Help with RTC on Nucleo-F401 to display time on SSD1306 LCD

[adityapruthi01]

Hello all, 
I'm new to STM32, I have been given a project to display the time and date on either an 16x2 lcd or an oled display using the internal RTC of my board. 
I have the STM32 Nucleo f401re.
Can somebody help me?
Thanks and Regards

[mƎALLEm]

Hello @adityapruthi01 and welcome to the community,

What kind of help you are looking for? did you have an issue with a project or you didn't start at all?

Inspire from this example: https://github.com/STMicroelectronics/STM32CubeF4/tree/master/Projects/STM324xG_EVAL/Examples/RTC/RTC_Calendar

For LCD 16x2 lcd such as HD44780, you can find something on the internet:

https://community.st.com/t5/stm32-mcus-touchgfx-and-gui/i-am-trying-to-run-lcd-16x2-hd44780-using-stm32f4-discovery/td-p/382585

https://deepbluembedded.com/stm32-lcd-16x2-tutorial-library-alphanumeric-lcd-16x2-interfacing/#google_vignette

 

 

[adityapruthi01]

Hi @mƎALLEm 
Thank you so much for responding.
I did try to see some git hub repository, https://github.com/guiguitz/RTC-OLED-Application like this. 
I downloaded the zip file and from there headed to project file and ran it.

SSD1306 STM32Fxxx DESCRIPTION

VCC	3.3V-5V	-
GND	GND	-
SCL	PB6-PB8	Serial clock line
SDA	PB7-PB9	Serial data line

I connected the oled as mentioned inside the repository for configuring the oled with my board.
I tried to run this on the STM32 Cube IDE but the oled won't turn on.
I don't even know what this code does.
Thanks for the links, i will just take a look.

[mƎALLEm]

Check your connections, wiring continuity, the LCD power supply etc .. This is what you need to do as a first step, then with a logic analyzer check SDA, SCL signals.

Otherwise, contact the developers.

[Andrew Neil]

Welcome to the forum

 

---

@adityapruthi01 wrote:

I'm new to STM32

---

Do you have any experience with any other microcontrollers? With programming in general?

 

---

@adityapruthi01 wrote:

I have been given a project to display the time and date on either an 16x2 lcd or an oled display using the internal RTC of my board. 

---

So what have you tried so far?

Should be RTC examples available for the Nucleo f401re ...

https://www.youtube.com/watch?v=pkT1asykALk

https://www.youtube.com/watch?v=eumKLXNlM0U

https://www.youtube.com/watch?v=gL8OoS9E1rw&list=PLnMKNibPkDnFCosVVv98U5dCulE6T3Iy8&pp=iAQB

[adityapruthi01]

Hi @Andrew Neil, 
Thanks for replying.
Yes, I do have some experience with arduino board and esp boards, but only upto arduino IDE.
Thanks for the videos of the introductions.
But if you do have any content for using oled with the board and displaying the real time, on the oled, it will be very helpful for me. 
Thanking you for you response.
Regards

[mƎALLEm]

---

@adityapruthi01 wrote:

But if you do have any content for using oled with the board and displaying the real time, on the oled, it will be very helpful for me. 

---

Forget about RTC for now and try to display something on the LCD by using the driver provided in the link you shared.

These four files are needed to handle the LCD:

https://github.com/guiguitz/RTC-OLED-Application/blob/main/NUCLEO-F401RE-RTC-OLED-Application/Src/ssd1306.c

https://github.com/guiguitz/RTC-OLED-Application/blob/main/NUCLEO-F401RE-RTC-OLED-Application/Src/fonts.c

https://github.com/guiguitz/RTC-OLED-Application/blob/main/NUCLEO-F401RE-RTC-OLED-Application/Inc/ssd1306.h

https://github.com/guiguitz/RTC-OLED-Application/blob/main/NUCLEO-F401RE-RTC-OLED-Application/Inc/fonts.h

 

[adityapruthi01]

Hello all, (EDITED)
With some debugging i've got the code to work without any errors, everything is working fine on the OLED Display,the only problem is if I am coommenting out this line:

 

void HAL_TIM_PeriodElapsedCallback(TIM_HandleTypeDef *htim)
{
 if (htim->Instance == TIM3)
 {
 // Your 1-second interrupt handling code here
 	Print_Date_Oled();
 	Print_Time_Oled();
 }
}​

 

which is used to display the time and date on the OLED, the Terra Term does not work and there is no feedback when pressing any keys while trying to change the date and time.

