Flashing Atmega328PB only works once

pert · April 30, 2018, 9:42pm

Glad to hear MiniCore is working for you!

I did a comparison between the MiniCore bootloader source and the watterott source you pointed out. There are some differences in the handling of MCUSR but also watterott's has so auto baud rate detection code added:

github.com

MCUdude/optiboot_flash/blob/master/optiboot_flash.c#L508-L536


      
          
          

          
  /*
             * Protect as much from MCUSR as possible for application
             * and still skip bootloader if not necessary
             *
             * Code by MarkG55
             * see discusion in https://github.com/Optiboot/optiboot/issues/97
             */
          
          
// Fix ATmega128 avr-libc bug
          #if defined(__AVR_ATmega128__)
          	ch = MCUCSR;
          #else
          	ch = MCUSR;
          #endif
          
          
// This is necessary on targets that where the CLKPR has been set in user application
          #if defined(CLKPR) && F_CPU != 1000000L
            CLKPR = 0x80; // Enable the clock prescaler

This file has been truncated. show original

vs

github.com

watterott/Wattuino/blob/master/software/Optiboot/optiboot.c#L493-L498


      
            MCUSR = 0;
          #else
            ch = MCUCSR;
            MCUCSR = 0;
          #endif
            if (ch & (_BV(WDRF) | _BV(BORF) | _BV(PORF)))

I believe the purpose of the added code in the MiniCore version was to preserve the contents of the MCUSR register so that information can be used in the application.

Another significant difference I notice is that the watterott bootloader has auto baudrate detection:

github.com

watterott/Wattuino/blob/master/software/Optiboot/optiboot.c#L539-L572


      
          //Auto Baud Rate Detection
          //first byte is STK_GET_SYNC (0x30 = 0b00110000)
          //get bit time
          TCNT1H = 0;
          TCNT1L = 0;
          while(UART_PIN & _BV(UART_RX_BIT)); //wait for start bit
          while(!(UART_PIN & _BV(UART_RX_BIT))); //wait till over (start bit + 4 low data bits)
          TCCR1B = _BV(CS10); //start timer clk=F_CPU/1
          while(UART_PIN & _BV(UART_RX_BIT)); //wait till over (2 high data bits)
          TCCR1B = 0; //stop timer
          //calc UBRR value
          typedef union{
            struct{
              uint8_t l;
              uint8_t h;
            } u8;
            uint16_t u16;
          }timer_data;
          timer_data td;
          td.u8.l = TCNT1L;

This file has been truncated. show original

Topic		Replies	Views
Can an MCU be partly bad? 3rd Party Boards	29	13328	May 6, 2021
Sketches Only Upload Once IDE 1.x	11	3387	May 5, 2021
Uploading sketch on ATMEGA328PB 3rd Party Boards	19	16784	May 6, 2021
Uploading sketch to atmega328P 3rd Party Boards	19	8234	May 6, 2021
[solved] atmega328p not working as expected IDE 1.x	3	670	May 5, 2021

Flashing Atmega328PB only works once

Related topics