decision about what 'type' of micro to use

[Buriedcode]

Hi, I having real trouble deciding what type of microcontroller to use for my app. Heres the specs:

Read in data from a I2S bus, 32KSps, 20-24 bits.
Encode with FEC and add extra control bits.
Encode with manchester encoding, with preamble and word sync.
Output in serial, or to a DAC for pulse shaping (so we have 8 bits per actual 'bit').
OUtput datarate = 1.526MB/s - 3.072MB/s.

My original design used a simple CPLD, and it worked a treat because its pure logic, but a CPLD lacks the memory/arithmatic for complex forward error correction, pulse shaping (probably using LUTs). Also microcontrollers have many other peripheral goodies I can use to check battery status, and implement controll functions. Also, I reallly don't need that many I/O lines. Ideally a 'one-chip' solution.

A PIC is out, its just not fast enough with 5MIPS, and the faster ones are too big for my design. Maybe an Atmel chip, with 1 instruction per clock. I'm really looking at ARM micros now, maybe even a cheap DSP, since these have the speed, the data-bus width (16 bit) and low power consuption compared with the CPLD.

This was 'sparked' by the recent post about 'ARM' micro's, I did a little research and found some very cheap ones, and some cheap DSP's with ARM architecture.

So, anyone have any thoughts on the matter?

I realise it may seem over-kill, since I'm just using the chip for its speed, (one pin outputing 3mb/s) but I'd like to have room for upgrades, and I've seen similar devices (wireless digital audio) that use fast microcontrollers instead of DSP's (I'm not doing any audio compression btw). And finally, for some reason some quite powerful micro's are in fact cheaper than basic CPLD's (in the UK anyway), so cost is a factor.

Sorry for rambling on, but I'd like people's experiences with fast microcontrollers, and what their opinion is as too where they would fit in, in such an application.

Thankyou

Buriedcode.

 

[IanP]

As far as speed is concerned have a look at Silicon Laboratries.

Silicon Laboratories C8051Fxxx family of 8051 mixed-signal microcontrollers integrates world-class analog, a high-speed pipelined 8051 CPU, ISP Flash Memory, and on-chip JTAG based debug in each device. The combination of configurable high-performance analog, 100 MIPS 8051 core and in-system field programmability provides the user with complete design flexibility, improved time-to-market, superior system performance and greater end product differentiation.

Try
https://www.silabs.com/tgwWebApp/ap...ontent/products/Microcontrollers/en/index.htm
You will have to sign-up but it is harmless..

 

[Buriedcode]

hey, thanks for your swift reply!

I signed up and it looks pretty sweet, I sohuld have used the 'Embedded Applications' phrase in google, since thats what this design really is. But I'm limited by what I can buy, I can only order from farnell, or RS (RS has nothing). I usually find I chip I want and find a close match from distributors, the reason I mentioned ARM micros/dsps, farnell has loads.

I'm not simply trying to replace a CPLD's job, just seeing if there are any cheap micro's out there that can do the same job, but with added features and versitility. Luckily, the hard part of most forward error correction is in the decoding, which will be in my receiver, no limits on power and size, so finding a chip for that is easy. The portable transmitter chip is another issue.

My ADC is external, and few micro's have sigma delta ADC's on board, with this resolution and speed, plus I already have it Maybe ARM micro's are just not suited for real-time digital audio transfer. I'll keep searching, hopefully one will have a I2S peripheral hardwired.

Thanks again, and sorry if this is post is pointless, I just can't decide what to do next, plus I prefer working with micro's, and thier memory allows for better algorithms than a CPLD.

Buriedcode

 

[bobcat1]

Hello

Use the philips ARM7s microcontroller LPC21xx is the best soulation to your project since it can provide processing speed I2C ,A/D,Memory etc all on a single chip

You can also consider 2nd sources like the ADm7xxx from ANALOG,TMS470 from TI SAM7 from atmel and STAR7 from ST all based on the ARM7S core

All the best

Bobi

 

[Buriedcode]

Hey bobcat1,

I spent a good hour skimming over the datasheets for all the chips you mentioned. I'm so behind in current technology, those devices are very cheap for what they are, and although I tihnk they're a bit 'over kill' for the transmitter in my project, the philips LPC21xx are ideal(!) for my receiver. Since this not only deals with audio but also a LCD interface, input buttons, and general control of everything on the board, which I suppose it what they are designed for It seems that with the ARM core and perihperals such as the hardware multiplier, we're getting ever closer to a DSP type thing, but more versitile, and again, cheaper!

Thanks a lot man, looks like I'll be using one of these MIPS beasts in my next project as well!

Thanks again.

Buriedcode