DMX RS485 Wrong Board Fix

This is a fix for my other tutorial : ” DIY USB DMX INTERFACE FOR UNDER $10“, apparently there are multiple versions of this board being sold. Depending on what site you bought it you may or may not have received a working chip. For those who are stuck with a non-working chip, this is a guide on how to modify yours to allow DMX data output. Solution found by GermAndy!

Requirements
– non-working RS485 USB Board
– Soldering Iron, Tin
– Steady hand

The Problem
There are different models of the USB RS485 interface being produced. Some of these models will not work out of the box and need some small modifications to  work. I have not yet found a way to identify these boards but here is a fix thanks to GermAndy.

rs485board

The problem seems to be with the 75176 chip:

pinout75176

The problem is with the DE pin… because the DMX data is a bit different from the original RS485 protocol. the DE pin does not raise because the RS485 protocol is not properly ended. This means there is no data send out as long as the protocol has not ended it’s stream correctly.

Solution 1

Lifting the DE / RE pin from the board. Lifting the DE/RE pins from the board will allow the 75176 chip to put out DMX data without waiting for a verification of the protocol. In most cases this solution should work. If for some reasons this did not work try solution 2.

Some boards still don’t work after lifting the DE/RE pins, Solution 2 fixes these boards:

Solution 2

If solution 1 did not work, you have to connect the DE/RE pin to the +5V of the 75176 chip. Since the chip is very small it’s recommended to use a soldering iron with a small tip. the +5v is the VCC pin on the chip diagram :

rs485chipmod

Image by Germandy

Fix For Mac(by David P.)

So basically here are the steps for future readers:

On MacOS X (El Capitan)

* install D2xx Driver http://www.ftdichip.com/Drivers/D2XX.htm (read carefully the README file which is included – lot of manual steps in a terminal)
* install D2xxHelper http://www.ftdichip.com/Drivers/D2XX/MacOSX/D2xxHelper_v2.0.0.pkg
* Reboot
* Install and start QLC+

Everything should be fine. If not, also follow instructions on https://stevenbreuls.com/2014/03/fix-ftdi-dmx-interface-arduino-on-osx-10-9-mavericks/

Best

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christian piva
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christian piva

For me, only the 2nd solution works.
The chip mounted on the board (ordered to DX) is: T485EEN.

May be, the universal solution is to replace the chip with this: MAX481ECSA+ ( Farnell, 9725130 3,53 € )
Thanks.

paky
Guest
paky

hi I’m from belgium. I have the save interface and it don’t work. I don’t have good english . Can you explain me what is exactly “lifting the DE/RE pins from the board” how to do that.

ihbar
Guest
ihbar

I found another option : On my board, the RE/DE are connected to output C2 of FTDI chip. Instead of desoldering, you can use FTDI software FT_prog to change the pin configuration. Then you don’t need any hardware change.
Details are here : http://falconchristmas.com/forum/index.php/topic,858.msg9877.html#msg9877

ivan
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ivan

what’s your chip? mine is sp485ee

thomas
Guest
thomas

Lifting pins 2 and 3 worked for me. No luck with FT_prog. Production date 2013/06/4 as mentioned by others with this issue.

Additionally, in OSX, I needed to unload FTDIUSBSerialDriver.kext, not sure when or for what I installed it but it interferes with the ftd2xx drivers.

Thanks for the great post Steven and solution GermAndy!

Daniel
Guest
Daniel

Thanks a lot. Solution 1 helped, I nearly threw it all away !

Bee1derful
Guest

I’ve tried to use the ft_prog way but when I check C2 is still TXDEN instead of SLEEP. Why is this?

alexis cid
Guest
alexis cid

cause your ic is clone and the new ic has eeprom bloqued. its because the ftdi campany has make a drvier that erase the chip clone. so, the chinesse have bloqued it.

Arechigav17
Guest
Arechigav17

I use the very chip described at the begining and it work pretty well out of the box. BUT! After working perfectly 2 to 3 minutes, sometimes a little more,it will stops sending. The software and the computer itself say that the hardware it’s still connected but it won’t send. As soon as I unplug and plug back the USB from the computer or the “unit” it picks up again and works for another little while. Does anyone have any idea that can help me out?

Arechigav17
Guest
Arechigav17

Probably, I’ll try that!

Arechigav17
Guest
Arechigav17

I tried a different pc and still did the same thing; work for a little while and then freezes. Any suggestions, maybe some setting that I might be able to load with tge FT_Prog. Like I said, all I’ve done is installed the driver and it worked, but it has that problem. Any suggestions on anything that I can try. I really appreciate this.

Jesse H
Guest
Jesse H

did you figure it out? i’ve got two modules with exactly the same problem.I have no dmx terminator lying around, but the module will stop after a while for 10 seconds and then proceed again, even without any lamp connected. If it stops, the rx led is not blinking. Once it resumes, the lights comes up again.

Weird thing is that the 3d visualiser also stops working (it did however work without any interruption when i was only ‘dry testing’ with a virtual adapter

Henry P
Guest
Henry P

For solution 2 do you first have to lift the DE pin and then connect it to +5V or do you have to leave the DE pin connected to the board and then link it to the +5V pin ?
Thanks.

Kevin
Guest
Kevin

What is the proper replacement chip for this, which requires no modification? I bent the leads up, but one of the leads broke. So I can’t try Solution #2. Now I must replace the chip anyway.

Since I’ve already come this far, I’d rather repair this board than to start a new project.

gabe
Guest
gabe

Hey Steven,

Im having a bit of a problem trying to get this working. Ive done all the steps but my light just flashes when i plugin the usb cable to the computer.

gabe
Guest
gabe

yes i tried it at 20 and it still does it

Murphy S
Guest
Murphy S

Hi Steven
I tried many other ways to solve my problem and this only worked !! And not needed another source of feeding only the weld. I paid $ 3 in alli express and rode my dmx dongle I am very happy , thank you for your help Thank Brazil .

pepe
Guest
pepe

Hi Steven. i bought a new one usb to rs485 ….. but my fix does not work ( because it was already shorted) ( point of that is that chip can not reset it self… ( it should be only two shorted pins as i understood)

now testing De/Do of level translator ( wich i gues it is) shorting to +5V…. and i recomend shorting it to main rail ( it is easyer to solder…. will provide another feedback)

Arrigo Horta de Nájera
Guest

hey. i have lifted the two pins and the adaptor works for about a minute and then crashes. I have tested in 3 computers and the resoults are the same. Should I sort it to the 5v now or I have another problem?
Thanks

Luc
Guest
Luc

I tested a new batch of adaptors with QLC+. Not working out of the box with windows 10 and default driver. Re-programing the chip failed, chip locked. Only solution 2 seems to be working… Seems to be unstable, has disconnected after a while. Re-booted on Linux: I tried Ubuntu 16.04: Adaptor works out of the box. Stable Booted on the Raspberry Pi 3 with Raspbian Jessie: Adaptor works out of the box. Stable I would say that the problem seems more related to the windows driver than to the interface itself. Or that default linux driver is so ‘elementary’ that… Read more »