Precision Mixed-Signal MCUs vs Peripherals on AVR platform

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#1
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Hi,

I read this month's '51 update article in Circuit Cellar and was impressed with comments regarding Silicon Labs Precision Mixed-Signal 8051 MCUs.

http://tinyurl.com/4c8bk

I cut my teeth on the AVR RISC core, and wonder if I should continue to hang peripheral devices on the AVR or go to the '51 Precision Mixed-Signal 8051 MCUs for the simple fact that 24 bit ADCs and DACs on the same chunk of silicon is quite compelling. In order to do so, I will require new dev software and boards.

Most of my work is with interfacing some sort of analog transducer.

I know this is like asking you what car I should buy, but I was hoping to generate some dialog on the matter.

Thank you for your insight
Regards,
Patrick

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Hi Patrick,

for me the decision is quite simple:
I need devices that work with 5V Vcc to get simpler designs(i.e. some sensors only work at 5V and interfacing them is much easier then).
Second point is the price. The silabs chips range from about 5 $ for the smallest chips to more than 50 $ for the big ones(all prices for single quantities).
If you're doing just prototypes or very small quantity projects, those 25 or 50 $ you spent for the chip is the price for a prototype PCB, completely populated with AVR and peripherals.
And if you don't need high speed designs or the complete set of onboard peripherals, most things could be done for less money using an AVR and, in some cases, external peripherals.

My last project was a sensor interface for a sort of inertial measurement unit. Due to the project guidelines I had to use at least 12 bit A/Ds and a CAN-interface for connecting to the PC. All the sensors are only working at 5V and space was really limited. With all those requirements, my decision for the AT90CAN128 in QFN package was quite simple. It works with 5V, SPI-A/D-Converters are easily interfaced and it has onchip CAN interface.
If I had to make a 3.3V design instead, maybe I would have chosen a silabs 8051 or an analog devices ARM7.

Best regards,
Christian

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The look pretty cute but also seem to be pretty expensive. I just migrated
a small portable instrument from the At89c4051 (using an external dac and adc)
to the Mega88 eliminating 5 ics in the process and reducing the cost about 30%!
Using the cheapest SL part would have increased the cost about 15%. I look
at everything on a case by case basis, but from a cost standpoint it appears
you can do better by selecting external analog parts as needed and hooking them
to an Avr. On the other hand, if one is building general or semi-general
purpose systems to meet random customer requirements, these things could
fit pretty nice. Might have to get on to at least play with, and I like the crossbar
switch scheme to assign special functions to the port pins.

Tom Pappano
Tulsa, Oklahoma

Tom Pappano
Tulsa, Oklahoma