Gustfu wrote: ↑
Fri Feb 28, 2020 3:53 pm
Hello, I'm a beginner. I'm wondering about the order in which pi operates. I know I shouldn't connect sd card after boot.
My question is it ok to build/modify the circuit after the boot and also is it safe to plug in mouse, keyboard, monitor, ethernet after the boot?
Please explain why I should do it this way also. Maybe there's an order I need to learn about?
If the SD card is not inserted when the Pi is powered up, it won't boot. That SD card is the equivalent of a PC HDD.
You should not connect or disconnect anything to the GPIO header while the Pi has power. It's far too easy to make a mistake and either brush a pin or connect the wrong things together and destroy the Pis SoC. And this points up the need to double-check all GPIO connections before applying power to a Pi.
Part of the specification for USB is "hot swap". That is, you can plug or unplug USB devices to a powered up, running system. This also applies to Ethernet cables and HDMI cables. Mind you, connecting the HDMI cable(s) after boot may not get you a working display image as it is--at that point--too late for the VC6 to read the EDID data. However, if you set force HDMI and specify the correct display parameters (width, height, and frame rate at a minimum), doing so will work.
What you *should* do is connect everything else to the Pi before you connect power. That way, the Pi can boot with the intended peripherals and GPIO connections. Do this routinely and it will become a habit and your experiences with Pis will be much more pleasant than if you don't. Note that some or all of these connections do not apply if you are going to run the Pi "headless". Also, if you set your Pi up with ssh and/or VNC active, you can, with just a WiFi or Ethernet connection you can login in remotely and change anything that needs changing up to and including shutting down or rebooting a Pi.