# How to choose which form of data transmission I should use?

#### Kailand09

Joined Jul 30, 2012
8
I have done a few searches, and I understand the basics of the different forms of device communication, but need some advice on which route to take.

As an engineering student, I'm quite sick of doing nothing practical, and decided to fool around with some different random ideas to see if I can get them to work. I am currently working on an intercom-type system that will reside within my home's current wiring, and cannot decide on which form of communication is most appropriate.

Obviously, sound will be a high priority, and I definitely want the best quality possible. On the other hand, I want speed to be fast, as I may end up using the voice bits to try and interface with my phone's speech software to try out some android application developing.

The third thing I've been looking at is, as in any engineering, price. Looking at WLAN modules, a quick search in digikey yields:

http://www.digikey.com/scripts/dksearch/dksus.dll?KeywordSearch

The Maxim chips seem the cheapest, but from what I've read most people recommend the Microchip:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2885¶m=en547232

Which seem to run at $25-30 a pop. If I want to fill every room in my house, I'd rather not get at high as$20 for one IC on each board. I understand components are highly dependent on scale, but what are the major differences here? I believe the Microchip is a full module, and they have a free API. Does Maxim not have an easy to use API? Would I need to design antenna circuitry with the maxim? How difficult would that be?

On the other hand, if you look at power line transmission, there are also lower priced chips. I haven't heard much about how the programming goes with those, are there dedicated API's? From what I've read, they are also limited a lot more than using WLAN, such as interference or, in the case of X10's systems I read about, neighbors may fight for power bands.

Would it be better to go the non-802.11 RF route? Those seem to be cheaper as well, but then again they also don't seem to have as much laid out for you like some of the WLAN modules do for easy programming etc., and sometimes require more infrastructure.

For power line, I know distance isn't as big a deal inside my house, whereas WLAN may give me troubles, same as other RF bands.

I've also read of people getting high transmission speeds using PLC, higher than WLAN, but whenever I read datasheets for the PLC IC's the highest i've seen is 57,600 baud?

In pricing, most company's websites require you to be a business and high volume to get a handle on their products, does it get much cheaper than that Microchip? How does a small guy get a hold on the cheaper chips?

Sorry for the long post, I'm just trying to be descriptive in the million questions that come up which I cannot find answers to, so that you guys know where I'm at.

Thanks!!

#### Kailand09

Joined Jul 30, 2012
8
I forgot to mention -

Another thing I am considering is the amount of devices, which would be at least one per room in my house. It may become difficult to network a decent number of devices together, even if my house isn't that large with lots of rooms.

#### MrChips

Joined Oct 2, 2009
24,405
Have you looked into Zigbee?

#### Kailand09

Joined Jul 30, 2012
8
Yes I have looked at those, they are pretty well priced, would something like the ti cc2250 be appropriate ? I see it lists 400m line of site, which seems reasonable. Would 250kbps be quick for transferring voice and maybe a few other commands? I did see an atmel chip with 2mbps, but required a separate antenna whereas the ti had one built in right?

#### MrChips

Joined Oct 2, 2009
24,405
A bandwidth of 5kHz for voice is adequate.
Hence 12 bits at 10ksps = 120kbps is all you need.

If you are looking into voice transmission, you want to look at delta-modulation.

#### Kailand09

Joined Jul 30, 2012
8
Thank you very much for three pointers, much appreciated . It does seem xbee is the most sensible route .I have noticed the atmel atzb-24-a2r appears good since I definitely don't want to try and design antenna . I will have to look around some more at different ones that may apply better to my application, but otherwise that is only about 15 for multiples of one.

One question I still have, these guys all come with on board micro controllers, can I utilize those to program to, or should I still have a separate dedicated micro controller for my application?it could definitely save some cost if I don't need to but a separate ic for that.

#### BMorse

Joined Sep 26, 2009
2,675
If you go with using Zigbee, one thing comes to mind, how will you interface your android device to that (without directly connecting your android phone to a zigbee module)?

#### Kailand09

Joined Jul 30, 2012
8
Well that's a good point. My mind slipped a little here. With wifi modules I could have just ridden my home network that already exists. Would I need a big clunky router or modem like my home WiFi to run a zigbee network? Otherwise, I suppose I could just connect one through serial to my pc and then send commands through my WiFi to my pc which then could relay to each room?

