I'm trying to get going with this i2c display device: https://www.newhavendisplay.com/specs/NHD-C160100DiZ-FSW-FBW.pdf

On Arduino, I've been able to initialise the device using the wire library and the following code:

#include <Wire.h>

#define Addr 0x3F 

const int resetPin = 2;       
const int chipSelectPin = 3;  
const char comsend = 0x00;

void DiZ_init()
{
  Wire.beginTransmission(Addr);
  Wire.write(comsend);
  Wire.write(0x38); //mode set
  Wire.write(0x04); //FR[3:0] = 0000, BE = 1, EXT = 0 (normal instruction mode)
  Wire.write(0xAB); //OSC ON
  Wire.write(0x66); //set DC-DC step up
  Wire.write(0x26); //set regulator resistor
  Wire.write(0x81); //set reference voltage select mode
  Wire.write(0x1C); //set reference voltage register
  Wire.write(0x56); //set 1/11 bias
  Wire.write(0x2C); //set power control
  Wire.write(0x2E); //set power control
  Wire.write(0x2F); //set power control
  Wire.write(0xAF); //display ON
  Wire.endTransmission();
}

void setup()
{
  pinMode(resetPin, OUTPUT);
  pinMode(chipSelectPin, OUTPUT);
  digitalWrite(chipSelectPin, LOW);
  digitalWrite(resetPin, LOW);
  
  delay(150);
  digitalWrite(resetPin, HIGH);
  delay(150);
  
  Wire.begin();
  delay(5);

  DiZ_init();
}

I'm now trying to communicate with the device using Bela, but so far to no avail. I've tried to recreate the Arduino code exactly - here are the relevant bits from my render.cpp:

#include "Display.h"

#define DISPLAY_CHIP_SEL_PIN P9_12
#define DISPLAY_RESET_PIN P9_14

Display display;

bool setup(BelaContext *context, void *userData)
{
	pinMode(context, 0, DISPLAY_CHIP_SEL_PIN, OUTPUT);
   	pinMode(context, 0, DISPLAY_RESET_PIN, OUTPUT);
    	
    digitalWrite(context, 0, DISPLAY_CHIP_SEL_PIN, GPIO_LOW);
    digitalWrite(context, 0, DISPLAY_RESET_PIN, GPIO_LOW);
    
  	usleep(150000);
  	digitalWrite(context, 0, DISPLAY_RESET_PIN, GPIO_HIGH);
  	usleep(150000);
    
	if(!display.begin())
	{
		rt_printf("Error initialising Newhaven display device\n");
	}
	
	usleep(5000);
	int result = display.initDisplay();
	usleep(5000);
	
	rt_printf("result = %d\n", result);
	return true;
}

and Display.cpp

const char COM_SEND = 0x00;

boolean Display::begin(uint8_t bus, uint8_t i2caddr) 
{
    mI2c_address = i2caddr;
    
    if(initI2C_RW(bus, i2caddr, 0) > 0)
        return false;

    return true;
}

int Display::initDisplay()
{
	uint8_t initTable[] = {COM_SEND, 0x38, 0x04, 0xAB, 0x66, 0x26, 0x81, 0x1C, 0x56, 0x2C, 0x2E, 0x2F, 0xAF};
	int result = write(i2C_file, initTable, 13);
	return result;
}

If I run i2cdetect -y -r 1 on the command line once the reset pin is set high, the device (0x3f) is found, so I assume it's a problem with my code and not the hardware/connections.

The result returned by initDisplay is -1. From the Bela i2c example class (I2C_MPR121) I gathered that the write(i2C_file...) method could be used to transmit individual bytes in the same way as Wire.write() on Arduino, but perhaps I have misunderstood?