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Merge pull request #1018 from Links2004/docu

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add documentation about boot messages and mode meaning
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Markus 2015-11-14 17:28:26 +01:00
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doc/boards.md
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@ -162,3 +162,54 @@ 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)
```
note:
- GPIO2 is used as TX output and the internal Pullup is enabled on boot.
#### 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 | 3.3V | 0V | SDIO |
| 7 | 3.3V | 3.3V | 3.3V | SDIO |
note:
- number = ((GPIO15 << 2) | (GPIO0 << 1) | GPIO2);