#### BMorse

Joined Sep 26, 2009
2,675
You could do it that way or, you can just have a standalone Zigbee to WiFi module that would take care of the communications between your home Wi-Fi and your devices, you could design that as the main "server" that takes in the commands/instructions, and properly route them to the appropriate device in the house, or gather info from a device and send it out via Wi-Fi, etc...

#### Kailand09

Joined Jul 30, 2012
8
Hmmm that is another good option. I'll have to sit on that idea when I'm looking into parts later today to decipher my cheapest route. Cost is really what I'm going for here . I'm a cheap college student lol.

#### BMorse

Joined Sep 26, 2009
2,675
Hmmm that is another good option. I'll have to sit on that idea when I'm looking into parts later today to decipher my cheapest route. Cost is really what I'm going for here . I'm a cheap college student lol.
these devices although will be placed in separate rooms, I would assume that they would all be identical in purpose? If so, then start with 1 room and the "Server" station, then whenever it is within budget, just add another room module, till you get the house filled! , anyway, starting out with just one room controller/device would be a lot less aggravating when trying to build a prototype, best to keep it as simple as possible to start, then build on that.

Another option (to keep it low cost) do just a standard RF communication between "server" and modules (check out linx technologies for their lines of RF modules) these will be a lot cheaper to implement than zigbee or Wi-Fi modules for each device, then you can just use a stand alone Ethernet IC (like the ENC28J60 by Microchip or something similar or newer) with a pic to interface your device "server" to your home network, then you can just access it via your home Wi-Fi router.....

I am currently working on a project for my outdoor wood boiler, and this will have an RF transmitter/receiver to update the boiler status and such to the wireless controller I will have inside the house, this way I can see the status of the boiler without having to go outside in the winter.... I thought about using the X-10 protocol over my home wiring, then I looked into zigbee and Mi-Wi, then I finally settled on using some 433 Mhz Transmitter?receiver modules from Linx Technologies, I purchased the modules and matching 1/4 whip antennas fro Digikey.... still have to get them implemented into the project once I get done fine tuning the Thermocouple sensors and NTC sensors.....

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#### Kailand09

Joined Jul 30, 2012
8
That is definitely a good route I will go, trying to network multiples right off the bat is no good. I'm currently running an Arduino with some software written, and I'd like to get a wireless chip running as soon as I can because it is hard to do much with data handling since it will all need to exit out the RF chip. Then, if that works really well and I can interface with my PC maybe a simple GUI, then I'll scale up to more rooms.

The linx modules look pretty nice, I see this one:

http://www.mouser.com/ProductDetail...-433-LC_/?qs=sGAEpiMZZMsprRPEdcYqImCkkmchJB0z

is quite cheap. The only issue is an external antenna is needed. Would this be similar to the antennas on old school routers with semi-hefti size, or just those thin wire ones that pop on a PCB? In the end, I'd like this circuitry to fit inside my wall if it works well enough, meaning I don't want a big honking antenna sticking out. I'm hoping this whole project can help me to learn some PCB design as well, so I think I may try to order a few from pcb123 or similar site that allows me free design software.

Also, do these come with easy API's to use and control them?

EDIT:

it seems the linx module with antenna and ease of use is this:

http://www.mouser.com/ProductDetail/Linx-Technologies/TRM-315-LT/?qs=sGAEpiMZZMuIes%252bYBRf57WDgGiWNXYe9aitX9%2fUC5zI%3d

which appears actually more expensive than the zigbee module?

Also, it appears to transfer voice this zigbee is made precisely for my application. I have never seen/used CEL products before, any opinion on them?

Here is the link:

http://www.mouser.com/ProductDetail/CEL/ZICM2410P0-1/?qs=sGAEpiMZZMvLuvXCNB77x2%2bwfCHdbOHh

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#### BMorse

Joined Sep 26, 2009
2,675
just an FYI, happened to be browsing sparkfuns inventory when I happened upon this >> https://www.sparkfun.com/products/10822, it may be a "low Cost" Wi-Fi solution for your "Base station"...