Serial to Parallel Convertor Circuit 1

[syset]

Hi,

I am looking to construct a serial to parallel convertion circuit. Will be taking differential signals CLK, and DATA, at 2.5MHz. What is the best solution to convert these data streams to 32bit parallel data? PIC? FPGA?

Thanks!

SET

 

[Skogsgurra]

At a 2.5 MHz clock, you have 400 nanoseconds to handle it all. That's precious little time. Many micros have I2C and SPP and similar interfaces built in. They may be configurable to do the job directly - or not.

I would reach for my work-horse; the LPC 2106 ARM processor. It can read a seriel data stream directly, it has enough power and can output a 32 bit word directly. I would not use FPGA if I weren't familiar with the technology beforehand.

I guess that a reasonably fast PIC could also do it. Even if a suitable serial interface isn't available.

Does the spec require that you finish the outputting after you have received the 32 bits and before the next clock arrives? That is the tough part of it. If that were relaxed, your choice will be broadened.

Gunnar Englund

http://www.gke.org

 

[itsmoked]

Hi syset, skogs;

If you go the PIC route you can use one of the PIC24 series. If your data is 8 or sixteen bits you could do it handily. Since the 2 built-in SPI interfaces chow down on 8 or 16 bit stuff. Also the SPI units have 8 byte FIFOs which gives you a lot of breathing room. The part runs an instruction every 100nS. So you could easily pull and stuff the data onto various data ports and then gate it out with another pin or two.

The 24 series is one of the DSP processors with the barrel shifters yanked.

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[syset]

Hi guys,

Thanks for your valuable advice. Appreciate that.

Since you all think that it is not advisible to start with the FPGA. I will look for other option for this application.

I have clock signal at 2.5MHz (differential signal) and the data (differential as well) comes in 34khz packets. Each packet contains 32bit data and a start bit. I will have to detect the start bit and then read the following 32bit data and output it in 32bit parallel single-ended TTL signals. timing is quite relax, as the 32bit parallel signal is output in 34khz rate, perhaps with a clock signal accompanying that as well.

Skogs, the ARM processor you suggested seems pretty cool. Can you point me to the right place to get hold of the device, development board, and getting started info. I would to get this working in a short time. Will appreciate all your inputs.

Keith, do you think the PIC 24 could handle 32 bit output? Or are there any other PICs which may do it?

Thanks again

syset

 

[itsmoked]

Before I comment further I am a little confused on the details.. 2.5MHz but at 34kHz packets? I don't understand.

Are you saying these 32 bit packets come every 0.29uS?

You are to receive these serial packets and then present them as 32 bit words?

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[syset]

Yes Keith,

The start bit and subsequent 32 bit data comes in sync with the 2.5MHz clock. But these 32 bit data packets comes only once in a while, at 34k packets a second rate. The rest of the blank time, the data line just goes high-impedance.I have got to find a way to detect the start bit as well (which is a high-to-low transition in the beginning, before a burst of 32 bit data follows). Differential signals are a little of a pain to work with.

syset