This personal project is my first attempt at designing the schematic of a custom microcontroller-based circuit board. I based this design around STM32's B-L4S5I-IOT01A discovery board. However, I still have a few doubts regarding the functionality of this design, especially when it comes to the power delivery and the SWD pins.

I wanted to ensure this board is capable of being powered by an external battery that is at least 5V, or the 5V from my PC's USB port. I also made sure a switch would decide which power source would supply the microcontroller. I wanted to include the possibility of an external battery to make this circuit portable and not entirely dependent on USB unless I wanted to debug it.

The issue I have with the power delivery is that I'm not sure if I included the proper circuitry to make it work once it is physically powered. I'm not sure if the micro-B USB pins are correctly connected. Compared to the discovery board's schematic, I had to simplify it, since I only want it to supply power and allow UART communication with the MCU through the CP2102 component for debug purposes.

I also wanted to make sure this board is programmable, so I exposed the relevant SWD pins from the MCU. I am planning on using the detachable ST-Link programmer from a NUCLEO board. After a bit of reading online, I'm still not sure whether I need to also connect the programmer's VDD pin to the circuit board. And I'm not sure if I should I also power both the programmer and the board simultaneously when flashing a program.

Before starting the PCB layout of this schematic, I thought it would be useful to have an extra pair of eyes look at it to point out any obvious mistakes that I may have missed. I would appreciate it.

 

I see two pages of the PCB circuit, with no "POWER" line showing on the processor page.
I do not see any PCB layout at all.

 

Hi
The TS states.
Before starting the PCB layout of this schematic, I thought it would be useful to have an extra pair of eyes look at it to point out any obvious mistakes that I may have missed. I would appreciate it.
Also'
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I see two pages of the PCB circuit, with no "POWER" line showing on the processor page.
I do not see any PCB layout at all.

What exactly do you mean by power line? Do you mean the power that would supply the VDD pins? As for the layout, there is none since I haven't started it yet.

 

Hi
The TS states.
Before starting the PCB layout of this schematic, I thought it would be useful to have an extra pair of eyes look at it to point out any obvious mistakes that I may have missed. I would appreciate it.
Also'
E
View attachment 352577

What are the TS states?

 

Hello,

The TS is the topic starter or thread starter.
It is you who is refered to.

Bertus

 

Also I see that power flags have been added, which are necessary in Kicad in order to identify power source .

 

I'm still not sure whether I need to also connect the programmer's VDD pin to the circuit board.

I am not very familiar with ST devices, but in general the JTAG/SWD Debug Probes have a voltage sense pin (pin 1 on the Arm Cortex 10-pin connector, for example). This is normally used to sense if the target device is powered and, depending on the Debug Probe design, provide power to its internal voltage translators to match the power supply of the target processor. This pin 1 is connected to your VDD_MCU through a current limiting resistor (47 or 100 ohms, for example).

 

I see two pages of the PCB circuit, with no "POWER" line showing on the processor page.
I do not see any PCB layout at all.

MCU page gets 3.3V from the other page.
It is derived from USB or battery, 5V regulator

 

I am not very familiar with ST devices, but in general the JTAG/SWD Debug Probes have a voltage sense pin (pin 1 on the Arm Cortex 10-pin connector, for example). This is normally used to sense if the target device is powered and, depending on the Debug Probe design, provide power to its internal voltage translators to match the power supply of the target processor. This pin 1 is connected to your VDD_MCU through a current limiting resistor (47 or 100 ohms, for example).

So, I would also have to expose a 3V3 pin, which I would then have to connect to the VDD pin on my programmer. From the threads I've read online, it does seem to support it.

 

Pin 6 of cp2102 must be connected to vdd, you connected it to gnd.