STM32F4 - Vdd @ 3V

Testing/Troubleshooting
1

Hi,

 

I just finished building a CORE_STM32F4 with a MIDI_IO Module. It’s connected with a MB909 MK-IV board but this is another story.

I’ve noticed that 3V output, VDD output are @ 3V… I’d expect 3.3V …

By the way I’m looking into this because I’ve having trouble with the LCD: it’s unstable.

The best way to replicate: hold EDIT button, it makes at lot of message on the SPI, after few seconds the DOGM display becomes full white.

The core is supplied with a 2A PSU. The sofwatre doesn’t crash, can see SPI messages after LCD “crash”.

 

Anyway, the question is:

3V core pin, VDD core pin: are they normal @ 3V or they should be @ 3.3V (at least VDD @3.3V) ?

This document is confusing me:

http://ucapps.de/mbhp_lcd.html

this PDF:

mbhp_lcd_dogm128_mios32.pdf

it talks about the 3.3V but it’s unclear where I can get it on the STM32.

Thanks

 

 

 

 

2

To get some things clear:

  • Do you provide power through USB or J2?
  • What Port are you using to connect the DOGM lcd?

The  MBHP_CORE_STM32 which is mentioned in the pdf is not the same as the  MBHP_CORE_STM32F4 you are using.

3

Afaik, the STM32F4 only has a (very small) 3.0V regulator onboard, that is very easily overloaded, e.g. if you connect more than a few OLEDs or a power-hungry display. You can test that with your fingers on the regulator of the STM32F4 board. If that small regulator gets insanely hot, it is overloaded and that will garble up your display.

A quick solution (that helped me to drive 24 OLEDs) is to install a simple LDO 3.3V voltage regulator and feed its output to the output of the 5V/3.3V selection jumper on the Core.

Many greets, Peter

 

4

Just now, Shuriken said:

To get some things clear:

  • Do you provide power through USB or J2?

J2, with a reulater 5 V 2A psu

  • What Port are you using to connect the DOGM lcd?

I’m using J15A

The  MBHP_CORE_STM32 which is mentioned in the pdf is not the same as the  MBHP_CORE_STM32F4 you are using.

Thanx!  Is out there a connection diagram from the STM32F4 and a DOGM display… I think I’m having issued with the SPI lines … signals are really ugly… LCD a lot of times crashes … 1M resistor (the oscilloscope probe) partially solves the problem and makes the MB909 usable for a longer while

 

5

U1 on the STM32F4 it’s cold… I think it’s the 3V regulator. The LCD + backlight should be less than 40mA.

 

Any hints on the ugly SPI signals ?

6

Not many hints despite maybe a noisy (or underloaded, yes, this happens with some switchers) 5V PSU. Can you 'scope the 5V rail or try another (maybe linear regulated) PSU?

Many greets and good luck!

Peter