I bought a TRONXY X5S in December of 2017. I knew it would need updates and changes so I expected to have to upload new MARLIN code into the machine. Wizard has posted a working version of Marlin 1.1.8 setup for the X5S (THANKS!!!!) The link to this work is found at: https://www.thingiverse.com/thing:2738690
As suggested as a problem in Wizard's post, I too found out that my X5S unit did not have a bootloader installed. This meant that I could not "talk to the X5S" from the Arduino IDE; that is, it was NOT ready to accept new programs or updates..
After doing much web research, I figured out that I needed to have an ISP (In-System-Programmer) with which to burn the bootloader. This is done using the PROGRAM HEADER on the Printer Control Board (AKA the MELZI board) and NOT the normal printer USB connection.
A search of eBay revealed many inexpensive ISP programmers but none seemed to be compatible with the Atmel 1284P.
Fortunately, almost any 5 volt Arduino board can be made into an ISP. In the attached PDF file, you will find my notes on how I on built an ISP out of a NANO V3 board. (Use the WEB for to find the details for using an UNO or MEGA, or what ever 5V ATMEL board you may have on hand). These notes show the steps needed to build the ISP, load it with ISP code, and then use it to install the bootloader into a Melzi board. I also cover uploading new Marlin code into your X5S/Melzi board.
Unfortunately, this is a lot of screwing around to get going. However, the good news is that you will only need to burn the bootloader into your printer control board ONCE. That is, once the bootloader is present on the MELZI, you can use the Arduino IDE directly (through the normal USB connector between your PC and your printer) for all future uploads and updates of the MARLIN code into your printer.
You must use great care building and connecting the ISP to your MELZI board. An error in wiring or interconnect between your ISP and your MELZI board may permanently damage your X5S MELZI board, the ISP you've built, and/or your PC!!!
You must compile and install a special ISP program onto your Arduino NANO (or UNO, or Mega, or...) BEFORE you can use it to load the bootloader into your MELZI.
You must have the SANGUINO support files installed into your Arduino IDE or you won't be able to compile code for the X5S and then load the code into your MELZ board.
TAKE CARE: Once you use the ISP to install the bootloader onto your MELZI, your printer will CEASE TO FUNCTION as it had from the factory. A new version of MARLIN must be loaded (using the Arduion IDE) before your printer will come back to life.
You must have new Marlin code and a valid X5S Configuration.h file ready to go in your Arduino IDE. Make sure it compiles without errors before going on. Note that without a valid Configuration.h file loaded with all of the important X5S settings, the Marlin code you load WILL NOT WORK. See Wizard link above for a working X5S code and Configuration.h file set to use as a starting point.
- If any of the above items scare you, do more research and/or get the help of a friend that has been through this process before.
Although I have succeeded installing the bootloader and getting my X5S updated, I am NOT an expert and my notes may not cover everything you may need. They do represent the detailed steps I worked up based on my web searches and they worked for me. I am posting them with the idea that they may help others as well.
Take care, go slow, and best of luck!.