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Single chip solution or multiple chips?

Matt Staniszewski
Intellectual 360 points
Other Parts Discussed in Thread: CC1101

Hi everyone,

I'm working on a design that requires a MCU, transceiver and Ethernet controller to take data sent through a network and transmit it to a sister board via RF.  I'm very interested in TI's CC430, as I've used the MSP430 family and CC1101 before, so I'm seriously considering using that for my project.  However, I realized that it doesn't have Ethernet support, so I'd need another chip.  I've read up on a lot of single chip solutions as well as using multiple chips, and depending on factors such as number of I/Os and cost, there are a variety of options available.  

As I see it, there are three possible routes I could go

1) MCU + RF chip + Ethernet controller

2) MCU w/ Ethernet + RF chip

3) MCU w/ RF + Ethernet controller

I wanted to hear people's experiences with these combinations and if they have any recommendations.  I'd really appreciate any insight, as there are so many options.

Thanks!

Matt

  • 0
    Guru 12160 points

    Hi Matt,

    If you are concerned about cost, then you probably should go with an MCU with built-in ethernet. There are plenty of "cheap" Cortex-M3 devices out there with built-in ethernet.  The Stellaris line from TI is an example, and they even have MAC and PHY integrated into the MCU.

    Then find an RF transceiver that suits your needs precisely.  There are lots of these around too, with lots of competition, and lots of resources, so you can save money here too.  The I/O between the transceiver and the MCU is naturally less intensive, so having it off chip is a good fit.  Also since you've used CC1101 before you can stick with that family and re-use all your knowledge there.

    The added bonus is that the ethernet controller is a high data rate device, and having it built into the MCU means you can take advantage of faster I/O between the CPU and the ethernet controller and probably use DMA too.  The network and the remote peer will thank you.

    Jeff

  • 0 in reply to Jeff Tenney
    Guru 35565 points

    Jeff Tenney said:
    There are plenty of "cheap" Cortex-M3 devices out there with built-in ethernet.

    I think you'll find that most of them need an external PHY chip?

    If Stellaris isn't still unique in having on-chip PHY, it's certainly the exception rather than the rule!

     

  • 0 in reply to Andy Neil
    Intellectual 360 points

    Hi Andy and Jeff,

    Thanks for the tips.  Yea, I realized after doing some more searching that there aren't really a lot of low cost ethernet controllers that include the support I find on integrated MCUs, and with the non-stock issues with a lot of the RF integrated MCUs, I agree that a MCU with integrated Ethernet support is the way to go.

    Andy, you make a good point about PHYs.  I downloaded a bunch of specs to sort through, and I'll be sure to check on the PHY; I had assumed most had it included.

    Thanks again!

    Matt

  • 0 in reply to Matt Staniszewski
    Intellectual 360 points

    Ok, these are the two sets I've narrowed it down to:

    1) Microchip route: PIC18F97J60 (MCU w/ Ethernet) + MRF49XA (Transceiver)

    2) TI route: LM3S6618 (MCU w/ Ethernet) + CC1101 (Transceiver)

    Based on pricing from Digikey, the TI set of parts will run me about twice as much, which may not work out in the long run if we mass-produce this design.  After doing a spec comparison, I think I may run with the Micro set of components since I don't need as much power as the TI offers.  If there's anything else I'm overlooking, I'm open to suggestions.

    Thanks!

    Matt

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