Hi, I am trying to design a RS232/RS422-to-UART converter with type-c USB. This converter firstly gets the info from a Fischer 10-pin cable input. The inputs are Timepulse, RX± and TX± of RS422, RX and TX of RS232, GND and Power-in pin. This module will work with the VBUS supply of the USB port and there will be a total of 6 indicator LEDs and 1 power switch which I connected to the voltage regulator’s voltage input. Since USB VBUS has 5V voltage and our data converter chips (MAX3232 and MAX3490) use 3.3V Vcc, I put a constant output (3.3V) voltage regulator. When the switch is open, there will be no voltage supply to the chips so the module will be off. There may be some uncomplete parts. I need the help of an experienced KiCad user to teach me little details I may have neglected or maybe a simpler or more correct way to design this kind of module.
Edit1-Some changes made: regulator changed, power indicator led connected differently; now, the cy7c65215 chip is being supplied by the voltage after the switch so that that chip isn’t supplied when the switch is open, either.
If you switch off with SW1 it is possible that U2 and U3 are still powered through the data lines since U1 is still powered on. Besides that your indicator LEDs will possibly not work the way you intended, since the data pulses are (most likely) in the kHz range, the LEDs will dim/turn on only slightly when there is traffic on the line (especially with such little current flowing through them).
how can I implement indicator LEDs for the transmitted/received data then ?
There are many different ways to implement this on the web. You could also do this in software by connecting the LEDs to the GPIOs of your interface IC.
Do your U1 GPIO correctly accept 3v3 input when it is powered from 5V. CMOS inputs if they are not TTL compatible can consume unexpected extra current when input voltage is not close to one of rails (0 or 5V in this case)?
Do your converter chips have 5V tolerant inputs? If not then protecting diodes at inputs (from input to supply) can make that chips being powered from U1 signal lines. Signal lines typically can draw something like 20mA what can be enough to power converter chips. Subtracting from 5V diode voltage drop of about 0.7V you can get 4.3V on converter chip supply.
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