Attiny85: Default de fábrica e bricando para testes de reset via HVSP

Sem querer, eu já bricava um attiny. Propositalmente então, deve ser moleza. Mas primeiro, anotar quais são as configurações de fábricas e constatar no microcontrolador, é uma obrigação.

No site http://www.engbedded.com/fusecalc podemos calcular e ver os padrões de fábrica dos microcontroladores AVR. Os fuses do Attiny85 estão motrados assim para a configuração default

Ext. Clock; Start-up time PWRDWN/RESET: 6 CK/14 CK + 0 ms;   [CKSEL=0000 SUT=00] Ext. Clock; Start-up time PWRDWN/RESET: 6 CK/14 CK + 4.1 ms; [CKSEL=0000 SUT=01] Ext. Clock; Start-up time PWRDWN/RESET: 6 CK/14 CK + 65 ms;  [CKSEL=0000 SUT=10] PLL Clock; Start-up time PWRDWN/RESET: 1K CK/14 CK + 4 ms; [CKSEL=0001 SUT=00] PLL Clock; Start-up time PWRDWN/RESET: 16K CK/14 CK + 4 ms; [CKSEL=0001 SUT=01] PLL Clock; Start-up time PWRDWN/RESET: 1K CK/14 CK + 64 ms; [CKSEL=0001 SUT=10] PLL Clock; Start-up time PWRDWN/RESET: 16K CK/14 CK + 64 ms; [CKSEL=0001 SUT=11] Int. RC Osc. 8 MHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 0 ms; [CKSEL=0010 SUT=00] Int. RC Osc. 8 MHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 4 ms; [CKSEL=0010 SUT=01] Int. RC Osc. 8 MHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 64 ms; [CKSEL=0010 SUT=10]; default value Int. RC Osc. 6.4 MHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 64 ms; [CKSEL=0011 SUT=00] Int. RC Osc. 6.4 MHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 64 ms; [CKSEL=0011 SUT=01] Int. RC Osc. 6.4 MHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 4 ms; [CKSEL=0011 SUT=10] Int. RC Osc. 6.4 MHz; Start-up time PWRDWN/RESET: 1 CK/14 CK + 0 ms; [CKSEL=0011 SUT=11] WD. Osc. 128 kHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 0 ms; [CKSEL=0100 SUT=00] WD. Osc. 128 kHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 4 ms; [CKSEL=0100 SUT=01] WD. Osc. 128 kHz; Start-up time PWRDWN/RESET: 6 CK/14 CK + 64 ms; [CKSEL=0100 SUT=10] Ext. Low-Freq. Crystal; Start-up time PWRDWN/RESET: 1K CK/14 CK + 0 ms; [CKSEL=0110 SUT=00]  Ext. Low-Freq. Crystal; Start-up time PWRDWN/RESET: 1K CK/14 CK + 4 ms; [CKSEL=0110 SUT=01]  Ext. Low-Freq. Crystal; Start-up time PWRDWN/RESET: 32K CK/14 CK + 64 ms; [CKSEL=0110 SUT=10]  Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 4.1 ms; [CKSEL=1000 SUT=00]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 65 ms;  [CKSEL=1000 SUT=01]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 0 ms;   [CKSEL=1000 SUT=10]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 4.1 ms; [CKSEL=1000 SUT=11]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 65 ms;  [CKSEL=1001 SUT=00]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 0 ms;   [CKSEL=1001 SUT=01]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 4.1 ms; [CKSEL=1001 SUT=10]    Ext. Crystal Osc.; Frequency 0.4-0.9 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 65 ms;  [CKSEL=1001 SUT=11]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 4.1 ms; [CKSEL=1010 SUT=00]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 65 ms;  [CKSEL=1010 SUT=01]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 0 ms;   [CKSEL=1010 SUT=10]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 4.1 ms; [CKSEL=1010 SUT=11]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 65 ms;  [CKSEL=1011 SUT=00]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 0 ms;   [CKSEL=1011 SUT=01]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 4.1 ms; [CKSEL=1011 SUT=10]    Ext. Crystal Osc.; Frequency 0.9-3.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 65 ms;  [CKSEL=1011 SUT=11]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 4.1 ms; [CKSEL=1100 SUT=00]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 65 ms;  [CKSEL=1100 SUT=01]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 0 ms;   [CKSEL=1100 SUT=10]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 4.1 ms; [CKSEL=1100 SUT=11]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 65 ms;  [CKSEL=1101 SUT=00]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 0 ms;   [CKSEL=1101 SUT=01]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 4.1 ms; [CKSEL=1101 SUT=10]    Ext. Crystal Osc.; Frequency 3.0-8.0 MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 65 ms;  [CKSEL=1101 SUT=11]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 4.1 ms; [CKSEL=1110 SUT=00]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 258 CK/14 CK + 65 ms;  [CKSEL=1110 SUT=01]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 0 ms;   [CKSEL=1110 SUT=10]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 4.1 ms; [CKSEL=1110 SUT=11]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 1K CK /14 CK + 65 ms;  [CKSEL=1111 SUT=00]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 0 ms;   [CKSEL=1111 SUT=01]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 4.1 ms; [CKSEL=1111 SUT=10]    Ext. Crystal Osc.; Frequency 8.0-    MHz; Start-up time PWRDWN/RESET: 16K CK/14 CK + 65 ms;  [CKSEL=1111 SUT=11]

Low	High	Extended	Action	AVRDUDE arguments
0x	0x	0x*	Apply manual changes to the values on the left side, or load factory default values for the selected device.	-U lfuse:w:0x62:m -U hfuse:w:0xdf:m -U efuse:w:0xff:m Select (try triple-click) and copy-and-paste this option string into your avrdude command line. You may specify multiple -U arguments within one call of avrdude. * Note that some numerical values refer to fuses containing undefined bits (set to '1' here). Depending on the target device these fuse bits will be read either as '0' or '1'. Verification errors will occur if the values are read back with undefined bits set to '0'. Everything is fine if the values read from the device are either the same as programmed, or the following values (undefined set to '0'):Extended: 0x01.

Meu Attiny85 recém resetado mostra as informações abaixo, no AVRDUDESS:

Isto é, as informações batem.

Para bricar o Attiny85: o meio mais fácil que achei foi configurar o Low para 0x00 no AVRDUDESS e dar um write. Observe a mensagem do console depois de dar um Detect:

Depois disso, pode tentar gravar os fuses de fábrica ou qualquer outro, que o AVRDUDESS não vai mais conseguir ler ou gravar qualquer informação.

Passando pelo circuito de reset via HVSP, o resultado é esse, no serial monitor da IDE:

Voltando ao AVRDUDESS, o Detect dá a tela:

Repeti duas vezes, o microcontrolador bricou as duas vezes e ressucitou duas vezes. 

Realmente, apesar de simplificado, o circuito resetador funciona mesmo e o mais importante: é muito fácil de montar.