# 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 |
## Init sequence
The following list contains the callback init sequence
CFG: Loaded from flash at FB, Count 1581
xdrv - FUNC_SETTINGS_OVERRIDE
xdrv - FUNC_PIN_STATE
xsns - FUNC_PIN_STATE
xdrv - FUNC_MODULE_INIT
xlgt - FUNC_MODULE_INIT
xdrv - FUNC_PRE_INIT
xnrg - FUNC_PRE_INIT
SRC: Restart
xdrv - FUNC_SET_POWER
xlgt - FUNC_SET_CHANNELS
xdrv - FUNC_SET_DEVICE_POWER
Project tasmota Wemos 2 Version 7.0.0.3(tasmota)-STAGE
xdrv - FUNC_INIT
xsns - FUNC_INIT
I2C: ADS1115 found at 0x48
xdrv - FUNC_LOOP
xsns - FUNC_LOOP
xdrv - FUNC_EVERY_50_MSECOND
xlgt - FUNC_SET_CHANNELS
xsns - FUNC_EVERY_50_MSECOND
xdrv - FUNC_EVERY_100_MSECOND
xsns - FUNC_EVERY_100_MSECOND
xdrv - FUNC_EVERY_250_MSECOND
xsns - FUNC_EVERY_250_MSECOND
xdrv - FUNC_EVERY_SECOND
xsns - FUNC_EVERY_SECOND
WIF: Attempting connection...
WIF: Network (re)scan started...
WIF: Attempting connection...
WIF: Attempting connection...
WIF: Attempting connection...
WIF: Network 0, AP1, SSId indebuurt1, Channel 1, BSSId 24:D3:F2:97:C0:A1, RSSI -86, Encryption 1
WIF: Network 1, AP2, SSId indebuurt2, Channel 5, BSSId A0:AB:1B:7D:42:AC, RSSI -42, Encryption 1
WIF: Network 2, AP-, SSId indebuurt3, Channel 12, BSSId 60:E3:27:58:77:E6, RSSI -84, Encryption 1
WIF: Connecting to AP2 indebuurt2 in mode 11N as wemos2...
WIF: Attempting connection...
WIF: Attempting connection...
WIF: Attempting connection...
WIF: Connected
xdrv - FUNC_WEB_ADD_HANDLER
xsns - FUNC_WEB_ADD_HANDLER
HTP: Web server active on wemos2 with IP address 192.168.2.191
NTP: Drift 0, (UTC) Wed Nov 06 13:57:08 2019, (DST) Sun Mar 31 02:00:00 2019, (STD) Sun Oct 27 03:00:00 2019
APP: Boot Count 500
MQT: Attempting connection...
MQT: Connected
MQT: tele/wemos2/LWT = Online (retained)
MQT: cmnd/wemos2/POWER =
MQT: Subscribe to cmnd/wemos2/#
MQT: Subscribe to cmnd/sonoffs/#
MQT: Subscribe to cmnd/DVES_15568C_fb/#
xdrv - FUNC_MQTT_SUBSCRIBE
MQT: tele/wemos2/INFO1 = {"Module":"Generic","Version":"7.0.0.3(tasmota)","FallbackTopic":"cmnd/DVES_15568C_fb/","GroupTopic":"cmnd/sonoffs/"}
MQT: tele/wemos2/INFO2 = {"WebServerMode":"Admin","Hostname":"wemos2","IPAddress":"192.168.2.191"}
MQT: tele/wemos2/INFO3 = {"RestartReason":"Software/System restart"}
MQT: stat/wemos2/RESULT = {"POWER1":"OFF"}
MQT: stat/wemos2/POWER1 = OFF
MQT: stat/wemos2/RESULT = {"POWER2":"ON"}
MQT: stat/wemos2/POWER2 = ON
xdrv - FUNC_MQTT_INIT
CFG: Saved to flash at FA, Count 1582, Bytes 4096