hub to hub communication failing

[leeehthy]

Helo, Pybricks community!
I'm a selflearner programmer that really need your help. I'm using two Spike Prime hubs. One of them has motion motors (hub 1) and the other has a claw (hub 2).
I'm smoothly handling the communication between the hubs, but when I send a message to one of them, it seems to get stuck in a loop.
It seems difficult to explain, but bear with me.
For example, hub 1 sends a message to hub 2 to lower the claw and everything works fine. But if hub 1 sends a message to raise the claw immediately afterward, hub 2 simply ignores the information.
I've already reviewed my code but I can't find anything wrong. Do you guys know something to do that can help me?

[BertLindeman]

Without seeing your code it is hard to state what might be wrong 😄

One hint might be: do you send the broadcasts faster than once per 100 msec?
Often it is good to have a wait(100) in the loop.

[leeehthy]

ohh, thank you for your answer.

isnt faster than that, I'm also using waits in my code.
its a big code, but ill send here the most important parts that are involved in the problem!

HUB ONE - with motion motors

HUB TWO - with claw

[BertLindeman]

You did not state the firmware you are running, and I know there has been a lot of work on bluetooth,
so I used the current beta firmware (geta.pybricks.com).

[EDIT] Made two simple programs, see a next post. They were one program shown twice.

Showing the programs as python text as that is easier to re-use elsewhere compared to images.

The motor in my test runs without any load, so your results may be different.

I added the timer to show that the observer receives multiple messages per second. That is normal Bluetooth behavior.

Your programs currently communicate using commands. In most cases it is better to communicate using status messages.

So instead of:

• "do claw up"

use:

• "set claw up"

At first that looks almost the same, but it changes how the receiving program handles the message.

Command:

• Receive "UP" → move the claw motor up.

Status:

• Receive "UP" → check the current claw position. If it is already up, do nothing. Otherwise move the claw up.

When messages represent status, it does not matter if one message is missed or if the same message is received multiple times. The receiver will still end up in the correct state.

[Sirus-7]

@BertLindeman. Hello Bert, you have set the same program (hub1 - hub2) twice.
😉

[BertLindeman]

u-oh, sorry, Thanks Friedrich.

Retry:

issue_2742_hub1:

from pybricks.hubs import PrimeHub
from pybricks.messaging import BLERadio
from pybricks.parameters import Color, Port
from pybricks.pupdevices import Motor
from pybricks.tools import wait

hub = PrimeHub()
radio = BLERadio(broadcast_channel=8)

while True:
    radio.broadcast("claw_up")
    wait(1000)
    radio.broadcast("claw_down")
    wait(1000)

issue_2742_hub2:

from pybricks.hubs import PrimeHub
from pybricks.messaging import BLERadio
from pybricks.parameters import Color, Port
from pybricks.pupdevices import Motor
from pybricks.tools import wait, StopWatch

hub = PrimeHub()
radio = BLERadio(observe_channels=[8])
claw = Motor(Port.D)
watch = StopWatch()

def claw_down():
    hub.light.on(Color.VIOLET)
    claw.run_angle(200, 100)
    hub.light.on(Color.MAGENTA)


def claw_up():
    hub.light.on(Color.YELLOW)
    claw.run_angle(400, -100)
    hub.light.on(Color.ORANGE)


while True:
    watch.reset()
    if radio.observe(8) == "claw_up":
        claw_up()
        print(f"after claw_up   {watch.time():>7}ms")
    elif radio.observe(8) == "claw_down":
        claw_down()
        print(f"after claw_down {watch.time():>7}ms")