Can anybody give me advice on capturing a raw binary data stream into a PC?
I'm working on a project to develop an instrumentation receiver for monitoring signal strength from a number of remote transmitters. The front end (tuner, mixer, digitizer, etc.) is working pretty well, but the next step is giving me trouble. I will be shifting out data from an A/D converter, and need to get it into a PC somehow, time tag each sample, store records in a logging file and every few days read the accumulated stuff out from a host computer (FTP or Telnet over the Internet, I'm thinking). There will be several of these data-gathering stations operating unattended, spread out over several miles. Data files should be no more than a few Mbytes.
I thought this would be straightforward, but I can't come up with a simple way to handle the PC interface. Is it really so difficult to do this, or am I missing something? I hope it's the latter, and somebody here can point me in the right direction.
I'm more a hardware guy than a programmer, so I'm looking for something simple.
That was my suggestion. Best bet would be to format it in ASCII, perhaps in a comma-delimited format that could be directly imported into Excel or compatible programs.
This would be easy to do with just about any micro controller -- a PIC or an 8051 would be the most likely choices.
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Right. I was thinking along those lines myself. The real sticky part for me is how to manipulate the bytes in the PC environment. What software packages do people use to organize RS-232 inputs into records, files, etc. complete with time tags? Power Basic, C and Python have all been suggested to me, but none with any conviction.
Also (secondary consideration), I was wondering if it's wise to rely on conventional serial and/or parallel ports to be around in several years. I would like this project to have a fairly long life, and I can foresee having to replace components (like laptop computers) as time goes by. Other, less knowledgeable folks may be running things eventually.
I don't know what else you may expect to be around. RS-232 serial ASCII is about the most common computer connection that has ever been around. It has been used, as far as I know, by about every computer company in history. Although some (laptop) computers today come without COM ports, you can always get some plug-in card to provide it.
Depending on your budget, you may consider a digital I/O card which is connected to the A/D converter directly. These cards are available in several varieties (USB, PCI, PCMCIA). These cards usually come with their own API which is (usually) easy to deal with.
I think this is the shortest route. You'll have the data inside the PC without having to develop another 'in between' device and debugging a PC application is much easier than software in a microcontroller.
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It's not difficult to write some software in C or any other suitable programming language that reads data from the PC serial port and outputs it to a file, with time/date stamps. I'd do it from DOS with a program written in gcc.
Could you link them to a wifi wireless network? dumping data directly to the remote shared harddisk? You might have to ask a LINUX guru ,because the number of open shares in XP might be limited. The range ,when using directional arials might be several miles.(according to a thread a few days ago).
csv (comma separated value) files can be imported into excel, these are just ascii comma delimited files. A vb written program can pick the data from your serial port and place it into the excel spreadsheet. If you need graphs larger than excel's limited 64K, have a look at
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for around $30 it's a great deal - i've been using it for all my data acquisitions for several years now. As far as the fate of serial ports, I have the same concerns. there are several serial to USB dongles out there that claim to be "virtual" serial ports on the pc. I plan to look into Microchips PIC, they have USB & USART's built in. Good luck...
With 100% conviction I'd suggest that PowerBasic. Suspect the needed time stamped log file program would take a whopping 10 lines or so. I'd stick with RS232. It has a massive, diverse user base (=money to be made)hence will receive continued support. In the meanwhile other comms fluff will no doubt come and go. john
I read that some of these rs232-usb dongles don't adhere to standards properly in way that makes them troublesome. Otoh, with PIC one can run the show oneself ;)
buy a USB-cellphon cable (I use the Samsung E700). Cut the Plug and use the cables directly to power my µC from USB and habe a UART with 3V3 Level. What do we need more? Yes a 5V to 3V3 LDO and a few caps.
I've heard a lot of good things about Powerbasic, and I may go that way. It's inexpensive, seems well-established and has all the capability I need for this job. Something one could base a project on with some confidence!
