ESP32 Forum

Posted: **Sat Apr 01, 2023 2:37 pm**

Hi!

I recently ordered an esp32-c3-01m kit microcontroller and encountered two issues with it.

I would like to use it to drive a 7-segment display, but I noticed that the display flashes approximately every 2 seconds (there is no delay or serial print in the code). I won't include the code for this because it also causes the LEDs on the board (cold and warm white) to flash simultaneously after a simple digitalWrite turn-on.

The other problem is with the serial monitor.
Previously, with the esp32, I was used to sending debug messages to the serial monitor when it started/restarted, but this does not send anything. Even with the following basic code, I don't get anything when I open the serial monitor:

Code: [Select all] [Expand/Collapse]

void setup() {
  Serial.begin(115200);
  pinMode(18, OUTPUT); //Cold and warm white built in led
  pinMode(19, OUTPUT);
}
 
void loop() {
  digitalWrite(18, HIGH);
  digitalWrite(19, HIGH);
  Serial.println("hello");
  delay(1000);
}

GeSHi © Codebox Plus Extension

The only thing I notice when I open the serial monitor is that all the LEDs on the board turn off, and they turn on again when I close the serial monitor.
For me, Serial is not important for this project, but I thought maybe it's related to the two issues. If the LEDs wouldn't flash, I would be satisfied with it.
Does anyone have any ideas or has anyone experienced something similar?

Posted: **Sun Apr 02, 2023 1:13 am**

If you're using the built-in USB-serial converter, your use of GPIO18/19 is the issue; these normally are the pins USB is connected to and reconfiguring them will break that connection.

Posted: **Sun Apr 02, 2023 10:01 am**

Thanks for the quick reply. There is a ch340c ic on the board that does the serial-usb conversion. I tried the code pins 18 and 19 excluded, but the same issue.

Posted: **Mon Apr 03, 2023 12:34 am**

How did you connect the 7-segment display? Are you sure you're not hooking anything up to the ESP TxD0/RxD0 pins?

Posted: **Mon Apr 03, 2023 8:05 am**

Code: [Select all] [Expand/Collapse]

#include "SevSeg.h"
SevSeg sevseg;
 
const int dig1 = 9;  
const int dig2 = 8;  
const int dig3 = 1;  
const int dig4 = 0;   
const int A = 6;   
const int B = 10;      
const int C = 5;    
const int D = 4;     
const int E = 3;     
const int F = 2;      
const int G = 7;       
 
int sec = 0;
unsigned long preTime = 0;
 
 
void setup() {
  byte numDigits = 4;
  byte digitPins[] = {dig1, dig2, dig3, dig4};
  byte segmentPins[] = {A, B, C, D, E, F, G, -1};
  bool resistorsOnSegments = false; // 'false' means resistors are on digit pins
  byte hardwareConfig = COMMON_ANODE; // See README.md for options
  bool updateWithDelays = false; // Default 'false' is Recommended
  bool leadingZeros = false; // Use 'true' if you'd like to keep the leading zeros
  bool disableDecPoint = true; // Use 'true' if your decimal point doesn't exist or isn't connected
  sevseg.begin(hardwareConfig, numDigits, digitPins, segmentPins, resistorsOnSegments,
               updateWithDelays, leadingZeros, disableDecPoint);
  sevseg.setBrightness(100);
}
 
void loop()
{
  sevseg.refreshDisplay();
  if (millis() - preTime > 1000)
  {
    sevseg.setNumber(sec);
    if (sec != 100) sec++; //count to 100 and stop
    preTime = millis();
  }
}

At this code, I stop the counting at 100, and it is clearly visible that the 7-segment display flashes approximately every 2 seconds (which is obviously not caused by the display refreshing since the content is static). I apologize if I worded it ambiguously. I don't intend to use serial communication in the project, I just mentioned it because it doesn't work, and I thought it might be related to the display flashing. The flashing of the display is my main issue.

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