Huawei PSU4850A power supply control - Page 1
Forum section: electronics / projects

author: jmibk
author_rank: Regular Contributor
timestamp: March 03, 2020, 05:44:38 pm
content: I have a Huawei PSU4850A power supply - manual can be found here:http://www.audiowerk.at/downloads/temp/hannes/PSU4850A-Rectifier-User-Manual-V1_0.pdfThere is the ability to control some specs (like output voltage) via RS485, I like to use.I found out, that the communication protocol is called "Modbus", I also found the pinout in the manual:Thats if you look directly on it.I used a random USB to RS485 adapter I have here, I conected it to GND, RS485+ und RS485-. I'm not shure about the polarity, because it has an XLR connector on it. On a terminal program like Termite I get "0" (zero) if I press enter. If I swap + and -, I get nothing on the screen. So the polarity is clear (I think).Settings are 9600 and 19200 Baud 8N1. Both settings same result. From now on I tried both baud rates.After that I tried QModMaster Software for some more investigation. It shows always some errors.There are also some (5) address pins on this data connector on the supply. They are high (3,3V) and can be pulled low. I don't know if a low state means 0 or 1. I tried both (pulling A1 to A4 down, pulling A0 down, pulling all down, leaving all up), but no difference here.Now it was time to test the RS485 signal - here it is and it seems to be ok and it is a RS485 and no RS232....On the scope thats the bits sent by the modbus software if I press the green play button on the right window. I also tried switch this address number and did a scan, that returned an error. There is also no answer from the PSU on the right side of the scope plot if I zoom out.Does someone know this kind of supplies, knows someting about the communcation and what can be wrong here? Does someone have a command sheet for these kinds of PSU? There are many on the web but they correspond to UPS systems. Every hint may be useful

author: fcb
author_rank: Super Contributor
timestamp: March 03, 2020, 06:42:33 pm
content: MODBUS has an address range of 0 to 9999 - the address selection maybe offset. Your 5 bit address might not corrospond to ADDR: 0-31, but might be ADDR: 5000 to 5031, etc.. Huawei probably use the same MODBUS for other housekeeping in the same cabinet.

author: AlexHun
author_rank: Newbie
timestamp: February 28, 2025, 08:38:34 pm
content: Hi!I was wondering how you managed to get the communication to work? I have one of these power supplies, but unfortunately I've been trying for two days now, but I haven't managed to establish a connection...

author: prasimix
author_rank: Unknown
timestamp: March 01, 2025, 09:38:06 am
content: EEZ Studio supportsModbus, i.e. you can create your own dashboard with all desired controls and use USB-to-RS485 converter to access your Power supply.

author: AlexHun
author_rank: Newbie
timestamp: March 01, 2025, 09:57:50 am
content: Hi!My current problem is that I can't communicate with the power supply using any software, I tried Modbus poll and many others, I just don't understand why.....

author: Mazen
author_rank: Newbie
timestamp: July 25, 2025, 01:09:51 am
content: please if you found a solution... let us know...I found only this link... it could be useful...