Pico with HC-05 - how do you get it to work?

Hi,

I've not used the HC-05, but what you're doing sounds reasonable, I can't see an immediately glaring fault.

What value resistors are you using on that TX line from the HC-05?

It might be good to put a time.sleep(0.1) or similar after the serial = UART.. command, just in case a delay is needed for the serial to set itself up.

Also, you could try to use the .readinto method instead of .readline, in case there's a difference.

To debug further you might need to attach the UART to another USB-UART device instead of the HC-05, so that you can inject characters perhaps. It's a bit annoying having to do all this but I can't think of much more, unless you can find existing code for HC-05 with MicroPython.

It is a trimpot shabaz. I just adjusted it until I got about 3.2V out from 5V.

What is with this 3 x UART0 anyway?

It is 3 independent sets of UART pins or is it a single UART with multiple pairs of pins you can use with it?

Hi,

UART0 is a single UART, and you can use any of those three sets of pins designated UART0. Similarly, there is a second UART called UART1 and that can be internally configured to use any of the designated pins for that.

And is UART0 also connected to the USB socket?
In a similar way to 'Serial' (as opposed to Serial1, Serial2, Serial3 on Mega) on Arduino is.
On Arduino you just can't use Serial for debugging and communicating with a serial device at the same time.

If this is the same with UART0 on Pico then perhaps that is why I can't get it to work with HC-05?

Hi,

No, UART0 isn't tied to serial debug , it's normal to use it in your MicroPython code configured to pins as you have done. It certainly can be used for serial debug but you've configured it correctly from what I can tell.  

A voltage divider doesn't work well to level-shift digital signals.  Because it creates a filter with input capacity, it slants the signal edges.

Are you sure the HC05 is 9600 baud? I've had some that defaulted to other baud rates.

The HC05 runs off 3.3V. It often has a carrier card that has a regulator to interface to 5V MCUs, but you can bypass/remove all of that if you want.

Well they work good enough in most cases, with Arduino at least.

This worked finally:

serial = UART(0, baudrate = 9600, tx = Pin(16), rx = Pin(17), timeout = 10000)
strCommand = serial.readline()
print(strCommand)

The addition of 'timeout = 10000' made the difference.

But that was an educated guess.

No help from the Python doco.

It is about as useful as *** on a bull, unless you already know how to use the classes.

The same as Microsoft's documentation for their Microsoft Foundation Classes.