The above is showing like this when trying to press any key on the num pad.

But actually it has to be like this.

The above happens when I commenting out the Print date and time function.

So either I am able to use the RTC functionality or miss displaying it on the OLED, or I am able to Display on the OLED missing RTC functionality.
The video for the same can be found here https://www.youtube.com/watch?v=Nm-16YhCYl8&t=1438s
Github for the same original project is located here: https://github.com/PRTechTalk/STM32/tree/main/G071_LCD_RTC.

Can you please check.
Thanks and Regards

The whole code that I am dumping to my STM Nucleo Board can be found below:

 

#include "ssd1306.h"
#include <math.h>
#include <stdlib.h>
#include <string.h> // For memcpy

#if defined(SSD1306_USE_I2C)

void ssd1306_Reset(void) {
 /* for I2C - do nothing */
}

// Send a byte to the command register
void ssd1306_WriteCommand(uint8_t byte) {
 HAL_I2C_Mem_Write(&SSD1306_I2C_PORT, SSD1306_I2C_ADDR, 0x00, 1, &byte, 1, HAL_MAX_DELAY);
}

// Send data
void ssd1306_WriteData(uint8_t* buffer, size_t buff_size) {
 HAL_I2C_Mem_Write(&SSD1306_I2C_PORT, SSD1306_I2C_ADDR, 0x40, 1, buffer, buff_size, HAL_MAX_DELAY);
}

#elif defined(SSD1306_USE_SPI)

void ssd1306_Reset(void) {
 // CS = High (not selected)
 HAL_GPIO_WritePin(SSD1306_CS_Port, SSD1306_CS_Pin, GPIO_PIN_SET);

 // Reset the OLED
 HAL_GPIO_WritePin(SSD1306_Reset_Port, SSD1306_Reset_Pin, GPIO_PIN_RESET);
 HAL_Delay(10);
 HAL_GPIO_WritePin(SSD1306_Reset_Port, SSD1306_Reset_Pin, GPIO_PIN_SET);
 HAL_Delay(10);
}

// Send a byte to the command register
void ssd1306_WriteCommand(uint8_t byte) {
 HAL_GPIO_WritePin(SSD1306_CS_Port, SSD1306_CS_Pin, GPIO_PIN_RESET); // select OLED
 HAL_GPIO_WritePin(SSD1306_DC_Port, SSD1306_DC_Pin, GPIO_PIN_RESET); // command
 HAL_SPI_Transmit(&SSD1306_SPI_PORT, (uint8_t *) &byte, 1, HAL_MAX_DELAY);
 HAL_GPIO_WritePin(SSD1306_CS_Port, SSD1306_CS_Pin, GPIO_PIN_SET); // un-select OLED
}

// Send data
void ssd1306_WriteData(uint8_t* buffer, size_t buff_size) {
 HAL_GPIO_WritePin(SSD1306_CS_Port, SSD1306_CS_Pin, GPIO_PIN_RESET); // select OLED
 HAL_GPIO_WritePin(SSD1306_DC_Port, SSD1306_DC_Pin, GPIO_PIN_SET); // data
 HAL_SPI_Transmit(&SSD1306_SPI_PORT, buffer, buff_size, HAL_MAX_DELAY);
 HAL_GPIO_WritePin(SSD1306_CS_Port, SSD1306_CS_Pin, GPIO_PIN_SET); // un-select OLED
}

#else
#error "You should define SSD1306_USE_SPI or SSD1306_USE_I2C macro"
#endif


// Screenbuffer
static uint8_t SSD1306_Buffer[SSD1306_BUFFER_SIZE];

// Screen object
static SSD1306_t SSD1306;

