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I am trying to integrate an off the shelf wifi module with STM32f2 mcu over UART interface. I need to test the board after laying out the board. Is there a way I can test this UART interface before loading a binary to STM flash that talks to the WIfi module.

Can I do this communication (UART) testing using JTAG?

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what WIFI module is that? a link to a datasheet would be helpful. –  miceuz Jan 16 '13 at 7:38
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As far as I understood - you want to test WIFI module without hooking it up to a microcontroller.

In theory you could talk to it via UART directly from your computer using some USB-to-UART dongle, but probably WIFI module is quite a complicated beast, so this would involve amount of work similar to writing a program on a microcontroller.

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Not sure that's the question, but wanted to comment that even though writing the software for a PC may have comparable complexity, it often has the advantage of being able to more easily obtain debug output. For that reason, I'll often try to write my embedded code so that it can also be built for a PC. Often I do most of my development testing on the PC build, but try to remember to run on the hardware (if available) or at least build for it every now and then to be sure I'm not running down a track that will not work within the confines of the embedded system. –  Chris Stratton Jan 16 '13 at 15:45
    
@ChrisStratton yes that's a valid point, I myself try to modularize my code and write unit tests for it on PC –  miceuz Jan 13 at 7:33
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Most of the STM32 series has a UART bootloader which can be activated by strapping of the boot mode pins. If you can load code via the UART, and have it communicate with a program on a development machine, that would be a strong indication that the UART works...

If the module it normally talks to is logic level, you'll need a logic level serial (or serial-USB) adapter to connect it to a PC.

In theory you could use JTAG boundary scan (if the documentation of the chip says it is supported) to set or read the state of the UART pins and compare them against an external stimulus or reading. But it's probably simpler to load a test program (possibly into RAM) via the JTAG or SWD (or the UART bootloader mentioned above) to exercise the UART.

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Thanks for the info. I feel UART bootloader is the way to go. Can you please more on how it works? –  Elsa Adams Jan 16 '13 at 4:01
    
ST has an app note somewhere, the specific device data sheets have the boot pin strapping, and there's software to use it at code.google.com/p/stm32flash –  Chris Stratton Jan 16 '13 at 15:42
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