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olikraus / u8g2

U8glib library for monochrome displays, version 2
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USB needed to be connected to run off external power #1129

Closed patchworkalex closed 4 years ago

patchworkalex commented 4 years ago

Running a Teensy4.0 with an SSD1327 128x128 MIDAS display.

The Teensy gets stuck at u8g2.begin() when booting up off external power until a USB device is connected (even a portable USB charger does the trick!). The rest of my code works fine from external power alone when I remove all of the u8g2 functions so I am fairly certain that I've narrowed it down to something in this library, but from scanning though the src files I can't spot anything that would be causing u8g2.begin to become stuck in a loop.

< From reading the PJRC forum it seems in the past people have had issues with void setup waiting for serial commands before continuing. I wonder if that is a helpful clue? >

include "FlexCAN_T4.h"

FlexCAN_T4 <CAN2, RX_SIZE_256, TX_SIZE_16> Can0;

include

include

U8G2_SSD1327_MIDAS_128X128_F_4W_HW_SPI u8g2(U8G2_R2,/ cs=/ 7, /miso dc=/ 9 ) ;

u8g2.begin(); // it gets stuck here!!

olikraus commented 4 years ago

A lib doesn't consume power, but the display does. Begin() will activate the display, which in turn will increase power consumption.

patchworkalex commented 4 years ago

the external power is a l78l05 which can give out up to 100mA. (running from a 3S LiPo)

could this be not enough?

olikraus commented 4 years ago

Depends on your OLED. The 78l05 may also only deliver 100mA with good cooling. Also remember to add at least 1uF caps near the OLED power lines to support the consumption increase.

patchworkalex commented 4 years ago

Sorry for the delayed response, I think you've solved it!

I'm having no problems now that I've increased the power supply

:)