advanced options: extra scripting
;
; Please visit documentation for the other options and examples
; https://docs.platformio.org/page/projectconf.html

[env:genericGD32F303CC]
platform = gd32
board = genericGD32F303CC
framework = arduino
lib_deps = olikraus/U8g2@^2.34.18

[maxgerhardt]

The SSD1306 OLED with 5V? Doesn't that kill it and would make all the I/O 5V?

[flute2k3]

the spec says Vcc can accept 3.3V to 5V, there is a smt voltage regulator mounted on the board.

[maxgerhardt]

What address does the I2C scanner report? #92 (comment)

[flute2k3]

I got these two line under serial terminal.

I2C Scanner
Scanning...
No I2C devices found

Scanning...
No I2C devices found

Scanning...

[maxgerhardt]

Hm... Does my OLED maybe have 4.7K pullups to VCC on SCL and SDA? I haven't run the address scanner on my board yet, but given that the display reacts for me, I guess it should also be found. "No device" looks like either the device is not responding or there's an electrical problem on the I2C bus or the OLED.

[flute2k3]

no lucky with 4.7k resistor pullup to 5V on both SCL and SDA.

[maxgerhardt]

And when using only 3.3V?