Hi team! I am working on the OLED interfacing with STM32F103C8T6. All I want to do that is to display the counter value from 0 to 255 on OLED. But when I simply put the random number such as 48 it shows its equivalent ASCII value not a decimal value.

[jtron.1]

Hi team! I am working on the OLED interfacing with STM32F103C8T6. All I want to do that is to display the counter value from 0 to 255 on OLED. But when I simply put the random number such as 48 it shows its equivalent ASCII value not a decimal value as it is 48.

What is the reason of it?

I am delighted to ST community for the help.

Thanks in advance.

[Tesla DeLorean]

You've stated the symptoms twice, not sure that helps understand the cause.

Code is broken.

Show code.​

[jtron.1]

Thanks for the reply tesla.

Actually the problem is OLED shows ASCII value of decimal equivalent.

Below is the code

 //This function put the value that we want to display in my case i is the int and i=5(val) lets say

 int SSD1306_PutVal(int val, FontDef_t* Font, SSD1306_COLOR_t color) {

/* Write characters */

while (val) {

/* Write character by character */

if (SSD1306_PutV1(val, Font, color) != val) {

/* Return error */

return val;

}

/* Increase string pointer */

val++;

}

/* Everything OK, zero should be returned */

return val;

} 

//This function decide its Height and Width

int SSD1306_PutV1(int ch, FontDef_t* Font, SSD1306_COLOR_t color) {

uint32_t i, b, j;

/* Check available space in LCD */

if (

SSD1306_WIDTH <= (SSD1306.CurrentX + Font->FontWidth) ||

SSD1306_HEIGHT <= (SSD1306.CurrentY + Font->FontHeight)

) {

/* Error */

return 0;

}

/* Go through font */

for (i = 0; i < Font->FontHeight; i++) {

b = Font->data[(ch - 32) * Font->FontHeight + i];

for (j = 0; j < Font->FontWidth; j++) {

if ((b << j) & 0x8000) {

SSD1306_DrawPixel(SSD1306.CurrentX + j, (SSD1306.CurrentY + i), (SSD1306_COLOR_t) color);

} else {

SSD1306_DrawPixel(SSD1306.CurrentX + j, (SSD1306.CurrentY + i), (SSD1306_COLOR_t)!color);

}

}

}

/* Increase pointer */

SSD1306.CurrentX += Font->FontWidth;

/* Return character written */

return ch;

}

void SSD1306_UpdateScreen(void) {

uint8_t m;

for (m = 0; m < 8; m++) {

SSD1306_WRITECOMMAND(0xB0 + m); //Set Page Start

                   //Address for Page

                   //Addressing Mode

SSD1306_WRITECOMMAND(0x00);

SSD1306_WRITECOMMAND(0x10);

/* Write multi data */

ssd1306_I2C_WriteMulti(SSD1306_I2C_ADDR, 0x40, &SSD1306_Buffer[SSD1306_WIDTH * m], SSD1306_WIDTH);

}

}

void ssd1306_I2C_WriteMulti(uint8_t address, uint8_t reg, uint8_t* data, uint16_t count) {

uint8_t dt[256];

dt[0] = reg;

uint8_t i;

for(i = 0; i < count; i++)

dt[i+1] = data[i];

HAL_I2C_Master_Transmit(&hi2c1, address, dt, count+1, 10);

}

 //All the functions used below already described above

  int i;

  i=48;//When I put this value OLED shows its equivalent ASCII vale from 0123456789:

  SSD1306_GotoXY (0,0);// //function is above described

  SSD1306_PutVal ( i, &Font_11x18, 1);// //function is above described

  SSD1306_UpdateScreen(); //function is above described

  HAL_Delay (1000);

Thanks in advance.

[Tesla DeLorean]

PutVal function does not convert to a numeric value.

I​s this something you wrote or copied?

Perhaps rewrite so it does what it should.​

[jtron.1]

Yes copied code from google.

The person was showing Hello world.

I just make one change in it.

I make it int and removed pointer.

Below is the original function of PutVal()

char SSD1306_Puts(char* str, FontDef_t* Font, SSD1306_COLOR_t color) {

/* Write characters */

while (*str) {

/* Write character by character */

if (SSD1306_Putc(*str, Font, color) != *str) {

/* Return error */

return *str;

}

/* Increase string pointer */

str++;

}

/* Everything OK, zero should be returned */

return *str;

}

[Tesla DeLorean]

Create a string using itoa() or decompose to digits using basic math.

[jtron.1]

ok any link or application??

[MM..1]

This line of code explain all

b = Font->data[(ch - 32) * Font->FontHeight + i];

and you need understand font func show one character by code not numbers.

Puts prints every characters in string over cycle...usw

[Tesla DeLorean]

>>ok any link or application??

This is basic C programming and math, surely?

char string[16];

sprintf(string,"%d", val);

SSD1306_Puts (string, &Font_11x18, 1);

SSD1306_Puts (itoa(val, string, 10), &Font_11x18, 1);

char *simple_decimal_string(unsigned int x) // convert 32-bit unsigned to decimal string
{
  static char str[16]; // Enough to hold 10 digits and NUL
  char *s = str + sizeof(str);
 
  *--s = 0; // NULL at end, working backward
  do
  {
    *--s = '0' + (x % 10);
    x /= 10;
  }
  while(x);
 
  return(s);
}

SSD1306_Puts (simple_decimal_string(val), &Font_11x18, 1);

[jtron.1]

Sorry for my not availability.

Yes I will implement it today.