3 ms·

Removing the battery is the same as opening the switch in this circuit: they both will indicate that the device has been tampered with (output will be low).

svnt 4y ago
I had presumed that there was only one battery for the whole system though, in which case there is nothing awake to detect its removal and the tamper circuit will reset once the battery is reconnected. I guess there is not enough context but it doesn’t seem particularly novel to me.
- walterbell 4y ago
  Would you recommend a better circuit or specific microcontroller?
  - svnt 4y ago
    Integrating with the microcontroller in low-cost settings is usually pretty specific to a given implementation. If cost isn’t a big factor and you wanted to go big on security then something like this Maxim part would do it. https://datasheets.maximintegrated.com/en/ds/MAX32558.pdf https://datasheets.maximintegrated.com/en/ds/MAX32558.pdf However if that’s overkill or you’re allergic to Maxim then searching on AVR, PIC, MSP430, Cortex M0 + tamper detect application note should get you a lot of examples. Depending on the product, microcontroller and mode of operation you might come in on a battery monitor input, a more robust but “digital” external interrupt, a comparator, just an ADC, or something else. Even creative use of built-in voltage regulation can sometimes work. If you wanted to know if the battery was removed you have simple options like cap up your supply, rapidly switch power modes, save off a bit somewhere before BOD kicks in. Alternatively in some cases you could just use the BOD if your hardware is set up correct. The linked circuit is fine as a jelly-bean circuit in low volume/low security products and allows you to tick the “tamper detection” box on the cut sheet.

3 ms·

Removing the battery is the same as opening the switch in this circuit: they both will indicate that the device has been tampered with (output will be low).

by jhallenworld 4y ago

svnt 4y ago
I had presumed that there was only one battery for the whole system though, in which case there is nothing awake to detect its removal and the tamper circuit will reset once the battery is reconnected. I guess there is not enough context but it doesn’t seem particularly novel to me.
- walterbell 4y ago
  Would you recommend a better circuit or specific microcontroller?
  - svnt 4y ago
    Integrating with the microcontroller in low-cost settings is usually pretty specific to a given implementation. If cost isn’t a big factor and you wanted to go big on security then something like this Maxim part would do it. https://datasheets.maximintegrated.com/en/ds/MAX32558.pdf https://datasheets.maximintegrated.com/en/ds/MAX32558.pdf However if that’s overkill or you’re allergic to Maxim then searching on AVR, PIC, MSP430, Cortex M0 + tamper detect application note should get you a lot of examples. Depending on the product, microcontroller and mode of operation you might come in on a battery monitor input, a more robust but “digital” external interrupt, a comparator, just an ADC, or something else. Even creative use of built-in voltage regulation can sometimes work. If you wanted to know if the battery was removed you have simple options like cap up your supply, rapidly switch power modes, save off a bit somewhere before BOD kicks in. Alternatively in some cases you could just use the BOD if your hardware is set up correct. The linked circuit is fine as a jelly-bean circuit in low volume/low security products and allows you to tick the “tamper detection” box on the cut sheet.