Howdy!
I'm developing a project in which I want to use 4 OLED displays (the cheap I2C ones, as found here: Amazon.com ) to display unique messages. I'm working off of an Arduino UNO, and I am using a multiplexer (found here: DssCircuits.com is for sale | HugeDomains ) to send a unique I2C signal to each of the four screens. You can see my actual setup in the photos I've attached below (don't judge me too hard for the shoddy soldering job).
As I have it currently set up, power is going from the Arduino to the multiplexer, as well as to all four screens. The SDA/SCL lines are fed from the Arduino's A4/A5 pins to the multiplexer's input pins, and then SDA0/SCL0 through SDA3/SCL3 are sent to their respective screens. On each screen, a 4.7k resistor is placed between the VCC line and both the SDA and SCL lines. My code is a modified version of the sample sketch you can download from the multiplexer's product page, and additionally uses the u8glib to process fonts/text. I'll paste it at the bottom.
My issue is this: When I run the code, only the first screen lights up with the correct message, but the other three stay dark. At first I thought it was an issue with the multiplexer, but if I disconnect the two I2C lines from the working screen and replace them with any other screen's I2C lines, the proper message for that new line is displayed ("second", "third", "fourth"). This is the case no matter what screen begins with the first I2C lines coming from the mux (SDA0/SCL0), so it isn't an issue with how they are wired for power, either.
Can anyone help out with this? I've been beating my head against a wall for quite a while now, for a task that shouldn't be all that unusual to do. Thanks in advance!
P.S. for background on how I started out, see the post I made a couple weeks ago on the "networking" board: Sending unique information to 4 OLED displays with I2C? - Networking, Protocols, and Devices - Arduino Forum
aaaaaaand, here's my code:
#include "Wire.h"
#include "U8glib.h"
U8GLIB_SSD1306_128X64 u8g(U8G_I2C_OPT_NONE); // I2C / TWI
#define MUX 0x70 //Multiplexer Address
#define DISPLAY 0x3C //OLED Display Address
void draw(char str[]) {
// graphic commands to redraw the complete screen should be placed here
u8g.setFont(u8g_font_fur17);
u8g.drawStr( 5, 40, str);
}
void setup()
{
/* U8G portion */
// assign default color value
if ( u8g.getMode() == U8G_MODE_R3G3B2 ) {
u8g.setColorIndex(255); // white
}
else if ( u8g.getMode() == U8G_MODE_GRAY2BIT ) {
u8g.setColorIndex(3); // max intensity
}
else if ( u8g.getMode() == U8G_MODE_BW ) {
u8g.setColorIndex(1); // pixel on
}
else if ( u8g.getMode() == U8G_MODE_HICOLOR ) {
u8g.setHiColorByRGB(255,255,255);
}
/* MUX Example portion */
Wire.begin();
Serial.begin(115200);
mux(0); //select Display on channel 0
initializeDISP(DISPLAY);
mux(1); //select Display on channel 1
initializeDISP(DISPLAY);
mux(2); //select Display on channel 2
initializeDISP(DISPLAY);
mux(3); //select Display on channel 3
initializeDISP(DISPLAY);
mux(0xFF); //disable all channels. This is not required
}
void loop()
{
if (screen == 1) {
mux(0);
sendDISP(DISPLAY, "first");
mux(1);
sendDISP(DISPLAY, "second");
mux(2);
sendDISP(DISPLAY, "third");
mux(3);
sendDISP(DISPLAY, "fourth");
mux(0xFF);
}
delay(3000);
}
/********************************************************
* When selecting a channel bit2 of the control register
* must be set to a logic 1 to enable channel selection.
* If bit2 is a logic zero then all channels will be disabled.
* If 0xFF is the selected channel it will disable all channels.
********************************************************/
void mux(byte channel)
{
byte controlRegister = 0x04;
controlRegister |= channel;
Wire.beginTransmission(MUX);
if (channel == 0xFF){Wire.write(0x00);} //deselect all channels
else {Wire.write(controlRegister);} //set to selected channel
Wire.endTransmission();
}
void initializeDISP(uint8_t address)
{
Serial.println("Initiating Quick Start");
Wire.beginTransmission(DISPLAY);
Wire.write(0x06);
Wire.write(0x40);
Wire.write(0x00);
Wire.endTransmission();
}
void sendDISP(int _disp, char rootStr[])
{
/* Not sure what these lines are for... */
Wire.beginTransmission(_disp);
Wire.write(0x04);
Wire.endTransmission();
// picture loop
u8g.firstPage();
do {
draw(rootStr);
} while( u8g.nextPage() );
}
