0

The board has components connected the MCU. Is it possible to re-program the MCU if we can take only the required connection out without removing the IC itself? Will the components connected to the pins hinder the reprogramming of the MCU? The components are three LED push buttons, an I2C OLED display, and a buzzer.

ocrdu
  • 8,705
  • 21
  • 30
  • 42
Abhijith CB
  • 13
  • 2
  • 1
    It depends what there is on each programming pin and if the programming adapter can freely use those pins tor programming. And the programning must still be allowed on the MCU, so if it is already running in a device, it might be locked so you can't reprogram the MCU even if you take it off from the board. So there is not enough info to answer your question. – Justme Mar 05 '23 at 09:30
  • That things are called ICSP, in- circuit serial programming. If MCU has the options it could be done. But some changes may be needed on PCB because some elements on board can interfere with programming signals. – user263983 Mar 05 '23 at 14:01

1 Answers1

1

It depends on what is connected to each of the ISP pins. You generally want what ever is also connected to those pins to be high impedance and low capacitance so they do not interfere with programming signals. It also a good idea to not have those pins controlling anything that you would not want to be inadvertently activated during programming (i.e. accelerator of a car).

Buttons are OK as long as the button is no closed (a short).

LEDs can be OK if they have current limiting resistors on them, although they may blink during programming.

The display and buzzer are also probably OK, but again they might do stuff during programming.

This application note describes the requirements in more detail...

http://ww1.microchip.com/downloads/en/appnotes/atmel-0943-in-system-programming_applicationnote_avr910.pdf

bigjosh
  • 9,888
  • 29
  • 48
  • The points you have noted here are great, though you should specify that these are only relevant for MISO, MOSI and SCK pins. The thing to REALLY watch out for is the Reset pin on the ATTiny85, which has very special requirements, and often trips up reprogramming. Oh wait .. you HAVE mentioned ISP pins only. Sorry - didn't catch that. – Kripacharys Mar 06 '23 at 07:26