crashed when using u8g2 with ssd1306 i2c

[Galen Zhao]

Expected behavior

i2c ssd1306 works well

Actual behavior

device crashed when drawStr called

dofile("oled.lua")
Function platform_gpio_mode() is called. pin_mux:1610614796, func:3
Function platform_gpio_mode() is called. pin_mux:1610614788, func:3
Fatal exception 28(LoadProhibitedCause):
epc1=0x40261e3c, epc2=0x00000000, epc3=0x00000000, excvaddr=0x00000018, depc=0x00000000
�
 ets Jan  8 2013,rst cause:2, boot mode:(3,7)

Test code

Provide a Minimal, Complete, and Verifiable example which will reproduce the problem.

-- display object
local disp

local draw_state, loop_tmr = 0, tmr.create()

-- setup I2c and connect display
local function init_i2c_display()
    -- SDA and SCL can be assigned freely to available GPIOs
    local sda = 5 -- GPIO14
    local scl = 6 -- GPIO12
    local sla = 0x3c
    i2c.setup(0, sda, scl, i2c.SLOW)
    disp = u8g2.ssd1306_i2c_128x64_noname(0, sla)
end

local function u8g2_prepare()
    disp:setFont(u8g2.font_6x10_tf)
    disp:setFontRefHeightExtendedText()
    disp:setDrawColor(1)
    disp:setFontPosTop()
    disp:setFontDirection(0)
  end
  
local function u8g2_ascii_1()
    disp:drawStr( 0, 0, "ASCII page 1")
    for y = 0, 5 do
      for x = 0, 15 do
        disp:drawStr(x*7, y*10+10, string.char(y*16 + x + 32))
      end
    end
  end
  
  local function u8g2_ascii_2()
    disp:drawStr( 0, 0, "ASCII page 2")
    for y = 0, 5 do
      for x = 0, 15 do
        disp:drawStr(x*7, y*10+10, string.char(y*16 + x + 160))
      end
    end
  end
  
init_i2c_display()

disp:clearBuffer()
u8g2_ascii_1()

disp:sendBuffer()

NodeMCU startup banner

NodeMCU 3.0.0.0 built on nodemcu-build.com provided by frightanic.com
branch: release
commit: 4f67927
release: 3.0-release_20201107
release DTS: 202011071523
SSL: false
build type: float
LFS: 0x0 bytes total capacity
modules: adc,ads1115,encoder,enduser_setup,file,gpio,i2c,net,node,pwm,rotary,spi,tmr,u8g2,uart,wifi
build 2020-12-09 14:17 powered by Lua 5.1.4 on SDK 3.0.1-dev(fce080e)

Hardware

nodemcu dev kit,
with ssd1306 i2c oled.
Device found at address 0x3C
Device is wired: SDA to GPIO14 - IO index 5
Device is wired: SCL to GPIO12 - IO index 6

[Galen Zhao]

sorry, forget to call u8g2_prepare()