CAN bus and SH1106 OLED - display not updating

[n1md4]

Hi,

I'm using several MCP2515 & TJA1050 modules to create a CAN bus network. At the moment I have 2 nodes, one creating an input and the other with the SH1106 OLED attached displaying the output.

The OLED will not update it's display.

/*

   OLED
   ===
   1....GND: (arduino pin GND)
   2....VCC: (arduino pin 5V)
   3....D0: CLK Clock (arduino pin 13)
   4....D1: MOSI data (arduino pin 11)
   5....RST: Reset (arduino pin 5)
   6....DC: data / command (arduino pin 6)
   7....CS: Chip select signal (arduino pin 7)

   CAN controller
   ===
   1....Int NC
   2....SCK (arduino pin 13)
   3....MOSI (arduino pin 11)
   4....MISO (arduino pin 12)
   5....CS (arduino pin 7)
   6....GND (arduino pin GND)
   7....Vcc (arduino pin 5V)

*/

#include "U8glib.h"            // U8glib library for the OLED
#include <SPI.h>
#include "mcp_can.h"

const int SPI_CAN_CS_PIN = 10;
MCP_CAN CAN(SPI_CAN_CS_PIN);                                    // Set CS pin

U8GLIB_SH1106_128X64 u8g(3, 4, 5);  // CS = 3, A0 = 4, RST = 5

unsigned int messageData[2];
unsigned int displayData[2];

void draw(void) {
  u8g.setFont(u8g_font_unifont);                   // select font

  u8g.setPrintPos(0,24);
  u8g.print(messageData[0]);
  Serial.println(messageData[0]);

  u8g.setPrintPos(0,48);
  u8g.print(messageData[1]);
  Serial.println(messageData[1]);*/
}

void displayVariables(void) {
  displayData[0] = messageData[0];
  displayData[1] = messageData[1];
}

void readCAN(void) {

  unsigned char messageLength = 0;
  unsigned char messageBuffer[2];

  CAN.readMsgBuf(&messageLength, messageBuffer);
  messageData[0] = CAN.getCanId();
  messageData[1] = messageBuffer[1];
}

void drawOLED(void) {
  displayVariables();
  u8g.firstPage();  
  do {
    draw();
  } while( u8g.nextPage() );
}

void setup() {

  Serial.begin(9600);
  CAN.begin(CAN_500KBPS);          // init can bus : baudrate = 500k

}

void loop() {

  readCAN();
  drawOLED();
  delay(2000);
}

Here is some testing I've done so far. What do I know…

All 7 pins need wiring in order for the OLED to function. The choice between hardware and software SPI means some devices can share pins, but still means 3 other pins will take up resources.

Despite the unresponsive nature of the OLED, the CAN messages is always being received.

If I comment out the CAN.readMsgBuf() the display updates.

With only the OLED code works perfectly.

The presence of a message sending CAN node makes no difference to the operation of the OLED, the display will not update.

Despite not operating correctly, the display does light up, it just appears to hold on to old data.

The data to display should ideally not change before being rendered, and hence the displayVariables() function.

[olikraus]

The old library u8glib does not really work together with SPI.h. Switching to u8g2 would be a much better option here. https://github.com/olikraus/U8g2_Arduino

[n1md4]

Perfect. Along with the porting guide, this now works perfectly.