On June 26, 2013 Canon Inc. released a firmware update for the EOS C100, which contains XLR terminal modifications, continuous auto focus and continuous auto iris.
A function has been added which allows automatic, continuous focusing and iris settings on a subject in the center of the screen when using the EF-S18-135mm f/3.5-5.6 IS STM lens. Focus can now be continuously held on the subject when the interchangeable lens EF-S18-135mm f/3.5-5.6 IS STM is attached and the focus mode switch is set to AF. Additionally, the iris setting will now adjust as needed.
Also, the polarity of the XLR terminal has been modified to improve compatibility with external audio devices. This XLR pin configuration meets the international AES standard recommendations. The firmware update will avoid the scenario where the unit, if used in combination with a device of differing polarity of the XLR terminals, would result in weakened sound levels due to a reversal of the phase relationship.
Firmware download, preparations, and requirements available on the Canon web site.
*Firmware Version 188.8.131.52.00 is for EOS C100 cameras with Firmware Version 184.108.40.206.00. If the camera's firmware is already Version 220.127.116.11.00, it is not necessary to update the firmware. Once the camera is updated to the latest version, it cannot be restored to a previous version.