/* Fills the Screenbuffer with values from a given buffer of a fixed length */
SSD1306_Error_t ssd1306_FillBuffer(uint8_t* buf, uint32_t len) {
 SSD1306_Error_t ret = SSD1306_ERR;
 if (len <= SSD1306_BUFFER_SIZE) {
 memcpy(SSD1306_Buffer,buf,len);
 ret = SSD1306_OK;
 }
 return ret;
}

/* Initialize the oled screen */
void ssd1306_Init(void) {
 // Reset OLED
 ssd1306_Reset();

 // Wait for the screen to boot
 HAL_Delay(100);

 // Init OLED
 ssd1306_SetDisplayOn(0); //display off

 ssd1306_WriteCommand(0x20); //Set Memory Addressing Mode
 ssd1306_WriteCommand(0x00); // 00b,Horizontal Addressing Mode; 01b,Vertical Addressing Mode;
 // 10b,Page Addressing Mode (RESET); 11b,Invalid

 ssd1306_WriteCommand(0xB0); //Set Page Start Address for Page Addressing Mode,0-7

#ifdef SSD1306_MIRROR_VERT
 ssd1306_WriteCommand(0xC0); // Mirror vertically
#else
 ssd1306_WriteCommand(0xC8); //Set COM Output Scan Direction
#endif

 ssd1306_WriteCommand(0x00); //---set low column address
 ssd1306_WriteCommand(0x10); //---set high column address

 ssd1306_WriteCommand(0x40); //--set start line address - CHECK

 ssd1306_SetContrast(0xFF);

#ifdef SSD1306_MIRROR_HORIZ
 ssd1306_WriteCommand(0xA0); // Mirror horizontally
#else
 ssd1306_WriteCommand(0xA1); //--set segment re-map 0 to 127 - CHECK
#endif

#ifdef SSD1306_INVERSE_COLOR
 ssd1306_WriteCommand(0xA7); //--set inverse color
#else
 ssd1306_WriteCommand(0xA6); //--set normal color
#endif

// Set multiplex ratio.
#if (SSD1306_HEIGHT == 128)
 // Found in the Luma Python lib for SH1106.
 ssd1306_WriteCommand(0xFF);
#else
 ssd1306_WriteCommand(0xA8); //--set multiplex ratio(1 to 64) - CHECK
#endif

#if (SSD1306_HEIGHT == 32)
 ssd1306_WriteCommand(0x1F); //
#elif (SSD1306_HEIGHT == 64)
 ssd1306_WriteCommand(0x3F); //
#elif (SSD1306_HEIGHT == 128)
 ssd1306_WriteCommand(0x3F); // Seems to work for 128px high displays too.
#else
#error "Only 32, 64, or 128 lines of height are supported!"
#endif

 ssd1306_WriteCommand(0xA4); //0xa4,Output follows RAM content;0xa5,Output ignores RAM content

 ssd1306_WriteCommand(0xD3); //-set display offset - CHECK
 ssd1306_WriteCommand(0x00); //-not offset

 ssd1306_WriteCommand(0xD5); //--set display clock divide ratio/oscillator frequency
 ssd1306_WriteCommand(0xF0); //--set divide ratio

 ssd1306_WriteCommand(0xD9); //--set pre-charge period
 ssd1306_WriteCommand(0x22); //

 ssd1306_WriteCommand(0xDA); //--set com pins hardware configuration - CHECK
#if (SSD1306_HEIGHT == 32)
 ssd1306_WriteCommand(0x02);
#elif (SSD1306_HEIGHT == 64)
 ssd1306_WriteCommand(0x12);
#elif (SSD1306_HEIGHT == 128)
 ssd1306_WriteCommand(0x12);
#else
#error "Only 32, 64, or 128 lines of height are supported!"
#endif

 ssd1306_WriteCommand(0xDB); //--set vcomh
 ssd1306_WriteCommand(0x20); //0x20,0.77xVcc

 ssd1306_WriteCommand(0x8D); //--set DC-DC enable
 ssd1306_WriteCommand(0x14); //
 ssd1306_SetDisplayOn(1); //--turn on SSD1306 panel

 // Clear screen
 ssd1306_Fill(Black);
 
