DFR0781 (BT-401) Grace time for command execution unspecified.
Per.Svensson 2025-04-26 01:09:30 473 Views4 Replies Hello
In the wiki examples for sending commands to BT401 it becomes clear that some response is real slow.
Can someone specify the rules for sending?1. Is there a grace time after POR to obey? How long?
2. Is there a known max processing time for each command to obey?
3. What happens if a command comes to zoon? Ignored or messing up the previous?4. Is there a way to see when a command has been safely executed? Yes there are response messages, but they have no time stamping.5. Is there a logical relation between command and response?
That is - can a later response come from an earlier command and vice versa?
I really need some timing information.
Can anybody help here?
/Per
Usually, Bluetooth modules like BT401 (assuming you mean something like a Boltwood Technologies 401, or maybe a Sena BT401) require a settling time after POR.
Typical wait time is 500 ms to 1 second before sending any commands after power-up.
Some modules specifically mention 1.5–2 seconds to allow firmware and stack initialization.
If you send too early, commands may be ignored or cause a crash/reset.
ahsrab.rifat A few secends delay at boot time is ok, but after that command processing must be responsive.
The BT401 is also special in the sense that there is no “AT-command mode” . So in some magic way it distinguish between a command and just transparent traffic passing through. (Bluetooth traffic use the same UART as command messaging does)
How does this work???
I wish the BT401 designer had introduced a BUSY signal to one of the unused IO-pins !!!
That would have solved all my problems_
BUSY = 1: Command is processing and no commands are accepted over the UART
BUSY = 0: Command fully processed and response sent out on UART. New commands can now be accepted.
How easy life would have been if no guessing or unnecessary delays wold be necessary…
There are spare pins on the module, so why not use them?
