Hello everyone,

I have a synchronous (There is a TX and RX Clock) serial data stream between two old military pieces of equipment. In addition, all the signals are balanced (RS-422). The rate is 2400bps. What I would like to do is manipulate the first few bits of data every time a stream of data comes either in or out. I would prefer something COTS and was thinking of an ARM based industrial controller. I would use the inputs to take in clock and data, process the data, and use the outputs to regenerate the clock and new modified data.

Will an industrial controller Something like a Technologic Systems TS-7580-BOX handle something at 2400bps? Someone suggested a DSP, but I am not aware of any COTS DSP solutions. Will GPIO's be fast enough to handle this task? IS there a different product I need to be looking for?

 

Any modern mircocontroller will handle 2400bps without a sweat, even if you have to resort to using software uarts.
Especially since this is synchronous, all you need is to check for the edge of the clock (i/o pin interrupt will handle that), read the bit, and after you got the whole frame manipulate the data. Thenk you use a timer interrupt to manipulate the output stream pins. That is, if you don't find a processor that can read and write the stream with hardware. If you do, things get a little bit simpler.

 

small Microcontroller such as PIC 16f1503 have hardware USART already. Only one, tough. For 2400 bps, you can easily create the output stream in software.

 

small Microcontroller such as PIC 16f1503 have hardware USART already. Only one, tough. For 2400 bps, you can easily create the output stream in software.

Do they have synchronous usarts? Also remember he needs two usarts.

 

Do they have synchronous usarts? Also remember he needs two usarts.

Yes they have both synchronous and asyncronous serial port. The 16f1503 only has one serial port. Some larger PICs have two serial ports.

The 16f1503 is a 14pin chip, cost about $1

 

Atmel chips are similar for USART pheripherals. I don't know if you can connect RS422 directly, or if you need an interface chip for that as well.

 

RS-422 is a differential bus, so some circuitry will be needed to interface it to standard logic.

 

Thanks for all the great advice. I just learned about the PIC and just found out that some of them contain USARTs vs the standard UART so that is a big plus. I will need to find one that has two ports if possible.

Out of curiosity, how advanced can a program be on a PIC? I am learning that the task at hand might require performing some checksum work and decoding of error correcting computations. I realized that i will need to recalculate the checksum after the modification.

Are there any manufacturers that have a pic ready board or some that are already in enclosures? Perhaps an industrial enclosure?

So from some other posts, it sounds like for 2400bps i could just use gpios if i do not have a usart?

 

As for the 422 i might use a b&b electronics 232 to 422 converter. We are using for a similar issue and they seem to work well.

 

Thanks for all the great advice. I just learned about the PIC and just found out that some of them contain USARTs vs the standard UART so that is a big plus. I will need to find one that has two ports if possible.

Out of curiosity, how advanced can a program be on a PIC? I am learning that the task at hand might require performing some checksum work and decoding of error correcting computations. I realized that i will need to recalculate the checksum after the modification.

Are there any manufacturers that have a pic ready board or some that are already in enclosures? Perhaps an industrial enclosure?

So from some other posts, it sounds like for 2400bps i could just use gpios if i do not have a usart?

Good lord a PIC can handle this without breaking a sweat. Even doing two (or more) "bit banged" serial streams. The PIC18F66J11 has two hardware UARTs and an overload of memory for this application. Maxim (among others) make simple RS-422 level converters.

The hard part will be finding a device already in an enclosure. We're makers here, and can roll these things out no sweat. To *buy* one I would look hard (and email) B&B Electronics who make a broad line of COTS devices and may have something programmable to fit your exact needs.

I not... PM me. That's what I do.

 

Can you pm me? I can not pm yet.

 

ErnieM Can you contact me

I would like to discuss this further. If you could PM me? Your PM is off.