mirror of https://github.com/ARMmbed/mbed-os.git
101 lines
4.3 KiB
Markdown
101 lines
4.3 KiB
Markdown
# ESP8266 WiFi driver for Mbed OS
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The Mbed OS driver for the ESP8266 WiFi module.
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## Firmware version
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ESP8266 modules come in different shapes and formats, but the firmware version is the most important factor. To
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make sure that the firmware in your module is compatible with Mbed OS, follow the
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[Update guide](https://developer.mbed.org/teams/ESP8266/wiki/Firmware-Update).
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This driver supports AT firmware versions 1.3.0 to 1.7.0. We advise updating the
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[AT firmware](https://www.espressif.com/en/support/download/at?keys=) to at least version 1.7.0.
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## Restrictions
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* The ESP8266 Wi-Fi module does not allow the TCP client to bind to a specific port.
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* Setting up a UDP server is not possible.
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* The serial port does not have hardware flow control enabled by default. Additionally, the AT command set does not have a method for limiting the download rate. Therefore, downloading anything larger than the serial port input buffer is unreliable
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unless you use [AT firmware](https://www.espressif.com/en/support/download/at?keys=) version 1.7.0 or later. With older
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firmware, an application should be able to read fast enough to stay ahead of the network. This applies mostly to TCP
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protocol, where data would be lost without notification. On UDP using all firmware versions, the higher-layer protocol should recover from packet loss.
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## Mandatory configuration
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 configuration assumes Arduino form factor. Please adjust according to your board. You can override parameters from your app config file.
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At minimum, check the following configuration parameters:
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```javascript
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{
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"name": "esp8266",
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"config": {
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"tx": {
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"help": "TX pin for serial connection",
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"value": null <- 'D1' by default if Arduino, adjust based on your board
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},
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"rx": {
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"help": "RX pin for serial connection",
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"value": null <- 'D0' by default if Arduino, adjust based on your board
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},
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"provide-default": {
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"help": "Provide default WifiInterface. [true/false]",
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"value": false <- Set to 'true' if this is the interface you are using
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},
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"socket-bufsize": {
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"help": "Max socket data heap usage",
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"value": 8192 <- Without HW flow control more is better. Once the limit is reached packets are
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dropped - does not matter is it TCP or UDP.
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}
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}
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}
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```
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## UART HW flow control
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UART HW flow control requires you to additionally wire the CTS and RTS flow control pins between your board and your
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ESP8266 module. After this, remember to add the configuration option for flow control to your app configuration file. This example uses the [ST NUCLEO-F429ZI](https://os.mbed.com/platforms/ST-Nucleo-F429ZI/) board and
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[ESPBee XBee Module](https://www.cascologix.com/product/espbee/).
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**Note:** Not all modules expose ESP8266's RTS and CTS pins, so choose modules carefully.
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Once you have your hardware set up, add a configuration like the following to your app configuration file. Arduino pins D1 and D0 are used as TX and RX:
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``` javascript
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"target_overrides": {
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"NUCLEO_F429ZI": {
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"esp8266.rts": "PG_12",
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"esp8266.cts": "PG_15"
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}
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```
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### Example board pins
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* TX: D1 (Arduino Uno Revision 3 connectivity headers)
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* RX: D0 (Arduino Uno Revision 3 connectivity headers)
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* RTS: PG_12 (STMicroelectronics Morpho extension pin headers)
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* CTS: PG_15 (STMicroelectronics Morpho extension pin headers)
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### Example ESP8266 pins
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* TX: D1 (Arduino Wireless Protoshield headers)/ TX (ESPBee XBee headers)
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* RX: D0 (Arduino Wireless Protoshield headers)/ RX (ESPBee XBee headers)
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* RTS: RTS (ESPBee XBee headers)
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* CTS: CTS (ESPBee XBee headers)
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### Connections
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With these pictures only consider the green and yellow wires which are connected to ESP8266. The pink wire is for reset and
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the rest are for firmware update. TX and RX go through Arduino pins D1 and D0.
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**Note:** Pull down GPIO15(ESPBee RTS) during startup to **boot from flash**, instead of **firmware update** or
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**boot from SD card**. Once the software is running, the same pin is used as the RTS pin:
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* Board TX: ESP8266 RX
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* Board RX: ESP8266 TX
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* Board RTS (grey): ESP8266 CTS(yellow)
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* Board CTS (white): ESP8266 RTS(green)
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