# step by step guide

__start with [ArduinoOTA basic example](https://github.com/esp8266/Arduino/blob/master/libraries/ArduinoOTA/examples/BasicOTA/BasicOTA.ino)__

```cpp
void setup() {
  WiFi.mode(WIFI_STA);
  WiFi.begin(ssid, password);
  while (WiFi.waitForConnectResult() != WL_CONNECTED) {
    delay(5000);
    ESP.restart();  /* reload application */
  }

  /* register callbacks for OTA events */
  ArduinoOTA.onStart([]() { /* ... */ });
  ArduinoOTA.onEnd  ([]() { /* ... */ });
  ArduinoOTA.onError([](ota_error_t error) { /* ... */ });

  /* setup OTA for listening on default UDP-port 8266 */
  ArduinoOTA.begin();
}

void loop() {
  /* check for incoming OTA update */
  ArduinoOTA.handle();
}
```
___

__open serial port to esp8266 and reset__

```bash
# example output after reset
ets Jan  8 2013,rst cause:2, boot mode:(3,7)

# load binary
load 0x4010f000, len 3460, room 16
tail 4
chksum 0xcc
load 0x3fff20b8, len 40, room 4
tail 4
chksum 0xc9
csum 0xc9
v00040b70
~ld
```
___

__Boot Messages and Modes, see also [detailed documentation](https://github.com/esp8266/Arduino/blob/master/doc/boards.rst)__

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

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

```
boot mode:(x,y)
```

| x        | GPIO15   | GPIO0   | GPIO2   | Mode        |
|----------|----------|---------|---------|-------------|
| 1        | 0V       | 0V      | 3.3V    | Uart        |
| 3        | 0V       | 3.3V    | 3.3V    | Flash       |

__note:__ __y__ represents the position of the boot file

___

__modify__ _platformio.ini_

```ini
; example platformio.ini
[env:esp01_1m]
platform = espressif8266
board = esp01_1m
framework = arduino

upload_port = COM6
monitor_speed = 74880
```

___

__upload compiled binary via uart__

__note__: close serial port

```bash
$ pio run -t upload
# or use upload button in vscode
```

__open serial port to esp8266 and check Wi-Fi connection__

```bash
# monitor output:
Ready
IP address: # your local IP #
```
__modify platformio.ini accordingly__
```ini
; new platformio.ini for OTA
[env:esp01_1m]
platform = espressif8266
board = esp01_1m
framework = arduino

upload_protocol = espota
upload_port = # your local IP #
monitor_speed = 74880
```
___

__now you can upload new binaries via OTA__

```bash
$ pio run -t upload
# or use upload button in vscode
```

__what`s happening can be observed with [debug_ser.py](debug_ser.py), _PySerial_ needed !__

```bash
$ python3 debug_ser.py

# serial output:
[OTA] Start updating sketch
[OTA] Progress: 100%
[OTA] End

ets Jan  8 2013,rst cause:2, boot mode:(3,7)

load 0x4010f000, len 3460, room 16
tail 4
chksum 0xcc
load 0x3fff20b8, len 40, room 4 
tail 4
chksum 0xc9
csum 0xc9
v0004e770
@cp:B0 # copying new binary into boot flash region
ld

[Program] Booting
[Program] OTA and HTTPServer ready !
[Program] IP address: 192.168.10.108
```

___

__Process of updating__

![ota flash layout](ota_flash.png)