8000 add documentation about boot messages and mode meaning by Links2004 · Pull Request #1018 · esp8266/Arduino · GitHub
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add documentation about boot messages and mode meaning #1018

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Nov 14, 2015
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add documentation about boot messages and mode meaning #1018

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9db6504
add documentation about boot messages and mode meaning
Links2004 Nov 14, 2015
5192ddb
add node about TX on GPIO2
Links2004 Nov 14, 2015
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add documentation about boot messages and mode meaning
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@Links2004
Links2004 committed Nov 14, 2015
commit 9db650482cc255e4d49fb3e9a8bf6ad0a5fdc900
49 changes: 49 additions & 0 deletions doc/boards.md
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Expand Up @@ -162,3 +162,52 @@ ESPxx Hardware

### Improved Stability
![ESP improved stability](ESP_improved_stability.png)

### Boot Messages and Modes

The ESP module checks at every boot the Pins 0, 2 and 15.
based on them its boots in different modes:

| GPIO15 | GPIO0 | GPIO2 | Mode |
| ------ | ----- | ----- | -------------------------------- |
| 0V | 0V | 3.3V | Uart Bootloader |
| 0V | 3.3V | 3.3V | Boot sketch (SPI flash) |
| 3.3V | x | x | SDIO mode (not used for Arduino) |


at startup the ESP prints out the current boot mode example:
```
rst cause:2, boot mode:(3,6)
```

#### rst cause

| Number | Description |
| ------ | ---------------------- |
| 0 | unknown |
| 1 | normal boot |
| 2 | reset pin |
| 3 | software reset |
| 4 | watchdog reset |


#### boot mode

the first value respects the pin setup of the Pins 0, 2 and 15.

| Number | GPIO15 | GPIO0 | GPIO2 | Mode |
| ------ | ------ | ----- | ----- | ---------- |
| 0 | 0V | 0V | 0V | Not valid |
| 1 | 0V | 0V | 3.3V | Uart |
| 2 | 0V | 3.3V | 0V | Not valid |
| 3 | 0V | 3.3V | 3.3V | Flash |
| 4 | 3.3V | 0V | 0V | SDIO |
| 5 | 3.3V | 0V | 3.3V | SDIO |
| 6 | 3.3V | 47A3 3.3V | 0V | SDIO |
| 7 | 3.3V | 3.3V | 3.3V | SDIO |

Note:

number = ((GPIO15 << 2) | (GPIO0 << 1) | GPIO2);


0