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stm32f7 custom pcb

Question asked by piet t on Feb 27, 2018
Latest reply on Mar 3, 2018 by Oliver Sedlacek

Hey everyone,

 

This is going to be a lengthy post but any help will really be appreciated!!

 

I'd like to integrate the MCU that I've been using into my final system(i.e no dev board)

 

I've designed PCB's in the past, but this feels a little more up there, so I just want a few checks

 

I've read the documentation although this is what I've gathered:

Documents used:

Datasheet

Getting started with STM32F7 Series MCU hardware development

bootloader application note

 

This is an overview of me designing the necessary hardware to get a device up and running. I have a few questions that I laid down in each section. I've split it into the same sections that the "Getting started with STM32F7 Series MCU hardware development" application note covers.

 

 

Power supplies:

 

The device needs a supply of 1.8V to 3.6 V.

In my design I'll be using a fixed ultra low noise supply, running at 3.3V.

 

I'll connect this to all peripheral supplies of the device(sdmmc and usb, etc.), therefore I can ignore the startup and shutdown curves.

 

I've also followed the following overview of the power supplies for the stm32f722ze:

 

 

And I've added all the specified parallel capacitors and followed the footnotes shown.

 

Voltage regulator:

The device has an internal voltage regulator that needs to be activated on certain devices.Looking at my technical manual it refers to the pin for activation as BYPASS_REG pin

 

Running through my pinout(LQFP144) It doesn't have one and this can be ignored(internally managed)

 

Power supply supervisor:

 

I've set the power supply supervisor to be on and plan on using an external battery to run the RTC during low power modes.

 

Clocks

On startup the device uses the internal 16 MHz clock, after which a external clock (4 - 26 MHZ) can be selected. This will be scaled to 216 MHz using the PLL's within the device.I'll use an external crystal running at 25MHZ for the main clock

 

Further a LSE clock can also be externally used.This will allow for the RTC to have a very accurate clock/calendar and for other timing functions. For the LSE clock I plan on using a External crystal/ceramic resonator (LSE crystal) at 32.768 kHz.

 

Boot mode

 

For the bootmode, there are a few different sequences shown in the manuals and application note an2606.

 

There are two boot addresses. And from the Application note A2606 It seems there are 10 patterns that can be applied depending on the chip. For the stm32f7222ze pattern 8 is selected. I'm not sure how to apply this to the board though.

 

I've read the following section from the "Getting started with STM32F7 Series MCU hardware development" application note. It seems that setting pin boot0 to 0V loads from flash and setting pin boot0 loads from flash? I'm not too sure about this though.

 

 

 

Debug management

 

To debug the board I plan on implementing the ST link that the nucloes come with.

 

It seems that I only need to decouple the jumpers(shown in red) and then use the swd pins shown in green to debug the board. I'll couple the pins shown in green to my custom board.

 

 

Looking at the nucleo-f722ze schematic for the header pins (shown above), I'm assuming I only need the following pins:

 

pin 2 : T_JTCK (SWCLK)

pin3 : connect to ground

pin 4 : T_JTMS  (SWDIO)

 

 

Thanks in advance for any help, I really appreciate it

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