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MIDI Test Code on Arduino and STM32 Blue Pill

This code turns the onboard PC13 LED of the STM32 Blue Pill on when a MIDI NoteOn message is received and turns the LED off when a MIDI Noteoff message is received. It’s my preferred way to confirm that a MIDI circuit is working. It relies on the Arduino MIDI Library.

#include <MIDI.h>

#define LED PC13 // LED pin on Arduino Uno


void doSomeStuffWithNoteOn(byte channel, byte pitch, byte velocity);
void NoteOff(byte channel, byte note, byte velocity);

void setup()
  pinMode(LED, OUTPUT);

void loop()

void doSomeStuffWithNoteOn(byte channel, byte pitch, byte velocity)
  // note on code goes here
  digitalWrite(PC13, LOW);

void NoteOff(byte channel, byte note, byte velocity)
  // note off code goes here
  digitalWrite(PC13, HIGH);
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Heating Bed and Nozzle Simultaneously On CR-10 In Cura

On my CR-10, the nozzle heats up and then the bed heats up. This seems like a waste of time particularly in that I need to make sure the first layer of the print goes down correctly. After that, I don’t care. This sequentially heating dramatically increases my time investment in a print.

Warning: I’ve heard that the stock CR-10 power supply is trash and can’t handle this. I’ve been doing it for about a year (hundreds of prints) with no issue. Use at your own risk.

In Cura, go to Settings > Printer > Manage Printer > Machine Settings > Printer


M140 S{material_bed_temperature} ; start preheating the bed WITHOUT wait to what is set in Cura

M104 S{material_print_temperature} T0 ; start preheating hotend WITHOUT wait to what is set in Cura

M190 S{material_bed_temperature} ; start heating the bed to what is set in Cura and WAIT

M109 S{material_print_temperature} T0 ; start heating hotend to what is set in Cura and WAIT

M201 X500.00 Y500.00 Z100.00 E5000.00 ;Setup machine max acceleration

M203 X500.00 Y500.00 Z10.00 E50.00 ;Setup machine max feedrate

M204 P500.00 R1000.00 T500.00 ;Setup Print/Retract/Travel acceleration

M205 X8.00 Y8.00 Z0.40 E5.00 ;Setup Jerk

M220 S100 ;Reset Feedrate

M221 S100 ;Reset Flowrate

G28 ;Home

G92 E0 ;Reset Extruder

M92 E98 ; Brando configured extruder e-steps

G1 Z2.0 F3000 ;Move Z Axis up

G1 X10.1 Y20 Z0.28 F5000.0 ;Move to start position

G1 X10.1 Y200.0 Z0.28 F1500.0 E15 ;Draw the first line

G1 X10.4 Y200.0 Z0.28 F5000.0 ;Move to side a little

G1 X10.4 Y20 Z0.28 F1500.0 E30 ;Draw the second line

G92 E0 ;Reset Extruder

G1 Z2.0 F3000 ;Move Z Axis up

——— END G-CODE ————————–

G91 ;Relative positionning

G1 E-2 F2700 ;Retract a bit

G1 E-2 Z0.2 F2400 ;Retract and raise Z

G1 X5 Y5 F3000 ;Wipe out

G1 Z10 ;Raise Z more

G90 ;Absolute positionning

G1 X0 Y{machine_depth} ;Present print

M106 S0 ;Turn-off fan

M104 S0 ;Turn-off hotend

M140 S0 ;Turn-off bed

M84 X Y E ;Disable all steppers but Z

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Blue Pill STM32 Clones Brown Out or Become Unresponsive

The Problem:  The STM32 Blue Pill sometimes dies for no apparent reason.  On the PSU, it’s pulling 30mA and then for now apparent reason, the current draw reduces to 10mA (for the power indicator LED, presumably) and the microcontroller appears dead.  It only seems to occur when powered from a power supply to the 5V pin.   Once it occurs, giving the 3.3V pin power instead appears to do no good.

For some reason, I’ve been able to fix the problem reliability by removing external power and powering the STM32 via the Stlink clone along with the CLK, GND, and IO pins.  Voltage SHOULD be voltage in such a situation, but maybe the IO pin has some kind of effect.  I’m really not sure.  If anyone knows, please pass on why.

I’ve wondered if the problem is some kind of BOR brownout problem, but I haven’t done the work to find out yet.  It only seems to happen with the CS32F103C8T6 STM32 Blue Pill clones (which I currently have 9 of I need to burn through and never buy again.)