[Solved] Hello from Northumberland, UK

Welcome! I grew up down the road, outside middlesbrough. You're in a beautiful part of the country.

This sounds like an interesting project, and I love the fact you're teaching at the school! I'm sure people here can help you out.

Hi SwarlandRB

Welcome, lots of helpful members here, so ask away!

Ron B

@swarlandrb Welcome, to the forum.

@swarlandrb

Are you going to code you rpi pico in C++ or micropython?  Either will work fine and micropython would be a good compliment to the python you run on your Rpi.  Passing a parameter from one pico to another (or even pico to rpi can be done in multiple ways and much will depend on how close the boards are situated or if you are using an additional wifi board to use with the pico.   I often complement a rpi pico with the likes of an ESP8266 to wifi enable it (usually a cheapo Wemos ESP8266 mini).  

I hope your railway runs on time 😋 

@byron I have completed one railway project in micropython and would want to move onto the next railway project using micropython too.  The club uses a system called CBUS, designed by a group called MERG in the UK, it uses a bus system to transport event messages throughout the layout; however, it doesn't create routes from a start signal and a destination signal.  Our main station throat has a complex of crossings and routes that would be easier to control using start and destination buttons, but even by using a switch matrix, we wouldn't have sufficient GP outputs left 9n one Pico to create switched inputs to the CBUS system.  Therefore, I would like to have a second Pico a few inches away from the first Pico, connected probably using the serial facility, so that number 1 Pico can send a message to number 2 with a numerical code of 2 digits that would then trigger an output from Pico 2 into the CBUS input board and create the appropriate CBUS event and associated turnout switching to create the desired route.  I have already made test programs for most of the elements, but I need the easiest way for Pico 1 to talk to Pico 2.  I would probably want Pico 2 to acknowledge the Pico 1 message. 

Posted by: @swarlandrb

but I need the easiest way for Pico 1 to talk to Pico 2.  I would probably want Pico 2 to acknowledge the Pico 1 message. 

A simple serial UART comms twix the pico's would do the trick I think.  Its passed my bedtime right now so I will give it some more thought tomorrow.    

@byron many thanks, past mine too.

@swarlandrb

Not yet focused in on your requirements, but SWMBO has allowed me a tea break from preparing the earth so she can plant her first early potatoes. 😎 .  You indicate you wish to pass a 2 digit code, as I was wondering how many different codes you might be passing and what sort of thing triggers the second pico to send this code. Also how many of each pico's pins are free and what other things are attached to them?

And whilst I was sipping my tea I browsed for info about the MERG CBUS.  I see its a CAN bus system.  I wonder if the pico CAN bus as in the link below is of any relevance to your project.

https://www.cnx-software.com/2021/05/26/canpico-open-source-board-adds-can-bus-to-raspberry-pi-pico/

@byron 

I have looked at the Pico CAN bus add-on board, but I don't really know enough about the system to know if I can create an event straight onto the CBUS. 

My thoughts for the program are that the operator would select the route start and end by pressing a button switch in both locations followed by an activation button; the switches will be wired into a 5x4 switch matrix and detected in Pico 1, the start and end button values would be identified from the matrix and added to a buffer.  Once 'activated', the buffer contents will lookup a value in a python dictionary, the new value will equate to a GPIO pin number and this will be transmitted to Pico 2 to activate the appropriate output, which will be sent to a MERG CBUS switch add on board. This board creates the appropriate CBUS event to switch to the route required.

There will be 9 input lines from the switch matrix, plus a couple of others on Pico 1, 15 or so routes outbound on Pico  2, so not too many spare pins, but hopefully enough to activate a UART function on each Pico.  I don't know enough about serial-to-serial connections to be able to tell how it would actually have to work, but basically I want Pico 2 to listen out and Pico 1 to send the 2-digit number, Pico 2, after checking the received number is between 1 and 20 say, will acknowledge receipt back to Pico 1, who if acknowledgement hasn't been received within a specified period, would resend the message.

I have tested the matrix input and the python dictionary lookup and they both work well; the Pico 2 output program will be straightforward, just the bit in the middle I need now.

@swarlandrb

To quote from the micropython rpi pico docs 

There are two UARTs, UART0 and UART1. UART0 can be mapped to GPIO 0/1, 12/13 and 16/17, and UART1 to GPIO 4/5 and 8/9.

I think you will only need to use one of the UARTs on each board, and it wont matter which one, so are any of these pins available on each pico?  And I should say you only need one of the pins pairs for each board

@byron

Yes, I can arrange for a pair to be available on each board.

@swarlandrb

I should also ask how you are powering you pico's, is it from the usb connection or via the VSYS pin

@byron 

I had intended from the usb connection via a twin 3.1amp plug.