 // Flush buffer to screen
 ssd1306_UpdateScreen();
 
 // Set default values for screen object
 SSD1306.CurrentX = 0;
 SSD1306.CurrentY = 0;
 
 SSD1306.Initialized = 1;
}

/* Fill the whole screen with the given color */
void ssd1306_Fill(SSD1306_COLOR color) {
 memset(SSD1306_Buffer, (color == Black) ? 0x00 : 0xFF, sizeof(SSD1306_Buffer));
}

/* Write the screenbuffer with changed to the screen */
void ssd1306_UpdateScreen(void) {
 // Write data to each page of RAM. Number of pages
 // depends on the screen height:
 //
 // * 32px == 4 pages
 // * 64px == 8 pages
 // * 128px == 16 pages
 for(uint8_t i = 0; i < SSD1306_HEIGHT/8; i++) {
 ssd1306_WriteCommand(0xB0 + i); // Set the current RAM page address.
 ssd1306_WriteCommand(0x00 + SSD1306_X_OFFSET_LOWER);
 ssd1306_WriteCommand(0x10 + SSD1306_X_OFFSET_UPPER);
 ssd1306_WriteData(&SSD1306_Buffer[SSD1306_WIDTH*i],SSD1306_WIDTH);
 }
}

/*
 * Draw one pixel in the screenbuffer
 * X => X Coordinate
 * Y => Y Coordinate
 * color => Pixel color
 */
void ssd1306_DrawPixel(uint8_t x, uint8_t y, SSD1306_COLOR color) {
 if(x >= SSD1306_WIDTH || y >= SSD1306_HEIGHT) {
 // Don't write outside the buffer
 return;
 }
 
 // Draw in the right color
 if(color == White) {
 SSD1306_Buffer[x + (y / 8) * SSD1306_WIDTH] |= 1 << (y % 8);
 } else { 
 SSD1306_Buffer[x + (y / 8) * SSD1306_WIDTH] &= ~(1 << (y % 8));
 }
}

/*
 * Draw 1 char to the screen buffer
 * ch => char om weg te schrijven
 * Font => Font waarmee we gaan schrijven
 * color => Black or White
 */
char ssd1306_WriteChar(char ch, SSD1306_Font_t Font, SSD1306_COLOR color) {
 uint32_t i, b, j;
 
 // Check if character is valid
 if (ch < 32 || ch > 126)
 return 0;
 
 // Check remaining space on current line
 if (SSD1306_WIDTH < (SSD1306.CurrentX + Font.width) ||
 SSD1306_HEIGHT < (SSD1306.CurrentY + Font.height))
 {
 // Not enough space on current line
 return 0;
 }
 
 // Use the font to write
 for(i = 0; i < Font.height; i++) {
 b = Font.data[(ch - 32) * Font.height + i];
 for(j = 0; j < Font.width; j++) {
 if((b << j) & 0x8000) {
 ssd1306_DrawPixel(SSD1306.CurrentX + j, (SSD1306.CurrentY + i), (SSD1306_COLOR) color);
 } else {
 ssd1306_DrawPixel(SSD1306.CurrentX + j, (SSD1306.CurrentY + i), (SSD1306_COLOR)!color);
 }
 }
 }
 
 // The current space is now taken
 SSD1306.CurrentX += Font.char_width ? Font.char_width[ch - 32] : Font.width;
 
 // Return written char for validation
 return ch;
}

/* Write full string to screenbuffer */
char ssd1306_WriteString(char* str, SSD1306_Font_t Font, SSD1306_COLOR color) {
 while (*str) {
 if (ssd1306_WriteChar(*str, Font, color) != *str) {
 // Char could not be written
 return *str;
 }
 str++;
 }
 
 // Everything ok
 return *str;
}

/* Position the cursor */
void ssd1306_SetCursor(uint8_t x, uint8_t y) {
 SSD1306.CurrentX = x;
 SSD1306.CurrentY = y;
}

