I worked with the XY-FZ35's serial port last night for a couple of hours trying different combinations & permutations of the setup commands. I tried single commands, all commands on a single line, and variations of commands on a single line.
No success. In-fact the results were worse than a total failure because sometimes entering a setting command would produce a "fail" output immediately followed with "success" on the next line. But even that weird behavior is not consistent every time. At no time was I able to change any of the settings. I tried the CH340G USB/UART with different USB cables and even plugged it directly into my laptop's USB port, that didn't make any difference. I tried powering the XY-FZ35 from different sources including a 12V battery. That didn't make any difference. The control serial commands always work as expected. Tonight I will fire off emails to China to see if DROK or IC-Station can help with this (I put the emails off until I spent some real time trying to make the setting commands work). Here's where I am right now...
* The serial port always works OK for the following control commands:
start, Start data output
stop, Stop data output
on, Turn on the load function
off, Turn off the load function
read, Read product parameter settings
* The serial port always FAILS for the following commands:
x.xxA, Set load current
LVP:xx.x, Set low voltage
OVP:xx.x, Set over voltage
OCP:x.xx, Set over current
OPP:xx.xx, Set over power
OAH:x.xxx, Set maximum capacity
OHP:xx:xx, Set maximum discharge time
* Here are my terminal emulator and USB/UART settings. I am using a CH340G USB/UART module set to 3.3V in Windows 10. The serial connection with the XY-FZ35 load is working OK in both directions:
- Set the USB/UART module to 3.3V TTL levels.
- Cross TXD and RXD lines.
- COM Port: 15 (Yours will Vary)
- Baud Rate: 9600 bps
- Data bits: 8
- Stop bits: 1
- Parity bit(s): None
- Line Termination: LF (Line Feed). Note; LF, CR, and CR+LF all work.
- Hardware Flow control: None
- Software Flow control: None
- Local Echo: ON
+------------+ 3.3V +--------+
+-------------+ USB | RXD|-->>--<<--|TXD |
|PC/Laptop USB|--<<---<<--|USB/UART TXD|-->>--<<--|RXD FZ35|
+-------------+ | GND|-->>--<<--|GND |
+------------+ TTL +--------+
Fig.-1, XY-FZ35 Programmable Load Serial Port Interconnect
* I used Termite, a simple RS232 terminal emulator for Windows (link below). I also tried Hyperterminal which works OK when copied over to Windows 10 from a Windows XP machine. Both terminal emulators give me the same result. Here's a link to Termite, it's free. Termite can be installed or run stand-alone:
https://www.compuphase.com/software_termite.htm