Serial print oddity

Using Arduino Programming Questions
1

Have noticed gobbledegook being printed at beginning of first line of print... simple example shown below.......

void setup() {
  Serial.begin(9600);
  char sdata[] = "asdfghjkl";
  int ax = 20;
  int ay = 40;
  prtout(sdata,ax,ay);
}
void loop() {
}
void prtout(char *data, int px, int py){
  Serial.println();
  Serial.println(px);
  Serial.println(py);
  Serial.write(data,strlen(data));
}

....which results in....

20:14:41.658 -> ! Pt0bcbbb %q  ) !@:
20:14:41.819 -> 20
20:14:41.819 -> 40
20:14:41.819 -> asdfghjkl

The Serial monitor is set to 9600.

Any answers?

2

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3

Your code works OK for me. It prints what I would expect

Which Arduino board are you using ?
What prints if you reset the board after uploading the code ?

4

Try adding delay(500) after Serial.begin(9600). On some boards you need to allow some time for USBSerial to get connected.

5

Using an ESP-WROOM-32 board

6

I tried delay(500) an delay(1000); but still see the junk.
What I do notice is that the junk prints followed by a delay then followed by the real data.
Seems to suggest something to do with the begin() statement.

7

I suspect that what you are seeing is the standard output from the ESP32 that occurs when it is booted up but it is not output at 9600 baud

If you set the baud rate of the sketch and Serial monitor to 115200 it will probably look something like this if you reset the board after uploading the code

ets Jun  8 2016 00:22:57

rst:0x1 (POWERON_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
configsip: 0, SPIWP:0xee
clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
mode:DIO, clock div:1
load:0x3fff0030,len:1344
load:0x40078000,len:13964
load:0x40080400,len:3600
entry 0x400805f0

20
40
asdfghjkl
8

Definitely something to do with the Begin() statement. I put in a 5 sec delay - junk printed immediately, followed by 5 sec wait then real data printed. Odd.

9

Yes, exactly right. I didn't know that the ESP standard was 115200.
Thanks for your help.

10

Problem solved - UKHeliBob answered, all to do with Serial output rate, should be 115200 on ESP32.... I was using 9600.
Thanks for your reply.

11

For my part I use 115200 on all Arduinos

12

That's the baud rate from the 80's. I don't know why it's in every Arduino example like that.

13

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