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RS232 Option & Connecting to your own uP (1 viewing) (1) Guest
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TOPIC: RS232 Option & Connecting to your own uP
#484
RS232 Option & Connecting to your own uP 7 Years, 10 Months ago Karma: 7  
A true RS232 Version of the AD2USB is now available on our online store. If you need to connect the AD2USB directly to another uP or some other system then the following information is for you.

USB is very sensitive to EMI a sad but known fact. I have a few people who have mentioned that sometimes they loose connection to the device. This has been solved most often by adding a usb 1.00 HUB to the mix or putting the alarm panel or computer that is hosting the AD2USB on a more isolated power outlet or move the offending device on to a different circuit such as your Blender

USB is just not very good at dealing with EMI noise. If noise gets on the USB bus through the power form the panel it can cause a broken message that can shut down the USB host controller chip. This would never happen with RS232 you would have to vaporize the circuits with a voltage spike to get it to stop.

To connect directly to the AD2USB you can use this connector expansion connectors Part data here or you can order an breakout adapter from our store.



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#485
Re:RS232 Serial Option now available. 7 Years, 10 Months ago Karma: 0  
alright, i just put mine on a 20p panel..
Thanks for shipping it so fast.

What are the default RS-232 settings this uses?

thanks,
dan
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#486
Re:RS232 Serial Option now available. 7 Years, 10 Months ago Karma: 6  
USB is very sensitive to EMI a sad but known fact. I have a few people who have mentioned that sometimes they loose connection to the device.
I hadn't seen this mentioned in the forums before, but it seems to affecting me also. I've been losing connection so frequently, I have a script to restart the USB device daily.

I'd like to learn more about this if possible. Is the problem on the PSU of the alarm or computer, or both? Would a surge protector alleviate the problem (my PC already has one in addition to UPS).

I'll give the USB hub a try as it's connected directly currently. I had thought that the USB cable had a ferrite bead to stop EMI, is that not sufficent?
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#487
Re:RS232 Serial Option now available. 7 Years, 10 Months ago Karma: 7  
Hay guinness sorry you have this issue. I do have several things to try that should help. In the future if you do see odd stuff please let me know so I can help

The alarm seems to pass along any AC noise it gets from its wall adapter down the DC supply lines for its devices. The type of noise that gets through is mostly caused by motors like from a freezer pump or in my case an old school desklamp with a switches on my lab workbench. This noise does not effect the CPU of the AD2USB but does get onto the TX/RX lines of the FTDI chip. The noise exists on both the positive and negative supply lines so filtering has to be done on both. I have looked into a bead that would be used on the DC supply lines from the panel or adding an additional voltage regulator between the AD2USB and the alarm panel.

In future hardware releases if/when I sell all I have now I have some changes planned that will reduce this problem by isolating the FTDI chip power and ground from the rest of the board as well a modification to one circuit that is currently directly connected to the 12V line from the panel that will allow powering the device from cleaner power.

Distance from the noise producer to your alarm panel will help. I have talked to others who have seen this problem not necessarly with my device but ftdi chips in general. Putting an inexpensive HUB between the FTDI chip and the computer fixes the problem in many cases but you have to expect that the noise is still on the line so its best to try and find the source of the noise and fix it. Not all hubs work so if you have some to play with around the house give a few a try.

USB has a bunch of two way chatter back and forth even when you are not sending data. If this communicaiton breaks down or they loose a specific message "some" USB host controllers on "some" computers will shutdown and stay down till a reset is ussued. In some cases I have heard that some USB chips types need a physical reboot but most newer USB host controllers do better.

So for starts get a 50' extension coard and plug your alarm into it see what that does. 50' is excessive but it will prove a point if it fixes the problem.

In my case I also noticed the issue on the PC side of things where I had an AC transformer powering my yard watering system that was leaking noise on the AC just inches from my DC power supply that powers all of my home automation system. This is not the norm and most PC power supplies are very good about noise reduction.

Hope this info helps if you find anything that works let me know so we can tell others.


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#488
Re:RS232 Serial Option now available. 7 Years, 10 Months ago Karma: 6  
Thanks for the comprehensive reply Sean, I can't commend you enough for your after sales support. I'm not that worried by the problem, but it would be nice to get a resolution!

To be honest there are so many moving parts in modern systems (with varying chipsets, controllers and 3rd party components/drivers) it's no wonder there are problems - maybe that's why Apple likes to stay in the hardware business.

So I have empathy for anyone producing peripherals that are reliant upon other systems. My DC adapter is already 25ft away from the panel as it's in the garage. It could be on the same circuit as the door opener which would be interesting to test out.
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#491
Re:RS232 Serial Option now available. 7 Years, 10 Months ago Karma: 6  
Update: So I tested the USB hub theory out. Without one, the connection dropped on three attempts (approx 5, 8 & 10 hours respectively).

With the USB hub in I've been running for about 3 days now without issues - fingers crossed! The garage opener didn't faze the connection either.
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