Help for MCU/DSP selection

Greetings all,

Been lurking this newsgroup for a while and I'm rather impressed with the quality of the discussions over here so I thought I'd run a question by y'all.

I have a project where I need to upgrade an existing design. The unit is a medium frequency power converter (25-50kHz) that currently runs off two dedicated PIC micros. The new specs require for increased signal processing and thus I'm looking at all sort of design options, and quite frankly, the newbie that I am is almost feeling overwhelmed by all the options out there.

Here's an overview of what I need to accomplish.

Signal processing of a 25-50kHz signal with limited accuracy (10 bits ADC OK) for RMS, enveloppe, dI/dT and other such measurements. Rapid, real-time signal detection and processing (gate driving mostly)under 1uSec for zero crossing, peak values and anomalies. (>1.5 MSPS). SPI, CAN (optional) and USART interfaces for embedded hardware and external communications. (Ethernet a bonus but not mandatory) Basic processing for PID and other control / monitoring logic. Enough processing for FIR/IIR filters and math processing (nothing very complex though). The application is moderately cost-sensitive (

Reply to
Flash01
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"Flash01" wrote in news:1JadnQS5wqOHGWrVnZ2dnUVZ snipped-for-privacy@giganews.com:

Hello, You didn't mention if you were willing to live with fixed point or floating point processors, if that matters. But it looks like you are focusing on 32-bit machines anyhow, which eliminates one nice little processor I've recently worked with (16-bit) which is the Freescale

56F83xx part. It doesn't have E-net either, but is quite cost effective and has alot of on board peripherals and ADC, etc. Of the ARM-based machines I am also most interested in the Atmel ARM7 and ARM9 parts, but do not have enough direct experience with them yet to recommend them over ST and others..

Mike

Reply to
Michael Fugere

NXP have released info on 100Mhz Cortex and 125MHz ARM9 models, but if you need 1.5MSPS ADCs that pretty much moves you to TI's devices, so choose one of the newer C2000 family ?.

-jg

Reply to
Jim Granville

"Flash01" skrev i meddelandet news:1JadnQS5wqOHGWrVnZ2dnUVZ snipped-for-privacy@giganews.com...

The AT32UC3C will have a 1,5 MSpl 12 bit ADC, CAN, SPI (but not Ethernet), but it wont be sampling until early next year.

It should be considerably faster than competing RISC processors for many DSP applications due to its

  • single cycle load/store instruction,
  • capable of two samples/coefficients per load/store
  • Single cycle Multiply Accumulate One extra cycle will be added at the end of a sum of vectors. Doing 16 MACs thus takes 17 clocks.
  • Support for saturation

True DSPs with H/W for parallel load of sample/coefficients will still be faster on the DSP heavy stuff though.

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Reply to
Ulf Samuelsson

I would suggest the TI F2811 been using it with good success, only down side for me is the size.. 128 quad flat pack.. other than that it's real easy to use and the TI dsp/bios code composer tools work ok.. Interrupt response at 100 MHZ cpu clock is approx 320 nano secs to ISR execution.. take a look..

Reply to
Thedoc

What packages does this come in ?

What Timing resolutions ?

The TI Piccolo DSPs spec 4.5MSPS, 12bADC and an impressive 150ps PWM timing resolution. Also has 32 bit Quad and 32bit capture. I cannot locate the resolution of the eCAP capture..

Found more info here, on eCAP

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says this The eCAP module described in this guide includes the following features: · 32-bit time base with 10-ns time resolution with a 100-MHz system clock · 4-event time-stamp registers (each 32 bits) · Edge polarity selection for up to four sequenced time-stamp capture events · Interrupt on either of the four events · Single shot capture of up to four event time-stamps · Continuous mode capture of time-stamps in a four-deep circular buffer

So, that looks like it has capture, and a queue to allow adjacent-clock captures (very narrow pulse measurements) It also has a capture prescaler, but only with narrow 5 bit range.. :(

If they had made that a N-tap 2^32 divider, then you could make a reciprocal frequency counter, from one eCAP channel ;)

It's doable with what they have, but needs SW INT scale help..

They start in small TSSOP38/TQFP48 packages

Their lead times look longish tho... Volume production is a year away.... [but there are existing C2000 devices..]

-jg

Reply to
Jim Granville

TQFP 64/100/144. Probably will be BGA as well.

66 MHz device.

Reply to
Ulf Samuelsson

Thanks for the advice guys. I've had a look at most of the stuff you've suggested. I must admit that as far as integration goes, the TI line seems nice. Heard bad things about Code Composer and the design tools however but whether it is true or not I cannot tell.

What about Actel's Fusion lineup? I could definitely use some of the programmable logic these would offer (like a programmable comparator) but I have not read or seen much available on these.

Reply to
Flash01

This looks mighty fine, although the timing (release) might not be right for my application.

Reply to
Flash01

Hey All;

We do similar systems but the software side with complete packaging of most of the options for you. I think there is an article on this that I wrote last year in Real-time Systems. There is better information at:

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and the paper will be linked from there.

Basically, you have really nailed the requirements and constraints to my understanding. I think that the MCHP dsPIC might be good as it has everything that you need. Its there today.

If you add DSPnano you can get all or most of your I/O off the shelf. This would include things like full tcp if you want that.

Other options that you might consider are TI430 although I've not done an implementation on this. It looks sufficient but I/O might be a problem.

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Reply to
rowebots

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