/* Draw line by Bresenhem's algorithm */
void ssd1306_Line(uint8_t x1, uint8_t y1, uint8_t x2, uint8_t y2, SSD1306_COLOR color) {
 int32_t deltaX = abs(x2 - x1);
 int32_t deltaY = abs(y2 - y1);
 int32_t signX = ((x1 < x2) ? 1 : -1);
 int32_t signY = ((y1 < y2) ? 1 : -1);
 int32_t error = deltaX - deltaY;
 int32_t error2;
 
 ssd1306_DrawPixel(x2, y2, color);

 while((x1 != x2) || (y1 != y2)) {
 ssd1306_DrawPixel(x1, y1, color);
 error2 = error * 2;
 if(error2 > -deltaY) {
 error -= deltaY;
 x1 += signX;
 }
 
 if(error2 < deltaX) {
 error += deltaX;
 y1 += signY;
 }
 }
 return;
}

/* Draw polyline */
void ssd1306_Polyline(const SSD1306_VERTEX *par_vertex, uint16_t par_size, SSD1306_COLOR color) {
 uint16_t i;
 if(par_vertex == NULL) {
 return;
 }

 for(i = 1; i < par_size; i++) {
 ssd1306_Line(par_vertex[i - 1].x, par_vertex[i - 1].y, par_vertex[i].x, par_vertex[i].y, color);
 }

 return;
}

/* Convert Degrees to Radians */
static float ssd1306_DegToRad(float par_deg) {
 return par_deg * (3.14f / 180.0f);
}

/* Normalize degree to [0;360] */
static uint16_t ssd1306_NormalizeTo0_360(uint16_t par_deg) {
 uint16_t loc_angle;
 if(par_deg <= 360) {
 loc_angle = par_deg;
 } else {
 loc_angle = par_deg % 360;
 loc_angle = (loc_angle ? loc_angle : 360);
 }
 return loc_angle;
}

/*
 * DrawArc. Draw angle is beginning from 4 quart of trigonometric circle (3pi/2)
 * start_angle in degree
 * sweep in degree
 */
void ssd1306_DrawArc(uint8_t x, uint8_t y, uint8_t radius, uint16_t start_angle, uint16_t sweep, SSD1306_COLOR color) {
 static const uint8_t CIRCLE_APPROXIMATION_SEGMENTS = 36;
 float approx_degree;
 uint32_t approx_segments;
 uint8_t xp1,xp2;
 uint8_t yp1,yp2;
 uint32_t count;
 uint32_t loc_sweep;
 float rad;
 
 loc_sweep = ssd1306_NormalizeTo0_360(sweep);
 
 count = (ssd1306_NormalizeTo0_360(start_angle) * CIRCLE_APPROXIMATION_SEGMENTS) / 360;
 approx_segments = (loc_sweep * CIRCLE_APPROXIMATION_SEGMENTS) / 360;
 approx_degree = loc_sweep / (float)approx_segments;
 while(count < approx_segments)
 {
 rad = ssd1306_DegToRad(count*approx_degree);
 xp1 = x + (int8_t)(sinf(rad)*radius);
 yp1 = y + (int8_t)(cosf(rad)*radius); 
 count++;
 if(count != approx_segments) {
 rad = ssd1306_DegToRad(count*approx_degree);
 } else {
 rad = ssd1306_DegToRad(loc_sweep);
 }
 xp2 = x + (int8_t)(sinf(rad)*radius);
 yp2 = y + (int8_t)(cosf(rad)*radius); 
 ssd1306_Line(xp1,yp1,xp2,yp2,color);
 }
 
 return;
}

/*
 * Draw arc with radius line
 * Angle is beginning from 4 quart of trigonometric circle (3pi/2)
 * start_angle: start angle in degree
 * sweep: finish angle in degree
 */
void ssd1306_DrawArcWithRadiusLine(uint8_t x, uint8_t y, uint8_t radius, uint16_t start_angle, uint16_t sweep, SSD1306_COLOR color) {
 const uint32_t CIRCLE_APPROXIMATION_SEGMENTS = 36;
 float approx_degree;
 uint32_t approx_segments;
 uint8_t xp1;
 uint8_t xp2 = 0;
 uint8_t yp1;
 uint8_t yp2 = 0;
 uint32_t count;
 uint32_t loc_sweep;
 float rad;
 
