stdin and stdout

[techcatgato]

How do I use stdin and stdout so the robot sends the robot a list\str\int\tuple to a non code.pybricks IDE pc and how do I code the pc to receive it? Thanks in advance

[dlech]

When using the communication described in https://pybricks.com/projects/tutorials/wireless/hub-to-device/pc-communication/, everything sent over the air has to get converted to bytes. There are a number of ways this can be done. repr and eval, struct.pack and struct.unpack (module is ustruct instead of struct in Pybricks MicroPython), probably some others I'm not recalling at the moment

[dlech]

This is working for me (on SPIKE Prime):

import ustruct

packedx = ustruct.pack("<i", 654)
unpacked, = ustruct.unpack("<i", packedx)
print(packedx, unpacked)

Prints:

b'\x8e\x02\x00\x00' 654

A couple of tips:

• I added < to specify endianness. Most computers are little endian, so probably doesn't make much difference. But since data is going between computers, it's always nice to have an explicit endianness.
• unpack() returns a tuple, so the extra , after unpacked unpacks the tuple.

[DylDevs]

On the hub:

stdout.buffer.write(b"rdy") sends data from hub to PC

cmd = stdin.buffer.read(3) reads data from PC to hub

On the PC:

await send(b"fwd") sends data from PC to hub

def handle_rx(_, data: bytearray): receives data from hub to the PC

Is there a way to have a dynamic amount of bytes in cmd = stdin.buffer.read(3?

[laurensvalk]

You can check that data is available before reading it, so that it doesn't wait indefinitely when there isn't anything yet: https://pybricks.com/projects/tutorials/wireless/hub-to-device/pc-communication/

[techcatgato]

You can check that data is available before reading it, so that it doesn't wait indefinitely when there isn't anything yet: https://pybricks.com/projects/tutorials/wireless/hub-to-device/pc-communication/

Not sure if this is what you said or not, But I think he means a way to just send a message without the buffer element, and make the pc read the whole newest message

[DylDevs]

Yes.