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CC3100 external memory/flash requirements?


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#1 xc2rx

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Posted 13 July 2015 - 06:19 AM

In the CC3100 datasheet, http://www.ti.com/li...link/cc3100.pdf, it says that the chip requires an external flash memory IC for its file system storage such as service pack file, system files, configuration files, certificate files, web page files, and user files. In the Netduino 3 Wi-Fi schematic, I do not see any external flash IC connected to the CC3100 IC. How is this possible?

 

If I have to guess, the CC3100's file sytem is probably stored in one of the 2 flash banks of the STM32F427. If that is true, then there must be a software layer running on the STM32F427 emulating an external flash IC supporting the required commands. But that's just a guess, can't really tell unless the firmware source code is revealed.

 

You can read about the external memory requirements on pages 29 - 30 in the datasheet.

 

 

Another question, is the STM32F427 talking to the CC3100 through SPI or UART? In the datasheet, it mentions that SPI can achieve up to 20MHz data transfer speed when UART can only do 3Mbps baud rate max. Giving the fact that the CC3100 can achieve a TCP throughput of up to 13Mbps and UDP up to 16Mbps, it would only make sense to use SPI over UART. In the schematic, I see both SPI host and UART host connected from the CC3100 to the STM32F427. So not sure which interface is really being used unless the firmware source code is revealed.



#2 xc2rx

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Posted 13 July 2015 - 06:26 AM

Here's a link to a similar question asked on the TI forum: https://e2e.ti.com/s.../f/968/t/407760

 

The TI employee that answered the question stated "So unfortunately you need the serial flash as some system and configuration files are required for proper operations." Hmmm....



#3 xc2rx

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Posted 13 July 2015 - 10:11 PM

Nevermind, I found the answers to my questions by looking through the CC3100.cs file. I'm surprised a link to the Netduino github repository isn't mentioned anywhere on the website but only in some of the Forum posts. 

 

Anyway, I found out that the TCP/IP stack that comes with the CC3100 isn't being used and that's why the external flash IC isn't needed. Instead, Netduino uses its own TCP/IP stack, the Netduino.IP. In my opinion, having the STM32F4 handles all the TCP/IP processing is a waste of RAM and CPU processing power. The CC3100 was designed to do all of those heavy lifting stuff so that even a small 8-bit ATMega MCU can make use of it. But it's understandable that sacrificing a bit of resources reduces the BOM cost of the board (by not needing that external flash IC). Might be more cost effective to use a different Wi-Fi IC minus the built-in processing power for handling a TCP/IP stack (since that's being handled by the host MCU). Either way, it is a very interesting approach how the CC3100 is being used in this case.

 

Also, the Netduino 3 was wired so that either the SPI host or UART host can be used to communicate with the CC3100. 



#4 Chris Walker

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Posted 13 July 2015 - 10:21 PM

Hey xc2rx,

Two quick things:
1. Netduino 3 Wi-Fi uses a hybrid stack version of Netduino.IP. It's letting the CC3100 do all the low-level sockets and buffering logic and taking care of the upper-layer interfaces, network configuration, wireless integration, etc. [CC3100 also has raw sockets support...which is where you'd marry the full Netduino.IP stack to it.]
2. The CC3100 module on Netduino 3 Wi-Fi has a flash chip inside it. If you want, you can look up CC3100MOD on the TI website for all sorts of technical detail goodness.

Chris

#5 xc2rx

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Posted 14 July 2015 - 12:25 AM

OH!!! I didn't realize that CC3100 and CC3100MOD are different. Now that makes complete sense. I just ordered a Netduino 3 from Amazon. By the way, will it be possible for you to provide the part number for the JTAG header? Just in case I want to debug the firmware using my Segger J-Link. Thank you!



#6 xc2rx

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Posted 14 July 2015 - 12:43 AM

Nevermind, I found the JTAG connector part number in the schematic: FCI 20021121-00010C4LF



#7 Chris Walker

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Posted 14 July 2015 - 01:02 AM

Nevermind, I found the JTAG connector part number in the schematic: FCI 20021121-00010C4LF


Since you picked up your board from Amazon, here are some Mini-JTAG headers from Amazon to go with it. These are SMD and go on the bottom side (with notch on the same side as the golden arrow pointer).
http://www.amazon.co...6835668&sr=8-17

Chris

#8 xc2rx

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Posted 14 July 2015 - 02:11 AM

Damn I already bought some connectors from Mouser.






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