ALIBE uses AC4790 as its onboard communication module. AC4790 is a Transceiver able to communicate with another AC4790 at varied Baudrates and with a clear line-of-sight, is able to get a range of 4 miles. This clearly was one of the factors that helped me decide to go with it as opposed to other products in the market. There are other benefits of using AC4790 from future scalability standpoint. One, it is fairly easy to work with compared to other competitive products in the market. It’s Pin layout and Pin characteristics are easy to follow. And, mostly, can be effectively functional just with 3-wires into the microcontroller. It has many featuers. However, for ALIBE, all he needs to do is wait for commands from homebase Command Center and either react to the commands or send data back. A very “Reactive” behavior. For something as simple as this, one is able to make this work with 3-wires. The second reason I chose this was, the range. In a clear Line-Of-Sight, ALIBE is able to keep the communication open for upto 4 mile radius – which is very useful for ALIBE’s behaviors and Thirdly, AC4790 supports not just “Peer-To-Homebase” but, also, “Peer-To-Peer”. So, if in case I were to build another ALIBE, the two will be able to communicate with each other and also with the homebase Command Center effectively. This last feature is very useful for the future of ALIBE.
So, how did I get started with AC4790?
Well, like many out there, I started asking people and searching web sites for recommendations. I was given a pointer to Aerocomm by a couple of folks in the Parallax forum. I called Aerocomm technical support – BTW, very helpful folks over there. I laid out what I was looking for in my project 1) Range 2) simplicity in interfacing 3) scalability from peer-to-homebase and peer-to-peer and of course 4) cost. Aerocomm has many products under the Transceivers umbrella, however, from the discussions with the Tech support, I determined that AC4790 meets most of my requirements if not all. Cost being one of them that was not that great. But, overall, I felt AC4790 is a good match for what I’m looking to get and do.
I was very new to this long range radio communication field and definitely my handicap was also that I’m not that strong in electronics (always learnign new stuff). So, in order to speed up my learning curve, I decided to buy Aerocomm’s System Development Kit for AC4790. The kit comes with everything you need to get a good handle on things. It comes with two dev boards fully loaded, including AC4790 mounted on each, power adapters, USB cables, Serial cables, manuals, software and even a great carry case. I thought this was a great deal. I paid, $199 USD to get this kit. Which did not seem too bad at all. BTW, I don’t own any stocks of Aerocomm or any special interest. Just a kicked up hobbyist.
The dev boards can be powered using USB alone – which is what I do everytime I test my stuff up.
To start things out, I hooked up the dev boards via USB to my laptop 2 separate USB ports. Kicked off the app that came with it and voila, I was able to send and receive data back and forth from the two dev boards. The software also allows you to view/edit the EEPROM settings (these settings define the core behavior of the AC4790 chip) very easily. It also shows the address of which setting you’re modifying and the definition of the settings (that is what is does and how it impacts the behavior of the chip). You can also get this information in the manuals.
It is worth noting that the dev boards and the AC4790 can operate at various choices of Baudrates. Keep in mind that I had to bring down the baudrate a few notches (4800) when I started interfacing AC4790 with my Propeller chip.
Once I got a good feel for the chip and how they work, I took out one of the AC4790’s from one of the dev boards and started to think about building a carrier board for my Propeller interface. Which is another posting in this blog.
If you’re looking to using AC4790 in your own projects, you want to keep a few things in your mind
- Read their manuals – found in their site above. There’s the Kit Manual (that explains the dev board and the Software) and then there’s the AC4790 User Manual and DataSheet. Pay extra attention to the data sheet of 4790. Both are very well written.
- In the AC4790 manual (you can get one from this blog), pay special attention to the Pin Configuration. For a simple Tx behavior, you only will only need to tap into a few pins out of the 20 pin lot.
- 1 (Session Indicator),
- 2 (Tx – from Propeller to AC4790 device),
- 3 (Rx – from AC4790 device to Propeller),
- 5 (GND),
- 9 (Rx Indicator),
- 10 and 11 (both need to be 3.3v VDD). and that’s it.
- I needed pins 1 and 9 for my LEDs (pic below).
- My carrier board (very simple one BTW), has soldered LEDs and also exposes the pin 1 and 9 (as pin 1 and 4 carrier board) – if in case I need to further use those pins for future work. I am happy w/ the way it turned out.
You should be able to find more posts on my blog that talk to, “How to interface AC4790 with Propeller” if you are looking to find out how I did it in ALIBE.