ADC conversion time of arduino uno and baud rate of arduino and RPI

Please answer for few doubts:

  1. what is the role of the baud rate while transferring data from Arduino to the raspberry pi?
  2. how much max baud rate of Arduino and raspberry pi?
  3. ADC conversion time of Arduino UNO?

Baud rate is the speed of transfer of serial data, the higher the baud rate the faster the transfer of data but at the risk of the increased need of accurate timing between MCUs to cause data corruption.

You should be safe with something like 250000 baud but I have seen people get higher speeds.
Be aware if your using the Arduino UNO(or other 5v MCUs) connected to the RPi then you will need level shifting to convert to 3.3V of the RPi and this may introduce external limits to your maximum baud rate.

ADC conversion speed of UNO can vary at the possible loss of accuracy. See the thread here as it highlights speeds and accuracy values.

No. The speed accuracy is the same in percentage terms for any baud rate. It might seem counter intuitive but it is true, it was a favourite exam question I used to set my students.

Basically the A/D conversion rate is about 10K samples per second. You can boost this to about 56 K SPS without loss of accuracy by changing the number in the prescaller register.

The Raspberry Pi is a bit more limited in the number of baud rates it can manage. There are some it can’t do, so basically pick one and set your Arduino to match it. Remember when receiving the data on the Raspberry Pi it is received as a byte array.

Just for information - STM32 microcontrollers have a much faster ADC and even higher resolution. As well as LGT8F328P by the way.

Yes but also the STM32 is NOT an Arduino.

And LGT8F328P is not Arduino but both can be programmed via Arduino IDE.

But the OP said

So is this an Arduino forum, or a forum for things that can be programmed by the IDE?
This forum is payed for by the Arduino company and its joint founder has said that it is for Arduino and its products.

Yes, OP asks about Arduino but if he needs a faster ADC I just recommend alternatives. OP also asks about the Raspberry Pi, which is also not an Arduino. In this forum I came across questions that have nothing to do with Arduino. I do not get paid for my attempts to help in this forum. If I have broke any rules, tell me and I will not participate.

Thank you, everyone. I have few more doubts. What will be a suitable baud rate for communication between Arduino Uno and RPI? and if I will increase the number of instruction codes in RPI or Arduino Uno does it affect the speed of data transfer?

The minimum required baud rate depends on how much data your sending and how often but starting with 115200 is a safe bet. If this is not fast enough then give examples of what your sending and how often and people here will try and help.