Hi, I am using a STM32L496. On the board is a buzzer. If the buzzer works, an USB connection lost the transmit functionality. Receive is still ok. The supply voltage is stable regards Josef

[waclawek.jan]

And if the buzzer is disconnected, but still handled in software?

If this removes the problem, the buzzer probably generates too much interference, or you are overloading the mcu pin. In other words, in this case it's a hardware problem.

JW

[josef2]

Good morning jan,

thank's for answer. If I use the code without active buzzer (speaker 6Ohm on an class d amplifier and amplifier (SSM2305RMZ-R2) not activated) there's no problem. I think, it's a hardware problem, but is it possible to see in software that there is a problem. If so I can reinitiate the hardware.

best regards

Josef

[Peter BENSCH]

Here are a few notes: Class D amps generate relatively high switching currents with a high switching frequency, so it is very important not to let these currents get into the region of the MCU. Even if the SSM2305 works filterless, that does not mean that the loudspeaker wires can be of any length and can be laid as desired - the 280kHz switching frequency still runs over it. In addition, your 3V3 for the SSM2305 incl. GND must be cleanly separated from the 3.3V supply of the STM32 (layout: separated GND area & VDD: LC filter).
 
Regards
/Peter