[ARM] 18B20 not read, on tft only show 000.0625 C

[betuse]

Hi for all,
I use EasyMx Pro for Stellaris board with LM4F232 (Cortex M4) mcu,
I need to read temp from 18B20, but on TFT I only have 000.0625 C,
sensor in connected on PD4 port
the code is

// TFT module connections
char TFT_DataPort at GPIO_PORTJ_DATA;
sbit TFT_RST at GPIO_PORTH_DATA5_bit;
sbit TFT_RS at GPIO_PORTG_DATA7_bit;
sbit TFT_CS at GPIO_PORTH_DATA6_bit;
sbit TFT_RD at GPIO_PORTC_DATA5_bit;
sbit TFT_WR at GPIO_PORTH_DATA4_bit;
sbit TFT_BLED at GPIO_PORTA_DATA3_bit;
char TFT_DataPort_Direction at GPIO_PORTJ_DIR;
sbit TFT_RST_Direction at GPIO_PORTH_DIR5_bit;
sbit TFT_RS_Direction at GPIO_PORTG_DIR7_bit;
sbit TFT_CS_Direction at GPIO_PORTH_DIR6_bit;
sbit TFT_RD_Direction at GPIO_PORTC_DIR5_bit;
sbit TFT_WR_Direction at GPIO_PORTH_DIR4_bit;
sbit TFT_BLED_Direction at GPIO_PORTA_DIR3_bit;
// End TFT module connections

//  Set TEMP_RESOLUTION to the corresponding resolution of used DS18x20 sensor:
//  18S20: 9  (default setting; can be 9,10,11,or 12)
//  18B20: 12

const unsigned short TEMP_RESOLUTION = 12;
char *text = "000.0000  C";
unsigned temp;

void DrawScr() {
  TFT_Init_ILI9341_8bit(320, 240);
  TFT_Fill_Screen(CL_WHITE);
  TFT_Set_Pen(CL_Black, 2);
  TFT_Line(20, 220, 300, 220);
  TFT_LIne(20,  46, 300,  46);
  TFT_Set_Font(&HandelGothic_BT21x22_Regular, CL_RED, FO_HORIZONTAL);
  TFT_Write_Text("Temperature sensor (18B20)", 20, 14);
  TFT_Set_Font(&Verdana12x13_Regular, CL_RED, FO_HORIZONTAL);
  TFT_Write_Text("Cortex M4", 19, 223);
  TFT_Set_Font(&Verdana12x13_Regular, CL_RED, FO_HORIZONTAL);
  TFT_Write_Text("LM4F232", 256, 223);
  TFT_Set_Font(&TFT_defaultFont, CL_BLACK, FO_HORIZONTAL);
}

void Display_Temperature(unsigned int temp2write) {
  const unsigned short RES_SHIFT = TEMP_RESOLUTION - 8;
  char temp_whole;
  unsigned int temp_fraction;

  // Check if temperature is negative
  if (temp2write & 0x8000) {
    text[0] = '-';
    temp2write = ~temp2write + 1;
  }

  // Extract temp_whole
  temp_whole = temp2write >> RES_SHIFT ;

  // Convert temp_whole to characters
  if (temp_whole/100)
    text[0] = temp_whole/100  + 48;
  else
    text[0] = '0';

  text[1] = (temp_whole/10)%10 + 48;             // Extract tens digit
  text[2] =  temp_whole%10     + 48;             // Extract ones digit

  // Extract temp_fraction and convert it to unsigned int
  temp_fraction  = temp2write << (4-RES_SHIFT);
  temp_fraction &= 0x000F;
  temp_fraction *= 625;

  // Convert temp_fraction to characters
  text[4] =  temp_fraction/1000    + 48;         // Extract thousands digit
  text[5] = (temp_fraction/100)%10 + 48;         // Extract hundreds digit
  text[6] = (temp_fraction/10)%10  + 48;         // Extract tens digit
  text[7] =  temp_fraction%10      + 48;         // Extract ones digit
  text[9] = 176;

  // Print temperature on TFT
  TFT_Set_Font(&tahoma29x29_Bold, CL_RED, FO_HORIZONTAL);
  TFT_Write_Text(text, 85, 100);
}

void main() {
  TFT_Set_Default_Mode();
  DrawScr();

  TFT_Set_Font(&tahoma29x29_Bold, CL_BLACK, FO_HORIZONTAL);
  TFT_Write_Text("Temperature:  ", 75, 65);
  GPIO_Digital_Input(&GPIO_PORTD, _GPIO_PINMASK_ALL);     // all pins on PD is digital input

  // Main loop
  do {
    // Perform temperature reading
    Ow_Reset(&GPIO_PORTD_AHB_DATA, 4);                         // Onewire reset signal
    Ow_Write(&GPIO_PORTD_AHB_DATA, 4, 0xCC);                   // Issue command SKIP_ROM
    Ow_Write(&GPIO_PORTD_AHB_DATA, 4, 0x44);                   // Issue command CONVERT_T
    
    Delay_ms(750);

    Ow_Reset(&GPIO_PORTD_AHB_DATA, 4);
    Ow_Write(&GPIO_PORTD_AHB_DATA, 4, 0xCC);                   // Issue command SKIP_ROM
    Ow_Write(&GPIO_PORTD_AHB_DATA, 4, 0xBE);                   // Issue command READ_SCRATCHPAD
    
    temp =  Ow_Read(&GPIO_PORTD_AHB_DATA, 4);
    temp = (Ow_Read(&GPIO_PORTD_AHB_DATA, 4) << 8) + temp;
    
    // Format and display result on TFT
    Display_Temperature(temp);
    Delay_ms(1000);

  } while (1);
}

can somebody advice?
regards

 

[ucanel]

Test the code step by step.
Firstly DS18b20 can give us the temperarure 9 to 12 bits,
you selected 12 bits in these code lines

//  Set TEMP_RESOLUTION to the corresponding resolution of used DS18x20 sensor:
//  18S20: 9  (default setting; can be 9,10,11,or 12)
//  18B20: 12

const unsigned short TEMP_RESOLUTION = 12;

so you can start your test with sending temperature value
to the value converting and displaying algorithm by hand,
for example in the main loop only write these lines;

    // Format and display result on TFT
   for(temp=0; temp<= binary 0000 1111 1111 1111 ; temp+100)
{
    Display_Temperature(temp);
    Delay_ms(100);
 }

so you can check if converting and displaying algoritm works alright or not.

Then you will check other parts of the algorithm likewise.