Test project: hello_world from SDK demo_apps
We have noticed voltage spikes on our project board with Kinetis MK22FN256VLH12, they occur when UART0 TX pin state changes.
I have reproduced the problem when FRDM-K22F demo board and the simple hello_world project.
VDD supply is monitored with a scope trigged by UART1 TX pin state changes. TX pin is PORTE0 for hello_world project.
The spikes can reach 600 mV peak-to-peak with default project settings.
They can be reduced down to 60 mV peak-to-peak when the slew rate is configured to Slow with full pin configuration using PORT_SetPinConfig as shown in attached file.
60 mVpp is still too high if running ADC simultaneously.
Question: are there other settings (hardware and/or software) to further reduce these spikes?