STM32L476VGT3 not booting on my pcb card

[linusjonsson]

Hi, my mcu is not showing up in st-link v2 :(

Currently boot0 i low, 10k resistor to gnd.

All voltages are stable on vdd and no short circuit is detected.

Any tips or possible solutions to my problem?

My schematic can be found here: https://gyazo.com/836f25b0cbac1570c4dc0bceeff82472

[Tesla DeLorean]

Nothing in the schematic immediately jumps out.

Pin 19 of the JTAG will have 3V from the ST-LINK on it.

What is the ST-LINK Utility or STM32 Cube Programmer reporting as a voltage on VTarget?

Check orientation of package on PCB

Check pin numbering

Check level on NRST

[linusjonsson]

Thanks for answer!

Pin 19 on jtag is nc? Should be 10k to gnd, or am I wrong here?

Nothing is showing up in ST-LINK Utility so cant see VTarget yet.

Orientation of package is ok.

What level should it be on NRST?

[linusjonsson]

Still haven't figured out whats wrong, anyone that might know?

[Tesla DeLorean]

Schematic is a bit illegible, could do with being twice the resolution so the names are readable.

You have PCB image?

NRST should be high

Pin 19 is generally uncommitted, however Segger used it to output 5V and ST 3.3V, as a means to power a board. I'd leave the resistors off Pin 17 and Pin 19

ST-LINK should be able to report voltage even when it can't speak to the core.

[linusjonsson]

[Piranha]

Currently boot0 i low, 10k resistor to gnd.

That is not true. R6 and R7 forms a voltage divider. Also I don't understand why do You pull R6 up to 5V, when it should normally be pulled up to VDD (3,3 V). In this case it divides voltage to 5 V / 2 = 2,5 V, which is bad, because BOOT0 pin's high level is at minimum 0,77 * 3,3 V (VDD) = 2,541 V. So it turns out to be undetermined and close to high level, but it definitely is't low level, which is at maximum 0,17 * 3,3 V (VDD) = 0,561 V. Measure the voltage on BOOT0 and at least for testing connect it to GND by switching ON switch at pin NO_1 and all other switches OFF.

Minor comment.. Reset button circuit seems to be overly complicated.

[linusjonsson]

Understand your point, but i have cut the trace (5V 10k) so boot0 is only connected to 10k resistor to gnd. So that should not be any problem!

[Piranha]

OK, so BOOT0 is OK for now. By the way, if You didn't find it - AN4555 is pretty nice. 🙂

Maybe soldering problems? On LQFP packages pins can be measured with multimeter. Check all the power supply, BOOT0, NRST voltages on MCU pins. And also VSS voltages by measuring these against 3,3 V supply line.

[linusjonsson]

Have done some measurements, results:

VDD1: 3.29V

VDD2: 3.29V

VDD3: 3.29V

VDD4: 3.29V

VDD5: 3.29V

BOOT0: 0V

NRST: 3.17V (1.45V with ST-Link v2 unpowered) (3.17V with power)

Still nothing showing up in ST-LINK..