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Best avenue for prototyping with CC2520 and MSP430AFE251

Ken Steele
Prodigy 185 points
Other Parts Discussed in Thread: MSP430AFE251, CC2520, Z-STACK, MSP430F2013, CC2530, REMOTI, MSP430F2618, MSP430F5438

To all concerned:

I'm working a project requiring a large ZigBee mesh network, of which each node requires a delta-sigma ADC (minimum 16-bit) to do its task.  I've been able to rough out the ADC interface using a MSP430F2013 and a LaunchPad, but there's not nearly enough memory for a Z-stack.  My thought is to use a MSP430AFE251, as it includes an SD24 and lots of memory, paired with a CC2520 for the wireless. (Part cost is key, so while I could pair the '2530 with an ADC, the cost is greater than the '251/'2520 solution.)  The next step in my development is to rough out the network stuff, to include using signal strength as a way to let the network physically self-actualize node locations (relative to one another).  I'm trying to minimize the outlay of cash, and am weighing two options.  One, use the CC2530 development modules to rough out the network stuff, and assume the '251 will handle the rest.  Two, use the CC2520 development modules, but wire them to a 24-pin socket target board with the '251, and thus effectively prototype the end product.  The former is relatively inexpensive for a two node kit, but the latter could get pricey, especially as it needs a programmer to go with the target board.  Therefore, I suppose I have two questions:

1) Does the '251 have enough memory to run the Z-stack when paired with a '2520? I've read through a lot of documentation, and "required memory" doesn't seem to come up in the discussion.

2) Any recommendations on cost-effective prototyping, assuming the answer to #1 is yes?  Method A, B or a better alternative?

Thanks in advance for any guidance anyone can offer.

--Ken

 

  • 0
    Guru 227245 points

    I can't say anything about the Z-stack, but about prototyping, well...

    It's not the worst idea to put the RF part into a separate module. Depending on your target market, it might be necessary to certify teh RF part for compliance with different local rules and restrictions. Having a module that is certified once, allows for layout changes in the main product, or even re-using the module in different products, without need to re-certify every new revision. Depending on the applicaton, it definitely makes up for the slightly increased cost of having two separate PCBs. It also may reduce the losses on failed boards during mass production, since both can be tested and discarded separately.

    However, this doesn't help you much with the CC2530 vs. CC2520 decision. But some thought on this too...

    The 2530 includes a processor that is capable of managing the whole Z-stack stuff. This is convenient when your applicaiton is 100% satisfied with the default protocols. You don't have to bother with any low-level stuff Depending on number of future units to build, the additional cost may well be balanced by the reduced development time.
    However, if you're going to do things that are a bit besides the default operation, then directly controlling the transceiver by the MSP is the better solution, as any change can be applied on the MSP side and doesn't require changes on the 8051 firmware in the CC2530.
    After all, it depends on the applicaiton and there is no general answer.

    About memory requirements of Z-stack, well, the CC2530 description seems to indicate that Z-stack requires the CC2530F256 (the description for the RemoTI application instead says "F64 and up", so it seems the F256 is indeed minimum requirement)
    Not the MSP is somewhat more efficient in code size than the 8051 core, but it will give you a hint about Z-stack code size. All CC2530 have 8k of ram, and if this is sufficient on the 8051, I don't think that you'll need more on the MSP. Likely (much) less is required but as these are only clues, not facts, I cannot say what the minimum requirement is.

    However, the 16k flash and 512 bytes ram of the AFE251 are most likely much below the requirements for running Z-stack on it. The Z_stack software is available in versions for the MSP430F5438 (256k flash/16k ram) and the MSP430F2618 (116k flash/8k ram).

    Uh, looks like had an answer to question #1 as well :)

  • 0 in reply to Jens-Michael Gross
    Prodigy 185 points

    Jens-Michael:

    Very helpful, thank you.  Your Z-stack-memory-assessment-by-comparison is well reasoned, and I'll be looking at those downloads shortly.  Separating the RF is not as critical for this application, which has a very short transmission distance; still, good input, and appreciated.

    --KenS
     

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