There’s no way to directly update the cable, but it should update automatically when plugged into your Mac. While you can check the firmware of your power adapter by attaching it to your Mac and clicking on the Apple logo in the top left corner of the menu bar, then About This Mac, System Report, and Power, it’s not clear how to check the specific firmware version of the cable.
So presumably there is some UART to the cable, and the cable to the power adapter. Is it all stuffed in the cable treated as a USB device or is there some proprietary control on the laptop side to communicate with the cable?
The chip uses the 1-Wire protocol, which is a clever system for connecting low-speed devices through a single wire (plus ground). The 1-Wire system is convenient here since the Mac can communicate with the Magsafe through the single adapter sense pin.
The only interface the computer normally has to the cable is the single control pin on in the middle of the MagSafe connector, so they are likely having to do something more sophisticated than UART.
(Apple could have had you plug the other end that has the USB-C connector into the computer to do the firmware update, but that isn't particularly intuitive or user friendly).
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There’s no way to directly update the cable, but it should update automatically when plugged into your Mac. While you can check the firmware of your power adapter by attaching it to your Mac and clicking on the Apple logo in the top left corner of the menu bar, then About This Mac, System Report, and Power, it’s not clear how to check the specific firmware version of the cable.
So presumably there is some UART to the cable, and the cable to the power adapter. Is it all stuffed in the cable treated as a USB device or is there some proprietary control on the laptop side to communicate with the cable?
http://www.righto.com/2013/06/teardown-and-exploration-of-ma...
Magsafe 3 with USBC makes this even easier https://www.reddit.com/r/UsbCHardware/comments/11309f3/comme...
The Lightning comms protocol is interesting too https://hackaday.com/2015/02/14/reverse-engineering-apples-l...
The only interface the computer normally has to the cable is the single control pin on in the middle of the MagSafe connector, so they are likely having to do something more sophisticated than UART.
(Apple could have had you plug the other end that has the USB-C connector into the computer to do the firmware update, but that isn't particularly intuitive or user friendly).