If you are going to be updating firmware frequently, I can recommend these…
I must have updated the firmware hundreds, possibly thousands of times already, since I’ve not writen a TNR emulator, so have to test on the hardware directly. Given that this involves inserting and removing the SD card, and switching the TNR on/off, there is a lot of scope for breaking the SD slot or the power switch due to mechanical wear. The power switch in particular is very difficult to replace, as to desolder it you have to desolder the whole LCD panel (as confirmed in the service manual, and also shown here: Youtube ).
So, because I don’t want to damage my TNR during testing, I use an SD card extender :
I also use a DC in-line power switch, with 2.1mm connectors, often used for LED strips :
Both of these enable me to avoid wear on the TNR, and are easy to replace when they fail. Both of these items are readily available, and represent very cheap TNR insurance !