A protocol is an agreement as to how two computers will communicate - using bytes or using strings is a small part of the protocol. No, the Arduino can not tell whether the data is a string or a byte. No linefeed is sent, unless you explicitly send one. If you send it as a string, 8 bits of data are sent to send the '1', then another 8 bits to send the '2', and, finally, 8 more bits to send the '9'. If you send a value like 129 as a byte, 8 bits of data are sent.
#Sending string over pyserial serial#
What is the difference between sending a string and a byte over serial? Are they both sent in the same format with the string just being several bytes followed by a linefeed ('\n')? Also, would the arduino be able to tell whether it was being sent a string or just a series of bytes over serial by Processing?.Lastly, if the data for servo A or B was an integer, would I need to convert it to a byte using byte(data for servo A or B) before sending it to the arduino over serial?.The first thing I thought of doing was having Processing write 'A', then servo A value, then servo B value.īut since PaulS said that it is not reasonable to expect to collect an entire packet in one loop, would it be better to have Processing write 'A', then servo A value, then 'B', then servo B value and use the following code? What is the difference between sending a string and a byte over serial? Are they both sent in the same format with the string just being several bytes followed by a linefeed ('\n')? Also, would the arduino be able to tell whether it was being sent a string or just a series of bytes over serial by Processing? However, there are still a few things I am unsure about. Thank you so much for your helpful replies! What you two said makes sense to me. If not, a different approach is needed (which servo is the data for?). So, you must prepare to deal with content loss.ĭo you need to send data for both servos every time you send data for one servo? If so, one approach will work (servo 1 data followed by servo 2 data, with, possibly, a delimiter in between). It does not guarantee that it will deliver each and every byte.
The system guarantees that it will try to deliver each and every byte. Therefore, start and end of packet markers make it a lot easier to know where in the byte stream a packet starts and ends.Īlso, serial data delivery follows the same guarantee model that the US postal service uses. Expecting, in one pass through loop, to collect an entire packet is not a reasonable assumption to make. If the data being sent can not fit in a byte, then conversion to string and back is generally easier to understand than sending the value as multiple bytes and reassembling them on the Arduino. Sending one value this way requires 1 byte. You would also not have to collect the characters into an array on the Arduino, keeping it NULL terminated, and convert the string back to an int. so you could send two bytes, and not have to do int to string conversion in Processing. To expand on what MikMo said, there are two ways to send data through the serial port - as strings and as bytes.įor a servo, where the position is an angle in the range 0 to 179, the values fit in a byte.
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