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CC3100MOD Questions

Klaus Allmendinger
Prodigy 60 points
Other Parts Discussed in Thread: CC3100MOD, CC3100, CC3100BOOST

Hi,

I am planning to use the CC3100MOD part in a new design. As I understand, it is pre-certified. I have the following questions regarding the use of the CC3100MOD:

1. In my design I cannot use an on-board antenna (device will be mounted in RF-opaque metal box). Instead, the BG-RF pad of the module will be connected to a board-edge SMA connector (50 Ohm), connected via 1ft coax cable (50 Ohm) to a duck antenna (50 Ohm). As the trace length between BG-RF and SMA connector is only ~1.6mm, do I need an impedance matching circuit? IMHO the additional trace lengths required for the impedance matching circuit might actually be themselves the cause for needing it in the first place.

2. Does the TI WIFI certifications only apply if a board mounted antenna is used, or does it apply also if the antenna used does not have a higher gain than the board-mounted chip antenna?

3. Does the CC3100MOD part come pre-flashed with a (preferably latest) service pack?

4. In my design I have a spare UART in the main MCU (ATMEL SAMS70) that could be used for the format flash function of the CC3100MOD for field upgrades. However, I cannot provide an exact baud rate of 921600. The nearest I can provide is 937500, which is 1.7% faster. Is this within spec for the CC3100?

5. The CC3100MOD datasheet only mentions to provide ground vias under the module for thermal reasons. Is there a spec on how many are needed for thermal reasons? I do have a solid ground pad under the module. Do I need to provide for thermal conductance to the back of my PCB?

Additional note:

The Production line guides for CC3100MOD and CC3100 have a drawing for how to connect a CC31XXEMOBOOST board to either a CC3100QFN or CC3100MOD TX/RX. Specifically it says to connect P1.3 to UART-RX of the CC3100(MOD) and P1.4 to UART-TX. However, the schematic of CC3100BOOST Rev4 shows P1.3 to be connected to UART-TX of the CC3100 and P1.4 connected to UART-RX of the CC3100. I verified the schematic to be correct. Therefore the production line guides are both wrong. In addition, the production line guides do not show a ground reference connection (P3.2). Without that using the described procedure does not work.

  • TI__Guru* 91206 points

    Klaus -
    1&2 - Wi-Fi certification has nothing to do with the antenna - it has to do with the operation of the device., regulatory certification on the other hand does have to do with the antenna gain and type used. Your point about the 10pF out to connector...you are correct - this just moves us around a little back to 50 Ohm point, at frequency. if you use an antenna of higher gain than what used in our testing, then you need to check that the resulting EIRP does not violate the rules in the region you are operating / and later selling in. Keep in mind the US allows much more power out in this band than the EU does.

    3. Yes
    4. not sure about this one - i will have to ask the design guys - i see your point though - the documentation on this detail is not the best. I would say that you most likely could get by with 115200 8N1.

    5. not 100% sure on this one - i will have to check and get back on this one too. we need to spruce up the docs on this topic - i see alot of lack of follow through on details - will work on that.

    6. I kind of agree with you here, we should put VCC and GND on any wiring diagram (where its appropriate) and not assume the user is clairvoyant.

    will get back to you on these still open items early next week.

  • in reply to Josh Wyatt
    Prodigy 60 points

    Thanks for the fast response Josh.

    Re.1:

    The duck antenna is basically just a 1/4 Lambda antenna. So it probably has less gain than the chip antenna, but is more omnidirectional. Initially the product will be mostly US and later EU. For reduced TX-power in EU mode I should be able to program that in the module using the API.

    Looking forward to the answers to the unanswered questions.