2013-04-16 04:31 PM
Hi,
currently I am trying to analyze the STM32F4Discovery schematic to get a minimal circuit using a STM32F407 oder STM32F405 in LQFP100. So I started an now ended up completely confused with a whole bunch of questions in my head: 1. Could anyone have a look at my minimal circuit? >>>>>>>>>>>>>>>>>>>>>>>http://www.uploadarea.de/files/pekgj4xyk4c9yujy1m6oawxqz.pdf
<<<<<<<<<<<<<<<<<<<<<<<<<<2013-04-16 05:14 PM
I personally would do a single 10K for each on the BOOTx pins, with jumpers to VCC or GND. The arrangement ST has allows you to short with tweezers.
The MCO pin has often been used by DISCOVERY designs to provide 8 MHz to the primary CPU by using the 8 MHz from the ST-LINK CPU, which needs a crystal for USB. This would eliminate one 8 MHz crystal from the DISCOVERY BOM. A crystal based clock is desired for USB or CAN. NRST is bidirectional, assume you don't want the other processor driving it. Would perhaps add support for the LSE crystal on PC14/15, needed if you want to try STANDBY and RTC functionality. Honestly not hot about ST's evolving SWD header, would personally go for a classic 20-pin JTAG, or 10-pin SWD. Go with what even works for you, add options for multiple different header placements.2013-04-17 12:27 AM
So for my conclusion:
1. BOOTx pins: 10k (btw. can you explain to me why the really make use of a voltage divider? For each BOOTpin both resistors + SB are placed.) 2. MCO pin: forget it. not important for me 3. thanks for the RTC hint 4. In other words I need to remove the SB connecting the DiscoveryNRST-pin to the DiscoveryST-Link in order to use the ST-Link for external programming??? 5. Unfortunately I dont have enough space for a 20pin JTAG. I'd like to use the 6pin although I in general don't like connectors which are not protected for reverse polarity. 6. Did you have a look at my JTAG connection? I don't want to order some PCB and not get a connection to the STM32F4. Thanks for you help. Short and precise. Excellent. Thanks.