Important

This is a release candidate. It is intended for testing, and some things still need fixing and fine tuning. Please use it with caution and report back any issues at https://github.com/cleanflight/cleanflight/issues. Thank you.

Important information when upgrading

• Cleanflight 4.2 brings some changes to how targets are downloaded and installed. The latest release of Cleanflight Configurator, 2.6.0, contains the changes necessary to support this. For this reason it is important that you update to the version 2.6.0 or newer of Cleanflight Configurator (installation instructions here) in order to get the latest version of your targets installed;
• if you are using the Blackbox Explorer, there will be an updated version 3.5.0 to go with Cleanflight 4.2 (installation instructions here);
• version 1.5.0 of the Cleanflight TX lua scripts will be released soon. This includes changes to go with Cleanflight 4.2 (installation instructions here);
• please do not paste tuning configurations from previous versions of the firmware. Some defaults have been changed, and some parameters are used in different ways, so previous tuning settings will not work well with Cleanflight 4.1;
• after installing new firmware or resetting the configuration, the motor output protocol selected by default is now 'disabled'. This means that the correct motor protocol has to be selected before the craft can be armed. But this also removed the limitation on the maximum possible PID loop speed imposed by the pre-selected legacy protocol (OneShot125) in earlier versions, resulting in the maximum possible PID loop speed for each MCU type being pre-selected. Arming will be disabled and a warning displayed in configurator until a motor output protocol has been selected;
• when enabling bidirectional Dshot, the maximum possible PID loop speed for Dshot protocols will be reduced by half to accommodate for the time taken by the ESC to send the RPM data packet to the flight controller. In particular, this means that with Dshot300 and bidirectional Dshot, the maximum PID loop speed is 4 kHz;
• the threshold for activation of the yaw spin recovery feature has had an automatic mode added - this mode sets the threshold to a value that is based on the currently configured maximum yaw rate, with a buffer added on top of it. This new mode is the default for yaw spin threshold, since it provides a setting that is safe to use for most users. Manual configuration of the yaw spin threshold is still possible;
• accelerometer calibration is now required before arming is allowed if any feature is enabled that requires the accelerometer. This is to prevent situations arising where the craft may try to self-level with an uncalibrated accelerometer, leading to unexpected or dangerous results. Arming will be disabled and a warning displayed in configurator until the accelerometer has been calibrated;
• the calculation for the virtual current meter device has been changed to be based on the throttle value used in the mixer, instead of the throttle channel RC input. This means that this value has things like throttle limiting and throttle boost applied, resulting in more accurate prediction of current and consumption. If you are using the virtual current meter device, make sure to calibrate it again after updating the firmware to make sure the calibration is still correct;
• the way that the 'RSSI dBm' value is tracked in the firmware has changed to use actual dBM value in a range of -130 to 0, instead of the previous version's 130 to 0 range. This means that if a custom setting for osd_rssi_dbm_alarm is used, this will have to be changed to be the inversion of its previous value (e.g. 60 becomes -60);
• since stick arming is not recommended for multirotor craft because it can lead to accidental disarms, it has been disabled by default. If you want to use stick arming (at your own risk), it has to be enabled by setting enable_stick_arming to on;
• the name CLI command has been removed. Use set name = <name> instead.

Major Features:

• completely reworked the gyro loop, improved performance and made it always run at the native speed of the gyro;
• added new selectable ACTUAL and QUICK rates models;
• added compensation for sagging battery voltage, resulting in more consistent throttle / PID behaviour over for the entire flight time;
• Added level race mode ('NFE race mode' in Silverware).

Minor Features:

• added the option to display the OSD logo on arming;
• added support for enhanced OSD / CMS devices, made it possible to support highligting of text or symbols;
• added support for FrSkyOSD OSD devices;
• added support for the Redpine RC protocol on devices with an SPI connected CC2500 chip (FrSky SPI).

Changes from the previous Release Candidate:

• fixed incorrect reporting of configured / detected OSD device over MSPl;
• added missing pin ownership checks for I2C;
• fixed typo in CLI help command;
• increased the minimum values for gyro_rpm_notch_q and dterm_rpm_notch_q to address problem with too low values causing runaway acceleration;
• fixed problem with setting negative values in CMS;
• fixed incorrect value ranges for battery offsets in CMS;
• fixed connection loss problems for ublox GPS.