 loc_sweep = ssd1306_NormalizeTo0_360(sweep);
 
 count = (ssd1306_NormalizeTo0_360(start_angle) * CIRCLE_APPROXIMATION_SEGMENTS) / 360;
 approx_segments = (loc_sweep * CIRCLE_APPROXIMATION_SEGMENTS) / 360;
 approx_degree = loc_sweep / (float)approx_segments;

 rad = ssd1306_DegToRad(count*approx_degree);
 uint8_t first_point_x = x + (int8_t)(sinf(rad)*radius);
 uint8_t first_point_y = y + (int8_t)(cosf(rad)*radius); 
 while (count < approx_segments) {
 rad = ssd1306_DegToRad(count*approx_degree);
 xp1 = x + (int8_t)(sinf(rad)*radius);
 yp1 = y + (int8_t)(cosf(rad)*radius); 
 count++;
 if (count != approx_segments) {
 rad = ssd1306_DegToRad(count*approx_degree);
 } else {
 rad = ssd1306_DegToRad(loc_sweep);
 }
 xp2 = x + (int8_t)(sinf(rad)*radius);
 yp2 = y + (int8_t)(cosf(rad)*radius); 
 ssd1306_Line(xp1,yp1,xp2,yp2,color);
 }
 
 // Radius line
 ssd1306_Line(x,y,first_point_x,first_point_y,color);
 ssd1306_Line(x,y,xp2,yp2,color);
 return;
}

/* Draw circle by Bresenhem's algorithm */
void ssd1306_DrawCircle(uint8_t par_x,uint8_t par_y,uint8_t par_r,SSD1306_COLOR par_color) {
 int32_t x = -par_r;
 int32_t y = 0;
 int32_t err = 2 - 2 * par_r;
 int32_t e2;

 if (par_x >= SSD1306_WIDTH || par_y >= SSD1306_HEIGHT) {
 return;
 }

 do {
 ssd1306_DrawPixel(par_x - x, par_y + y, par_color);
 ssd1306_DrawPixel(par_x + x, par_y + y, par_color);
 ssd1306_DrawPixel(par_x + x, par_y - y, par_color);
 ssd1306_DrawPixel(par_x - x, par_y - y, par_color);
 e2 = err;

 if (e2 <= y) {
 y++;
 err = err + (y * 2 + 1);
 if(-x == y && e2 <= x) {
 e2 = 0;
 }
 }

 if (e2 > x) {
 x++;
 err = err + (x * 2 + 1);
 }
 } while (x <= 0);

 return;
}

/* Draw filled circle. Pixel positions calculated using Bresenham's algorithm */
void ssd1306_FillCircle(uint8_t par_x,uint8_t par_y,uint8_t par_r,SSD1306_COLOR par_color) {
 int32_t x = -par_r;
 int32_t y = 0;
 int32_t err = 2 - 2 * par_r;
 int32_t e2;

 if (par_x >= SSD1306_WIDTH || par_y >= SSD1306_HEIGHT) {
 return;
 }

 do {
 for (uint8_t _y = (par_y + y); _y >= (par_y - y); _y--) {
 for (uint8_t _x = (par_x - x); _x >= (par_x + x); _x--) {
 ssd1306_DrawPixel(_x, _y, par_color);
 }
 }

 e2 = err;
 if (e2 <= y) {
 y++;
 err = err + (y * 2 + 1);
 if (-x == y && e2 <= x) {
 e2 = 0;
 }
 }

 if (e2 > x) {
 x++;
 err = err + (x * 2 + 1);
 }
 } while (x <= 0);

 return;
}

/* Draw a rectangle */
void ssd1306_DrawRectangle(uint8_t x1, uint8_t y1, uint8_t x2, uint8_t y2, SSD1306_COLOR color) {
 ssd1306_Line(x1,y1,x2,y1,color);
 ssd1306_Line(x2,y1,x2,y2,color);
 ssd1306_Line(x2,y2,x1,y2,color);
 ssd1306_Line(x1,y2,x1,y1,color);

