# Basic API information Tasmota can easily be extended by developers using provided function pointers as callback Ids. This document lists the available callback function Ids. See the wiki (https://github.com/arendst/Tasmota/wiki/Sensor-API) for more information. Callback availability can be checked by searching for either XdrvCall, XsnsCall, XdspCall and XnrgCall. ## Driver, Sensor and Energy Callback Ids The following table lists Callback Ids and their availability for a Driver, Sensor or Energy service. Callback Id | Bool | Version | xdrv | xsns | xnrg | Description ----------------------------|------|----------|------|------|------|---------------------------------- FUNC_SETTINGS_OVERRIDE | | 6.2.1.19 | x | | | Override start-up settings FUNC_MODULE_INIT | x | 6.2.1.17 | x | | | Init module specific parameters FUNC_PRE_INIT | | | x | | x | Once GPIO have been established FUNC_INIT | | | x | x | x | At end of initialisation FUNC_LOOP | | | x | | | In main loop FUNC_EVERY_50_MSECOND | | | x | x | | FUNC_EVERY_100_MSECOND | | | x | x | | FUNC_EVERY_200_MSECOND | | | | x | x | FUNC_EVERY_250_MSECOND | | | x | | | FUNC_EVERY_SECOND | | | x | x | x | FUNC_PREP_BEFORE_TELEPERIOD | | | | x | | Deprecated. Use a FUNC_EVERY_ FUNC_JSON_APPEND | | | | x | | Extend teleperiod JSON text FUNC_WEB_APPEND | | | | x | | Extend webgui ajax info FUNC_SAVE_BEFORE_RESTART | | | | x | | Just before a planned restart FUNC_COMMAND | x | | x | x | | When a command is not recognized FUNC_COMMAND_DRIVER | x | 6.4.1.21 | x | | | When command Driver\ is executed FUNC_COMMAND_SENSOR | x | 6.4.1.21 | | x | | When command Sensor\ is executed FUNC_MQTT_SUBSCRIBE | | 5.12.0k | x | | | At end of MQTT subscriptions FUNC_MQTT_INIT | | 5.12.0k | x | | | Once at end of MQTT connection FUNC_MQTT_DATA | x | 5.12.0k | x | | | Before decoding command FUNC_SET_POWER | | | x | | | Before setting relays FUNC_SET_DEVICE_POWER | x | 6.2.1.18 | x | | | Set relay FUNC_SHOW_SENSOR | | | x | | | When FUNC_JSON_APPEND completes FUNC_RULES_PROCESS | x | 6.0.0 | x | | | Process specific rule FUNC_SERIAL | x | | x | | x | Process serial data FUNC_FREE_MEM | | | x | | | Show free memory for debugging FUNC_BUTTON_PRESSED | x | 6.2.1.18 | x | | | When a button is pressed FUNC_WEB_ADD_BUTTON | | 6.2.1.14 | x | x | | Add a Configuration Button to GUI FUNC_WEB_ADD_MAIN_BUTTON | | 6.2.1.14 | x | x | | Add a main button to GUI FUNC_WEB_ADD_HANDLER | | 6.2.1.14 | x | x | | Add a webserver handler ## Display Call back Ids The following table lists all Callback Ids for a Display service. Callback Id | Bool | Version | Description ------------------------------|------|----------|--------------------- FUNC_DISPLAY_INIT_DRIVER | | 6.1.1.7 | FUNC_DISPLAY_INIT | | 6.1.1.7 | FUNC_DISPLAY_EVERY_50_MSECOND | | 6.1.1.7 | FUNC_DISPLAY_EVERY_SECOND | | 6.1.1.7 | FUNC_DISPLAY_MODEL | x | 6.1.1.7 | FUNC_DISPLAY_MODE | | 6.1.1.7 | FUNC_DISPLAY_POWER | | 6.1.1.7 | FUNC_DISPLAY_CLEAR | | 6.1.1.7 | FUNC_DISPLAY_DRAW_FRAME | | 6.1.1.7 | FUNC_DISPLAY_DRAW_HLINE | | 6.1.1.7 | FUNC_DISPLAY_DRAW_VLINE | | 6.1.1.7 | FUNC_DISPLAY_DRAW_LINE | | 6.1.1.7 | FUNC_DISPLAY_DRAW_CIRCLE | | 6.1.1.7 | FUNC_DISPLAY_FILL_CIRCLE | | 6.1.1.7 | FUNC_DISPLAY_DRAW_RECTANGLE | | 6.1.1.7 | FUNC_DISPLAY_FILL_RECTANGLE | | 6.1.1.7 | FUNC_DISPLAY_TEXT_SIZE | | 6.1.1.7 | FUNC_DISPLAY_FONT_SIZE | | 6.1.1.7 | FUNC_DISPLAY_ROTATION | | 6.1.1.7 | FUNC_DISPLAY_DRAW_STRING | | 6.1.1.7 | FUNC_DISPLAY_ONOFF | | 6.1.1.7 |