STM32+epaper, weird signal

[Moriambar]

Hi there,
around 4 years ago I started experimenting with the bluepill and some 4.2 inch epaper displays. Everything was fine and dandy so I decided to design my own circuit.
Well long story short I postponed the project up until today, I soldered my stuff, programmed the stm32 and connected the module.
Result: nothing.
I probed the board and either with the module connected or disconnected both busy and rst lines were ~1V, which I think is kinda low.
The project is powered by 3.3V via linear psu.
What am I doing wrong?
Here's the code (I use the arduino ide)

Code: [Select]

#include <GxEPD2_BW.h> // including both doesn't use more code or ram
#include <GxEPD2_3C.h> // including both doesn't use more code or ram
#include <Fonts/FreeMonoBold24pt7b.h>
#include <Fonts/FreeMonoBold18pt7b.h>
#include <Fonts/FreeMonoBold12pt7b.h>

// select the display class and display driver class in the following file (new style):
#include "GxEPD2_display_selection_new_style.h"
void setup()
{
  display.init();
  // comment out next line to have no or minimal Adafruit_GFX code
  display.setTextColor(GxEPD_BLACK);
 
  display.firstPage();
 
  do
  {
    display.fillScreen(GxEPD_WHITE);
    display.println();
    display.println();
 
    display.setFont(&FreeMonoBold18pt7b);
   
    // comment out next line to have no or minimal Adafruit_GFX code
  display.print("   CIAO");
  display.println("Oggi e` il 18"); 
    //display.print("Hello World!");
  }
  while (display.nextPage());
 
}

void loop() {};
this gets uploaded fine.
Attached the schematic for my project. Currently only the RTCC and the stm32 are installed, but I'm not using them (see code), since I wanted just to see whether the display worked.
Thanks for any help.

[temperance]

I probed the board and either with the module connected or disconnected both busy and rst lines were ~1V, which I think is kinda low.

How did you probe the board? With an oscilloscope?

[Moriambar]

I probed the board and either with the module connected or disconnected both busy and rst lines were ~1V, which I think is kinda low.

How did you probe the board? With an oscilloscope?

yes, sorry for not having specified it before. the ground lead was on the" -"input fromthe PSU

[temperance]

Looking at the display data sheet: busy is, as expected, an output and RST is an input.

The busy line and the SPI interface will not do anything as long as the RST line is not properly driven. I would would start by investigating if the output to drive the RTS line is configured as an output an set to the correct level. But that will probably be difficult to probe because RST is probably driven only 1 time when the code starts. Debugging such things is easier if you change the software a bit to toggle the line contentiously.

[Moriambar]

sorry guys.
As usual the problem was between the chair and the keyboard. I uploaded the wrong sketch. Now all is fine and dandy