Electronics > Beginners
Need Help with STM32F407 Design
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Lt_Flash:
Also, why is there a 14.31818MHz oscillator? With some resistor between pins? Why 20pF? Was it calculated somehow? What type of crystal is that? Usually you calculate these capacitors based on datasheet, something like this (copied from SAML21 datasheet):

Crystal Oscillator Characteristics
The following Table describes the characteristics for the oscillator when a crystal is connected between
XIN and XOUT.

The user must choose a crystal oscillator where the crystal load capacitance CL is within the range given
in the Table. The exact value of CL can be found in the crystal datasheet. The capacitance of the external
capacitors (CLEXT) can then be computed as follows:
CLEXT = 2(CL - CSTRAY - SHUNT) ,
where CSTRAY is the capacitance of the pins and the PCB, and CSHUNT is the shunt capacity of the crystal.
Lt_Flash:
I would really recommend to copy-and-paste most of the parts of this evaluation board schematic for this MCU if you're just a beginner and not really sure what you're doing, would save you a lot of time and effort! :)

http://www.st.com/content/ccc/resource/technical/document/user_manual/25/21/69/1d/13/c5/4e/c9/DM00036746.pdf/files/DM00036746.pdf/jcr:content/translations/en.DM00036746.pdf
Lt_Flash:
Pay attention to all the bypass capacitors at VDD_MCU pins, they're there for reason!
jasons520:
Hi everyone, Thanks so much for your replies!
Some follow ups;
The 14.31818MHz oscillator is for the TVP5150 video decoder - the schematic for it is based on its data sheet.
I will update to use SWD, I'm quite confused when reading the datasheets, and ST-link for programming.
I will copy the discovery boards schematic to work everything else out.

The video decoder chip is using STM's dcmi on the chip. - its controlled via the I2C interface.
Im using SPI for wireless control via a NRF24l01+ module.

My main question is, do i just need the ST-link and SWD for programming the board, or do i need a usb port or something like that?

Thanks everyone!
andyturk:

--- Quote from: jasons520 on April 30, 2018, 08:13:34 am ---My main question is, do i just need the ST-link and SWD for programming the board, or do i need a usb port or something like that?

--- End quote ---
SWD/ST-Link is used for putting code on the board and also for debugging. There are various bootloaders in ROM that can also be used to reprogram the device from a serial connection like USB, UART, etc. However, those won't help at all with debugging. If you want to try the serial bootloaders, read up on AN-2606 and make sure you can reconfigure BOOT0 and BOOT1 as necessary.

I use a TC-2030 footprint on all my ARM mcu boards with the standard SWD pinout. It doesn't take much space and once you buy the cable, there's no need for putting a special connector on each project--it's just a PCB footprint.
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