Im trying to use an OLED display (uOLED-96-G1 http://www.sparkfun.com/products/8538) with an Arduino Mega 2560. The display has a serial interface, and should be able to automatically detect the baud rate.
I have connected:
Display Power → Arduino +5V
Display Ground → Arduino Ground
Display Reset → Arduino Digital Pin 8
Display RX → 100 Ohm resistor → Arduino TX
Display TX → Arduino RX
Nothing else is connected to the Arduino. The Display does not have an SDCard inserted, and there is a “Run” jumper that is not documented in the display’s specifications, but I have tested it with the jumper on and without it.
According to the documentation, the display controller is supposed to be able to automatically detect the serial baud rate. This is done by sending the byte 0x55. The display is then supposed to return an ACK of 0x06 or a failure of 0X15.
When the Arduino starts up, the display turns on. It displays some hardware information about the display itself (the component name and firmware version) for a period of time ranging from 10 seconds to 30 seconds. The display then goes dark and will not come on again until either the Arduino is restarted, or the reset pin is switched from high to low, and then to high again.
In either case, when I try to issue the baud rate detection byte 0x55, the display never responds. The call to read the ACK/NAK byte from the display just blocks forever. I have tried adding delays between various different steps in the process and have still not been able to get past waiting for the response byte.
I’m new to Arduinos, so I’m wondering if there’s something obvious I’m missing here in regards to correct serial communication techniques. For all I know, the 0x55 byte isn’t even making it to the display, so the problem could be either that the Arduino’s transmissions aren’t making it to the display, or the displays transmissions aren’t making it back to the Arduino. I don’t really know how I could test to see which is the case.
I have tested the serial communication to the Arudino serial monitor and that does work. But that doesn’t really tell me much.
The following is a simple sketch I’m trying to get working. Its supposed to just turn on the display and set a pixel at (10, 10) to white.
const long OLED_BAUD_RATE = 57600;
const int OLED_RESET_PIN = 8;
/**
* Startup routine
*/
void setup(){
// Start the log monitor serial port
Serial.begin(9600);
// Setup the restart pin for the display
pinMode(OLED_RESET_PIN, OUTPUT);
// Sleep for 10 seconds
for (int x = 0; x < 10; x++) {
delay(1000);
Serial.print("Sleeping ");
Serial.print(x, DEC);
Serial.println("");
}
// Restart the display
displayRestart();
delay(4000);
// Initialize the display
displayInit();
delay(4000);
}
/**
* Restart the OLED display by lowering and raising the reset pin
*/
void displayRestart() {
Serial.println("Restarting the display");
delay(10);
digitalWrite(OLED_RESET_PIN,LOW);
delay(10);
digitalWrite(OLED_RESET_PIN,HIGH);
delay(10);
}
/**
* Perform the startup operation as described by the OLED display manual. This includes
* starting a serial connection, sending a byte of 0x55 so the display can detect the baud rate,
* can finally, sending the clear screen (0x45) code.
*/
void displayInit() {
// Begin serial
Serial.print("Starting serial connection to display (baud ");
Serial.print(OLED_BAUD_RATE);
Serial.println(")");
Serial2.begin(57600);
delay(1000);
// Send baudrate id
Serial.println("Writing baudrate detection byte to display (0x55)");
Serial2.write(0x55);
readSerial(6000);
delay(1000);
// Clear the screen
Serial.println("Clearing display (0x45)");
Serial2.write(0x45);
readSerial(6000);
}
/**
* Draw a pixel at (y = 10, x = 10) with a color of white
*/
void loop(){
Serial.println("Drawing pixel to display (0x50, 0x0A, 0x0A, 0xFFFF)");
Serial2.write(0x50);
Serial2.write(0x0A);
Serial2.write(0x0A);
Serial2.write(0xFF);
Serial2.write(0xFF);
readSerial(6000);
}
/**
* Read a single byte from the serial connection with the OLED display
*
* @param timeout the amount of time to try and read the value before giving up (in milliseconds)
*
* @return the value that was read from the serial connection
*/
char readSerial(long timeout) {
long starttime = millis();
Serial.print(">> Reading serial... ");
while (Serial2.available() == 0) {
if (millis() - starttime > timeout) {
Serial.println("<ERROR: Serial Timeout>");
return 0x15;
}
}
char res = Serial2.read();
Serial.print("(Value: ");
Serial.print(res, DEC);
Serial.println(")");
return res;
}
The output from the serial monitor is as follows:
Sleeping 0
Sleeping 1
Sleeping 2
Sleeping 3
Sleeping 4
Sleeping 5
Sleeping 6
Sleeping 7
Sleeping 8
Sleeping 9
Restarting the display
Starting serial connection to display (baud 57600)
Writing baudrate detection byte to display (0x55)
>> Reading serial... <ERROR: Serial Timeout>
Clearing display (0x45)
>> Reading serial... <ERROR: Serial Timeout>
Drawing pixel to display (0x50, 0x0A, 0x0A, 0xFFFF)
>> Reading serial... <ERROR: Serial Timeout>
Drawing pixel to display (0x50, 0x0A, 0x0A, 0xFFFF)
>> Reading serial... <ERROR: Serial Timeout>
Drawing pixel to display (0x50, 0x0A, 0x0A, 0xFFFF)
>> Reading serial... <ERROR: Serial Timeout>
