Seetron GLO-216 screen with Spark

Hi everyone,
I’ve been struggling on try to get Seetron GLO-216 screen working with Spark for a while now and wondering if there is any suggestion. The screen operate on both 5 and 3.3 v and works really well with my Arduino Mega via SoftSerial. However, when I tried to do it directly from TX from Spark via Serial1, it doesn’t work…

Here is my code:
(Derived from

//this portion came from GLO-216 arduino libs

// Moves printing position to the first character of top line
char homeCursor() {  return 0x01;}
// Cycles the font size: normal -> tall -> wide -> big -> normal -> ...
char selectSize() {  return 0x02;}
// Sets font size to default of small on two lines of 16 characters
char defaultSize() {  return 0x03;}
// Behaves like the backspace key
char backspace() {  return 0x08;}
// Moves printing position to the next multiple of 4 location
char tab() {  return 0x09;}
// Moves the printing position down a line
char linefeed() {  return 0x0A;}
// Moves the printing position up a line
char verticalTab() {  return 0x0B;}
// Clears the screen and moves printing position to 0
char clearScreen() {  return 0x0C;}
// Moves to the first printing position of the next line
char carriageReturn() {  return 0x0D;}
// Turns on the OLED driver circuitry when it has been previously turned off
char turnOn() {  return 0x0E;}
// Turns off the OLED driver circuitry to save power
char turnOff() {  return 0x0F;}
// Sets the printing position according to value of next byte
char setPosition() {  return 0x10;}
// Prints text at the righthand end of a field of defined size from 2-8
char rightAlign() {  return 0x12;}
// Sets seven segment style font for large characters
char sevenSeg() {  return 0x13;}
// Sets text style font for large characters
char textStyle() {  return 0x14;}
// Begin multi-part instruction
char escape() {  return 0x1B;}
// See
char bpkInstr() {  return 0xFE;}

int inverted = 1;

void setup() {

void loop() {

// clears the screen and select font size and style
  char instr1[] = {
    selectSize(), // tall
    selectSize(), // wide
    selectSize(), // big
  const char message[] = "Hi GLO!";
  // print message according to prior instructions

Any idea what’s going on?
Appreciated, Thanks!

I think I’ve already found the root of all evil myself while I forming that question.
GLO-216 is communicated through inverted Serial by default, cutting the Spol jumper does the trick. Now we’re talking.

What our stories teach us: Read the docs. carefully :wink:

firmread, your loop has no delays so the display will clear/write VERY fast and will most likely overwhelm the display. If you add a delay(2000) at the end of loop() does it work?

Well, I’m glad you found that little surprise and fixed it. Good job! :smile:

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