I'm not understanding what's going on with my Uno. I have a very simple piece of code. no peripherals are connected. Just a bare genuine uno. I program in VisualMicro for Visual Studio.

void setup()

    char stringy[9] = { 0x7E, 0x00, 0x05, 0x08, 0x01, 0x44, 0x33, 0x04, 0x7B };

    for (int i = 0; i < 9; i++) {



void loop()
    while (1) {  }

Without a delay of around 250msec or greater in the for loop, I don't get all the characters. In fact, without the delay, the code doesn't even finish executing. I only get the first character '~'. It doesn't seem to matter what my baud rate is.

This code runs fine without a delay on my Nano. What could possibly be the issue?

  • Your program works as expected on my Uno. – Edgar Bonet Sep 15 '17 at 20:51
  • Weird. You get the whole array of gibberish in your serial pane? I'm starting to think its just a difference in compilers. – LegitimateWorkUser Sep 15 '17 at 20:55
  • Not the serial pane (I'm not using the IDE). I typed stty -F /dev/ttyACM0 raw 115200 && hd -n 15 /dev/ttyACM0 on the Linux console and got 00000000 7e 00 05 08 01 44 33 04 7b 0d 0a 64 6f 6e 65 |~....D3.{..done| (hd is a hexdump utility). – Edgar Bonet Sep 15 '17 at 21:06

You are printing the unprintable.

Do you think it should print:



0x7E 0x00 0x05 0x08 0x01 0x44 0x33 0x04 0x7B 

What you will get is

start of heading
end of transmission
open brace

I think you can call

Serial.print(stringy[i], HEX);

To see the number you put in come out.

| improve this answer | |
  • I expect it to come out gibberish, like this: ~ D3 { (three of those white spaces actually show as strange characters that I can't paste here.) The actual content of the array is an Xbee AT command, and I designed this as an experiment to see why it's not working. See, when I use the Xbee library with the nano and monitor the serial output without the xbee connected, ~ D3 { is what I see. But on the Uno, all I get out is ~. In this experiment I was trying to replicate the output with serial.print(), and the result is the same. – LegitimateWorkUser Sep 15 '17 at 16:29

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