Yes. I was thinking of one of the Microchip PIC family with USB capability. But if the budget can take it, I can just use a commercial data acq module for each site. DataIO, Dataq, Onset and others all make units that should do.
Haven't used Perl, but I've heard about it for years. What's it like? Isn't it basically a scripting language?
Field strength measurements multiplexed over 3-5 channels. Sample rate will be about 1/minute, with
Mcu: AVR, PIC Nic: RTL8019 (Asfair realtek have some nic that does 8-bit) And you need "magnetics" aswell.
Another option is a mobilephone + mcu. As most mobiles talk serial in some way or another. (ex SE CDU-11 datacable is a rs232-usb adapter in reality asfaik).
It's a mix between shellscript and C languagewise. But it's nice because it allows you to glue together programs. And let's you concentrate on your goal. Provided the task is relative small.
Sound like some weather, possible thunder science ;)
I looked into thunder detectors when I worried it would blow up something ;)
(2x aerial -> amplifier -> soundcard or real 200 kHz adc, then triangulation :)
RS-232, by far, is the easiest way to go on a PC, and frankly, you really don't have any alternatives.
USB is not what people often think - you can't just whip up some code to talk to a USB port on a PC. The plug and play facility is misleading - to talk to a raw USB port requires considerable skill in driver-level development, because, techncially, USB hardware requires device drivers to present an interface inside the kernel, upon which other device drivers ride, and finally, the kernel presents a user-level interface that you can program against using your favorite language such as C or BASIC. So if the USB device is a digital camera, the interface that at the user coding level will see something that expects to behave like a digital camera. If you just want to send bytes back and forth as you would for RS-232, forget it, you will suffer, unless you are using a configuration that mimics an RS-232 serial port, but at that point you might as well use a real serial port. (This is slightly not true but...).
So with RS-232, I would do this:
Connect modems on each remote module's serial port. Connect modem to central computers serial port. Since distance is so far, use conventional external modems with POTS. If distance were shorter, you could use cold cable with no dial tone and it would still work.
Pick your favorite compiler. Microsft has done a stellar job in creating these free compilers:
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My favorite is C/C++. You probably want the one for BASIC.
Here's steps in C. There wiill be direct analogs in BASIC, because all the BASIC API's in Windows do is simply call the underlying system API's (which are written in C).
On central computer, Open serial port- CreateFile()
Set format for transfer 9600-115,200, 8, N, 1, (don't remember function).
Dial out ATDT+1 617 555-1212 pause to allow connnection - WriteFile().
Open a data file - CreateFile() again
Read byte or bytes from port - ReadFile()
Call system function to get time for each record - GetSystemTime()
Write collected record with time stamp into data file - WriteFile()
After finished, close data file - CloseHandle().
Close serial port - CloseHandlle() again
Store records in format of your choice, like CSV, etc. Note that there is no "magic" to formats. Pretty pictures won't automatically jump up on the screen just from choosing a format. Human beings must give semantics and detailed instructions on what to do with the data before anything fancy happens.
Use Hyperterminal to test your embedded module before you write your central-PC application by typing commands directly from Hyperterminal, through cable, to the module (which means u will need ASCII command set).
This is a very enlightening discussion and I thank you for the pithy project outline. I hadn't thought how useful Hyperterminal might be as a debugging tool, until you mentioned it. Good one!
My job will be done once I get everything into a standard file format (CSV, probably). Somebody else will worry about making the pretty pictures for reports and presentations.
My regards to everyone who has chimed in here. I appreciate the help.
I recommend to stay away from PIC processors. Been there, will never go there again. Too cumbersome to program and way too sensitive to static discharge.
A TI MSP430F149 uC and a CP2102 USB tot serial chip (from Silabs) make a nice and simple combo.
The adavantage of the MSP430 series is that you don't need a programmer to program them. They can be programmed directly using the serial port. Software can be written in C using a GCC compiler (look for mspgcc).
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