N8VEM Computer With A 3Km Wireless Link


[James] sent in this project in which he built a tiny computer with text based OS and a 3Km wireless link. The details are a bit scarce, but he used an N8VEM, a Propeller Pocket Term, a 4 line LCD and an RF Transceiver to build it. It runs CP/M, the text based operating system and uses less than a half of a watt, without the vga monitor. With a total cost of 145 and 4 serial ports for sensors, this thing could come in handy. Especially since its low power consumption could allow it to be solar powered.  You may recall the N8VEM from an earlier post we did.

26 thoughts on “N8VEM Computer With A 3Km Wireless Link

  1. I like this thing. But it could use a case. maybe the keyboard. put it behind and then put the mini lcd where the caps lock, num lock, and scroll lock lights are. (move them above the f keys) and put the solar panels(if you want them) around the lights. i’m basing this around the keyboard in the picture.

    also, need more info! especially the os. could come in handy.

  2. Hmm… My old Kantronics KPC-3 could run for a day on a 9V battery, could hook to any radio that had a hand mic and headphone jack, and only needs a serial terminal to connect to other packet stations or send mail. It even has its own built in mail server so I can receive messages when the terminal is powered off. This is interesting, but it’s nothing new.

  3. @somethink – Of course this isn’t new, it run’s a 35 year old operating system!! I still actually have a cp/m system (a Kaypr 2’84), and it is surprisingly usable.

  4. Wow. Nice to see that doing something that tens of thousands of others have done is noteworthy!

    Call me when they do moon bounce digital communications on this thing. THEN I’ll be front page hack-a-day impressed.

  5. 900HMz radio links good for a few miles have been out for a while now (I used a few older more expensive ones in my gps trackers http://www.krazerlasers.com/gps/ the maxstream xtend is good for over 10km miles line of sight with ruber duck antennas at 9600baud), and they have been really cheep for about a year now. check out the radiotronix wi.232 http://www.radiotronix.com/products/proddb.asp?ProdID=195 which is supposed to be good for about 5km line of sight (although I have not had a chance to test them yet)

  6. CP/M? Does this mean that it runs those nifty programs that where available for the C=128 back in the day? If so, and if it could hold a SD card, it could mean that all the library of programs could be there. Tres cool!

    For the youngsters amongst us: CP/M is the program that Microsoft reverse engineered to create MS-DOS.

  7. Microsoft didn’t reversed engineered cp/m. First of all they didn’t even write DOS, they bought it from a guy that some says he reverse engineered the CP/M code, and some that he writed DOS from zero being based on cp/m.

    BTW, the 3km Wireless link isn’t that impressive, it’s just a 433MHz module with a little antenna.
    You can even use a Yaesu handy connected to your computer RS232 port and make the most easy 5km wireless link.

  8. I’d love to have this thing in my car, WITH the wireless connection, but i want to see some way to interface this onto a cell network as well (Maybe bluetooth?) this would be great for email updates while i’m on the road, or using as a twitter box. Also, i’m assuming this is running linux, what about a 32GB or 64GB SSD and mplayer on it? is it powerful enough to decode MP3’s? would it be possible to engineer that (everything’s possible, but does the hardware allow it)??

  9. Yikes, I’d better reply to a few of these!

    1) Solar is where this is heading. This started off as a simple picaxe repeater http://www.picaxe.orconhosting.net.nz/all3.jpg but when you get 10 nodes and they are all talking on the same frequency you get data clashes. And the software to handle that ends up too big to fit in a picaxe. And then you need to update the program out in the field on 10 nodes, and that takes ages, and so you need a system that can automatically transfer updates through the wireless system. I think CP/M is the simplest operating system that can do this, but xbee might be able to, and perhaps there are others. I want to send “real” data through the network, eg have a PC take a picture and turn it into a .jpg and send that jpg through multiple nodes and have it come out the other end. Without having to pay a mobile phone company for the prvilige.

    2) Anyone interested in building one, come and join the N8VEM open source project http://groups.google.com.au/group/n8vem This stuff is not that simple, and a full description runs to many pages (in fact to a whole separate website http://n8vem-sbc.pbwiki.com/ ). It didn’t exist only a few months ago, but the bit that I like is that everything is open source and nothing is tied to a single source or manufacturer and that many people are contributing.

    3) Cost of 145 – oops, yes that should be US$145.

    4) The range depends on which module and how high the antenna is, but the major factor is the super senstivity of the receiver. This enables the transmitter power to be kept low which conserves battery power and keeps the authorities happy. A yagi boosts the range even further http://www.yishi.net.cn/product_detail.asp?id=53&fid=171

    5) RF modules are at http://www.yishi.net.cn/index.asp?id=47

    6) Kantronics KPC? I’ve just checked that out and it looks sweet. I reckon we could interface to that…

    7) Re “Call me when they do moon bounce digital communications on this thing”. Yea, I know it doesn’t look so impressive on a bench. The aim is to leave off the VGA display and have these things out in the field doing things like measuring tank levels and opening gates and turning on pumps, and do it all with solar power. But it has enough smarts to handle the packet system for the transponder on the space station and just needs a radio with enough power (and ?a ham license) http://www.rac.ca/ariss/arispak2.htm

    8) Yes it can run your C128 programs.

    9) The history of CP/M is fascinating. DIR is both a DOS and CP/M command.

    10) This isn’t linux but if you know how to use any text based operating system it is pretty easy to learn as there are only about 10 commands used commonly in cp/m. DIR for directory, ERA to erase a file, TYPE to type a text file on the screen, PIP to do file copy, and type the name of a file to run it. Simple versions of many popular languages are available too, like Basic and C.

    11) I don’t know about decoding an MP3. Ipods are so cheap though.

    12) Yes SD mass storage is on the “to do” list. Indeed, the next thing on the list is to take the whole project and fit it into a single 40 pin Propeller chip.

  10. Hi! Thank you for the nice article! The N8VEM home brew computing project is open to anyone who would like to build their own home brew computer. There are lots of PCBs available for various projects like this one. There is a Z80 CP/M SBC, ECB backplane, ECB bus monitor, ECB prototyping board, and Disk IO (IDE and FDC) available now.

    Soon a Zilog Peripherals (CTC, DART, dual PIO) board will be available and after that a 6809 host processor. N8VEM builders are making their own stuff too which is a lot of fun. If you would like to build your own Z80 computer stop on by we are always looking for hobbyists to come build their own peripherals and contribute back.

    There are bunch of related projects too like the PockeTerm and mini-N8VEM and other things too.

    Thanks and have a nice day!

    Andrew Lynch, 73 de N8VEM

  11. Mr X – how small do you want to go?

    Leave out the vga monitor? Well 20×4 LCD is certainly good enough for simple input and output especially if you write code to ask questions one input at a time. I’ve got 3 on my bench at the moment for wireless testing and they don’t need the big vga screen for what I am testing.

    Not sure the LCD can be shrunk much more.

    The entire N8VEM board may well end up being shrunk into the 40 propeller board on the right. Log into the propeller discussion forum as this is being actively discussed.

    And the prop chip comes in much smaller packages.

    It certainly is going to get smaller. Your input would be most appreciated.

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