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need advice on microcontroller selection

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New Member
I need some advice on which type of micro would be best for an application I already have prototyped. The idea is to give the application some internal smarts and possibly an alternative to a Parallel printer port interface, while keeping some real speed in the process.

Some background on the device is in order. The device is basically an addressable parallel expansion device. By itself, it has no other purpose than to move large amounts of data back and forth from a single 8 bit port on one side to many 8 bit ports on the other side, kind of like a MUX-DEMUX unit. The idea is to use a PC to access and control multiple devices, of different flavors, on a time-shared basis. Typical uses would be data acquisition, and remote control systems.
Currently the prortotype runs off an EPP printer port which controlls the entire device. Although it wooks superbly, and can transfer data at rates approaching 4 mega-bits/second, all data and control is currently being pushed thru the printer port. A typical data cycle might be something like this:
1. PC supplies end address to be read or written
2. PC supplies data to be written (if applicable)
3. PC generates read or write command
4. PC reads data returned (if applicable)
The entire process could be sped up immensely, if the controller was a smart device and could initiate simple end port reads & writes autonomously, then only use the PC communications channel for control information or data update passing. It could also allow some form of data compression to be employed.
What I THINK I will need from the micro, is
1. On the device side; the ability to output an 8 bit address for decoding, and 8 bit bi-directional data bus, and a few miscellaneous gating control & timing leads, Ideally 3- 8 bit parallel data ports would suffice. Additionally it needs to be able to have a ram table of around 2-4K bytes or more.
2. On the PC side; It needs to be able to either interface a fast parallel printer port or, preferrably, a USB2.0 port
3.. Micro device needs to be capable of reading or writing any port at a rate of around 250-500ns. so it would need to be fast enough to do this plus its internal programming overhead.

Now, I see no need to reinvent the wheel here, and have seen the dongle type USB to Parallel port devices, so this may be an option to consider. Possibly by using one of these, I could keep the applications device totally parallel in nature.

Anyone have some suggestions I could take a look at that may fit the bill?


Hi, you have written too mutch for nothing i guess, can you resume all that ? Anyway there are some new pic's the 18F4550 that run at 48Mhz and also have USB interface, that is speed enough for your project ? You may also try AVR's, to work with the parallel port you don't need much because it's slow. Anyway pic is easyer to develop with, well, it has few instructions, in otherhand if you want many instructions try the AVR, these 2 are the most known and cheap to use, there are others like the "usual" 8015 and it's designs, MaxQ2000 actually it's very very very fast but it's 16bits, ... :lol: what is your doubth ??? there are so many and your aplications seems simple enough for each one :? .

I hope i had brought any light upon you :lol: , bye :D


New Member
Thanks Tiago
The info you provided on the 18F4550 pic looks like it is just what I am looking for. Now I need to study the data sheets in detail and see if I can figure out how to interface and program it. Looks like I have much to learn.
I am sure, once I get into it, I will have MANY more questions.
Thanks again
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