 return;
}

/* Draw a filled rectangle */
void ssd1306_FillRectangle(uint8_t x1, uint8_t y1, uint8_t x2, uint8_t y2, SSD1306_COLOR color) {
 uint8_t x_start = ((x1<=x2) ? x1 : x2);
 uint8_t x_end = ((x1<=x2) ? x2 : x1);
 uint8_t y_start = ((y1<=y2) ? y1 : y2);
 uint8_t y_end = ((y1<=y2) ? y2 : y1);

 for (uint8_t y= y_start; (y<= y_end)&&(y<SSD1306_HEIGHT); y++) {
 for (uint8_t x= x_start; (x<= x_end)&&(x<SSD1306_WIDTH); x++) {
 ssd1306_DrawPixel(x, y, color);
 }
 }
 return;
}

SSD1306_Error_t ssd1306_InvertRectangle(uint8_t x1, uint8_t y1, uint8_t x2, uint8_t y2) {
 if ((x2 >= SSD1306_WIDTH) || (y2 >= SSD1306_HEIGHT)) {
 return SSD1306_ERR;
 }
 if ((x1 > x2) || (y1 > y2)) {
 return SSD1306_ERR;
 }
 uint32_t i;
 if ((y1 / 8) != (y2 / 8)) {
 /* if rectangle doesn't lie on one 8px row */
 for (uint32_t x = x1; x <= x2; x++) {
 i = x + (y1 / 8) * SSD1306_WIDTH;
 SSD1306_Buffer[i] ^= 0xFF << (y1 % 8);
 i += SSD1306_WIDTH;
 for (; i < x + (y2 / 8) * SSD1306_WIDTH; i += SSD1306_WIDTH) {
 SSD1306_Buffer[i] ^= 0xFF;
 }
 SSD1306_Buffer[i] ^= 0xFF >> (7 - (y2 % 8));
 }
 } else {
 /* if rectangle lies on one 8px row */
 const uint8_t mask = (0xFF << (y1 % 8)) & (0xFF >> (7 - (y2 % 8)));
 for (i = x1 + (y1 / 8) * SSD1306_WIDTH;
 i <= (uint32_t)x2 + (y2 / 8) * SSD1306_WIDTH; i++) {
 SSD1306_Buffer[i] ^= mask;
 }
 }
 return SSD1306_OK;
}

/* Draw a bitmap */
void ssd1306_DrawBitmap(uint8_t x, uint8_t y, const unsigned char* bitmap, uint8_t w, uint8_t h, SSD1306_COLOR color) {
 int16_t byteWidth = (w + 7) / 8; // Bitmap scanline pad = whole byte
 uint8_t byte = 0;

 if (x >= SSD1306_WIDTH || y >= SSD1306_HEIGHT) {
 return;
 }

 for (uint8_t j = 0; j < h; j++, y++) {
 for (uint8_t i = 0; i < w; i++) {
 if (i & 7) {
 byte <<= 1;
 } else {
 byte = (*(const unsigned char *)(&bitmap[j * byteWidth + i / 8]));
 }

 if (byte & 0x80) {
 ssd1306_DrawPixel(x + i, y, color);
 }
 }
 }
 return;
}

void ssd1306_SetContrast(const uint8_t value) {
 const uint8_t kSetContrastControlRegister = 0x81;
 ssd1306_WriteCommand(kSetContrastControlRegister);
 ssd1306_WriteCommand(value);
}

void ssd1306_SetDisplayOn(const uint8_t on) {
 uint8_t value;
 if (on) {
 value = 0xAF; // Display on
 SSD1306.DisplayOn = 1;
 } else {
 value = 0xAE; // Display off
 SSD1306.DisplayOn = 0;
 }
 ssd1306_WriteCommand(value);
}

uint8_t ssd1306_GetDisplayOn() {
 return SSD1306.DisplayOn;
}

 

 

 

 

 

 

[Andrew Neil]

Please see the Posting Tips for how to properly post source code:

https://community.st.com/t5/community-guidelines/how-to-write-your-question-to-maximize-your-chances-to-find-a/ta-p/575228

I edited your post for you

[adityapruthi01]

Thanks alot @Andrew Neil, 
Will take care of this in future. 
Regards