Blank display if S1820 probe enabled

Mbed OS
,
1

I am new to mbed. I started by importing the lcddemo for my 746g-disco board.
The lcd demo builds fine and display works.

After adding DS1820 libraries, if I add the line: DS1820 probe(PI_2); the display is blank.
Comment out this line and the text is displayed.

#include "mbed.h"
#include "stm32746g_discovery_lcd.h"
#include "DS1820.h"
DS1820 probe(PI_2);
2

Hi there,

It looks like the code is stuck in the constructor or something similar.
Can you share a link to an example program or library of the DS1820 what you use?
Did you check the serial output of the crash report?

BR, Jan

3

of course, now published at

4

When you read the serial output of the board, you will see this crash

++ MbedOS Error Info ++
Error Status: 0x80FF0100 Code: 256 Module: 255
Error Message: Fatal Run-time error
Location: 0x8005BCF
Error Value: 0x0
For more info, visit: mbedos-error
– MbedOS Error Info –
No unassigned DS1820 found!

The last line is the reason and a rootcause is probably a bad timing or pins setting.

  • When you check the pull-requests of that lib, you will found, for example this one, which is already fixed.
  • Second option is change the DS1820 lib to this DS1820 library , which also has better support by owner for now.

BR, Jan

1 Like
5

Still no display with the new DS1820 library.

I added the swo lib to add some debug printing. Now I can see the programs keeps running and is printing messages in the swv console. With no sensors connected yet I see the line saying so being printed in the swv.
Then I see the expected “start display” line being spit out. So far everything is ok.
But still no display.

To get the display working I have to comment out the Enumerating sensors code.
I get a strong feeling the onewire lib is conflicting with the lcd hardware.

6

I can confirm abnormal reaction. I made an investigation and code bellow is working but I have no Idea what is the reason.

#include "mbed.h"
#include "stm32746g_discovery_lcd.h"
#include "DS1820.h"

#define     SENSORS_COUNT   64

OneWire     oneWire(D8);
DS1820*     ds1820[SENSORS_COUNT];
int         sensors_found;      // counts the actually found DS1820 sensors
float       temp = 0;
int         result = 0;

int main()
{
    printf("Starting\n");

    for(sensors_found = 0; sensors_found < SENSORS_COUNT; sensors_found++) {
        ds1820[sensors_found] = new DS1820(&oneWire);
        if(!ds1820[sensors_found]->begin()) {
            delete ds1820[sensors_found];
            break;
        }
    }
    
    if (sensors_found == 0) {
        printf("No DS1820 sensor found!\r\n");
    } else {
        printf("Found %d sensors.\r\n", sensors_found);
        printf("-------------------\r\n");
        HAL_Delay(500);
        char buffer[20]= {0};
       
        BSP_LCD_Init();
        BSP_LCD_LayerDefaultInit(LTDC_ACTIVE_LAYER, LCD_FB_START_ADDRESS);
        BSP_LCD_SelectLayer(LTDC_ACTIVE_LAYER);
        BSP_LCD_SetFont(&LCD_DEFAULT_FONT);
        BSP_LCD_Clear(LCD_COLOR_PETROL);
        BSP_LCD_SetBackColor(LCD_COLOR_PETROL);
        BSP_LCD_SetTextColor(LCD_COLOR_WHITE);
        BSP_LCD_DisplayStringAt(0, 1, (uint8_t *)"MBED Robin", CENTER_MODE);
        BSP_LCD_SetTextColor(LCD_COLOR_YELLOW);
        BSP_LCD_DisplayStringAt(0, 100, (uint8_t *)"DISCOVERY STM32F746NG", CENTER_MODE);

       
        while(1) {    
            for(int i = 0; i < sensors_found; i++) {
                ds1820[i]->startConversion();      // start temperature conversion from analog to digital
                HAL_Delay(500); // let DS1820s complete the temperature conversion
                if(ds1820[i]->isPresent()){
                    temp = ds1820[i]->read();
                    //printf("temp[%d] = %3.1f%cC\n", i, ds1820[i]->read(), 176); 
                    sprintf (buffer, "temp[%d] = %3.1fC", i, ds1820[i]->read());
                    BSP_LCD_DisplayStringAt(20, 175, (uint8_t *)buffer, LEFT_MODE);  
                } 
            }  
        }
    }
}

When I tried some changes of this, the display show nothing or the screen slowly disappear with a noise.

  • For some reason it is necessary to use HAL_Delay(ms); instead of wait(s); or for the current version of Mbed thread_sleep_for(ms);
  • When you place an oneWire communication between the Init() + first setting of the display and the while loop, also it will not working and so on.
  • I checked the pin map and it looks like these pins (A0, A1, D8, D12) are free.

BR, Jan

7

You are probably right in that wait_ms is not compatible with mbed threading.
And I know I will need parralleel treads for my final project.
So I replaced all ‘wait_ms()’ for thread_sleep_for(ms) in ds1820.ccp
Also replaced the HAL_Delay in main. Better keep with one system.

I added rendering the display once before the sensor enumeration also, just to see what happens.
Still no display though.

But look at the output in my SWV:

2020-04-15_15-19-02

These output errors are rare, but the do exist.
Maybe be something going wrong with timing are thread scheduling?

By the way, while I had the situation where the displayed image slowly turns into noise,
Most of the builds, including this latest one, the display is simply blank.

At this moment I am moving from the online compiler to PlatformIO in Visual Code.
In parallel I will create a project here using the MaximInterface libary, to see how that turns out.

8

It seems the problem is not any DS1820 library but about the BSP library is not friendly with Mbed’s delay functions/methods (thread_sleep_for(ms); ThisThread::sleep_for(ms);) and the HAL_Delay(ms); must be used. Maybe someone clever could explain this to us.
However you can try to import this example DISCO-F746NG_OneWire .

BR, Jan