CC3220: Is there any way to interface to an external, non-WiFi, modem?

Hi W1res,

1. Can you further explain what you are wanting to do? Are you wanting the CC3220 to output AT commands that the NWP receives? Why are you wanting the CC3220 to output to an external modem? Would the CC3220 be acting as some kind of a host to the modem?

2. I don't believe there is another MCU that has all the security features you listed, since most of them rely, or go hand-and-hand, with Wi-Fi. MSP432 MCU variants may provide some of the listed security features however (http://www.ti.com/lit/slau697). The CC3120 has these features as well, but would require an additional host MCU.

Please clarify, if you feel I'm missing something about your question.

Best,
Kevin

Hi, thanks for the response!

I'm looking for suggestions for a host MCU. The CC3220 is a WiFi MCU but it has some nice features that seem useful for any IoT application, even if it doesn't use WiFi.

To answer your question #1: I want to send a periodic (once every couple minutes) sensor measurement (a few bytes of data) to Amazon IoT over a cellular module. This requires the following:

1. SSL with support for a client side certificate.
2. MQTT protocol.
3. Secure OTA updates.
4. Some kind of interface to a cellular modem.
5. Some basic security features such as securely storing a device certificate, and preventing malware (unsigned firmware) from being installed.
6. The processing power is trivial for my needs, other than running the internet communications stacks.

At the moment I was considering a ublox LTE module, since they seem to have open pricing and open documentation. I already have the demo kit for the module.

The module has two main options for interfacing with it, both UART only: AT commands, and PPP. AT commands seem very cumbersome and non-standard to deal with, while PPP seems to be integrated into a couple networking stacks already. The ublox device has a built in network stack but it seems to have some bug related to some features I want to use.

To answer your question #2: After making the post I did a search on a lot of MCU manufacturers, and was surprised at the lack of "secure" MCUs. I actually ended up finding the MCP432 and already purchased the demo kit for it.

Hi W1res,

OK, I think I see. So you're mostly interested in the security features the CC3220S offers, but won't necessarily utilize the WiFi?

Will your MCU will be physically connected to the cellular modem? I'm a little confused how 1-3 come into this if so.

If you're interested in learning more about the security features the MSP432 offers, I'd suggest reviewing the relevant documents and then posting on the MSP forum if you still have questions/concerns as I am not an expert on the part.

Best,
Kevin

OK, I think I see. So you're mostly interested in the security features the CC3220S offers, but won't necessarily utilize the WiFi?

Yes.

Will your MCU will be physically connected to the cellular modem? I'm a little confused how 1-3 come into this if so.

The MCU would be physically connected to the cellular modem on-board through a UART. I guess 1-3 are more related to the software stacks available for the MCU. For example, I wasn't sure exactly how it works on the CC3220, but it seemed like the ROM had some features to help with doing OTA firmware updates without bricking your device. Also, it seems that the sample projects for the CC3220 use SSL, but when I looked at using the NDK for the MSP432, there wasn't any support for SSL and it had to be implemented through expensive third party software.