Patrick Pollet

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9 years, 2 months ago.

DISCO-F746NG compiler issue

Hello,

this two topics shows the same problem with the DISCO-F746NG

https://developer.mbed.org/questions/60992/Downloading-or-running-compiled-code-fai/

https://developer.mbed.org/questions/61017/DISCO-F746NG_LCD_demo-have-you-got-it-wo/

Code from the online IDE can be downloaded only one time, others attempts bricked the board.

(using ST-Link for downloading the original HEX of the demo code could restore the board state).

Does the "MBED's Staff" knows this problem ?

Best regards

Patrick

Question relating to:

Last updated: 20 Apr 2021
The STM32F746G-DISCO discovery board (32F746GDISCOVERY) is a complete demonstration and development platform for STMicroelectronics ARM® Cortex®-M7 core-based STM32F746NGH6 microcontroller.

1 Answer

David Garrsion
9 years, 2 months ago.

Hi:

I got mine running by changing to an external 5V power supply instead of the default power supplies by the St-LINK USB connection.

I copied this from my comment to : https://developer.mbed.org/questions/61017/DISCO-F746NG_LCD_demo-have-you-got-it-work

"Interesting finding!!!!

See note at bottom of page 23 of UM1906. link for this .pdf is @ http://www.st.com/web/en/catalog/tools/PF261909

I was wondering what the power draw was of this board. I could not find it stated anywhere and it turns out it must be a lot as it can not be powered by a 500mA USB alone!

I did move the power supply jumper to ext 5v, connected a 5v 2 amp PS and loaded the demo again and ....IT WORKS!!!!!!!!! every time .......

go have fun as the demo graphics says....

I wish they (ST) had a note somewhere indicating this more clearly!!!

P.S. What is not clear to me is why the demo graphics shipped with the board works when the board is powered just by the USB St-Link ???????

D.G.

posted by David Garrsion about 7 hours ago Edit I just measured the 5V current draw from the ext. PS and it is only 420mA. ??

This is really odd as I have a USB power meter and it indicated a draw of 300, or so, mA when the board was "trying" to run the LCD demo....

I have made numerous mods to the LCD demo code and loaded it and the board runs it very time at the end of the upload. I also inserted printf statements and they work also! " D.G.

Maybe your USB cable is the problem. Some low-cost cables have rather marginal gauge power wires and that could result in a short voltage drop during flashing or while booting the LCD code. That may then lead to a crash of the code. The typical USB powermeter may not even detect these short powerdrops as they update the display at relatively slow rates. Try using a high quality ''fat'' USB cable.

posted by Wim Huiskamp 02 Oct 2015

Hi, running the demo on the board powered from the USB port here, it draws 0.46A at 5.03V (2.313W), so powering from an USB port should be fine. I can download the demo this way (again and again).

posted by Jack Berkhout 02 Oct 2015

Well... I scrounged thru my cable box and found a USB mini cable that "looked" heavy duty and Voilà!, the board runs the demo fine as advertised (my USB power meter says 0.42A @5.00V) . Who would have guessed a bloody USB cable problem,not me.......!

Thanks folks !!!

David G.

There still is the mystery of why the same cable would power the board with the factory installed graphics demo and also the power warning note at the bottom of page 23 of UM1906. link for this .pdf is @ http://www.st.com/web/en/catalog/tools/PF261909

posted by David Garrsion 03 Oct 2015