From: tnp@invalid.invalid   
      
   On 29/03/2025 13:34, The Natural Philosopher wrote:   
   >   
   > I have a PI PICO W which I am developing code for amongst which is a   
   > TMP36 temperature sensor   
   > The code I have reused form other thermostat projects but its suddenly   
   > giving the odd false reading.   
   >   
   > #define CHIP_TEMP_IO 28   
   > #define CHIP_ADC 2   
   > #define RELAY_IO 21   
   > #define IN 0   
   > #define OUT 1   
   > #define ON 1   
   > #define OFF 0   
   >   
   > void initialise_hardware()   
   >      {   
   >      adc_init();   
   >      adc_gpio_init(CHIP_TEMP_IO);   
   >      gpio_init(RELAY_IO);   
   >      gpio_set_dir(RELAY_IO,OUT);   
   >      }   
   > void set_relay(int flag)   
   >      {   
   >      cyw43_arch_gpio_put(CYW43_WL_GPIO_LED_PIN, flag); // set the lamp   
   >      gpio_put(RELAY_IO,flag);    //set the relay   
   >      }   
   > float read_temperature()   
   >      {   
   >      static int index;   
   >      static int flag;  //initialised to zero at startup   
   >      static uint32_t rawbuf[32];   
   >      const float conversion_factor = 3.3f / (1<<12);   
   >      float result;   
   >      float last;   
   >      int i;   
   >      uint32_t raw;   
   >      adc_select_input(CHIP_ADC);   
   >      raw = adc_read();   
   > //wtf?   
   >      printf ("Raw=%0X\n",raw);   
   >   
   >      result=((float)raw)*conversion_factor;   
   >   
   >      return (100*result-54);   // the pcb warms them up by about 4   
   degrees   
   >      }   
   >   
   > I am reading the temperature every two seconds as in   
   >      while (1)   
   >          {   
   >          sleep_ms(2000);   
   >          flag=(flag? OFF:ON);   
   >          set_relay(flag);   
   >          temperature = read_temperature();   
   >          printf("Temperature is %.1f C\n",temperature);   
   >          }   
   >   
   > about one time in ten the output jumps to about 20°C less than expected   
   > e.g.   
   >   
   >   
   > Raw=3BE   
   > Temperature is 23.2 C   
   > Raw=3BE   
   > Temperature is 23.2 C   
   > Raw=3BE   
   > Temperature is 23.2 C   
   > Raw=29B   
   > Temperature is -0.3 C /************************   
   > Raw=3C0   
   > Temperature is 23.3 C   
   > Raw=3C0   
   > Temperature is 23.3 C   
   > Raw=3BF   
   > Temperature is 23.3 C   
   > Raw=3BF   
   > Temperature is 23.3 C   
   > Raw=3BF   
   > Temperature is 23.3 C   
   > Raw=3C1   
   >   
   >   
   > I have added decoupling to the TMP36 supply which is fed from the ADC   
   > 3.3v supply which seems to be a steady 3.29V according to my DVM.   
   >   
   > Do I have a bad PICO W? TMP 36 or what?   
   >   
   > Other PICOs with the same chip don't do this...   
   > The only difference is that this PICO is running different and a lot   
   > more wifi/server code   
   > Is it possible that some interrupt is - er - interrupting the ADC read   
   > with dire results?   
   >   
   >   
   >   
   > I cannot but think this is a hardware issue.   
   I found another TMP36 from an old project and switched it in.   
   No joy.   
   Looks like its PI related   
      
   “it should be clear by now to everyone that activist environmentalism   
   (or environmental activism) is becoming a general ideology about humans,   
   about their freedom, about the relationship between the individual and   
   the state, and about the manipulation of people under the guise of a   
   'noble' idea. It is not an honest pursuit of 'sustainable development,'   
   a matter of elementary environmental protection, or a search for   
   rational mechanisms designed to achieve a healthy environment. Yet   
   things do occur that make you shake your head and remind yourself that   
   you live neither in Joseph Stalin’s Communist era, nor in the Orwellian   
   utopia of 1984.”   
      
   Vaclav Klaus   
      
   --- SoupGate-DOS v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)