Hi Ian, Rhythm Droid here. I'll be happy to help you with that.
The best way to slave your BSP to Squid is to use MIDI Clock, because MIDI Clock contains both tempo data (sometimes referred as "sync or clock") and also start, stop, and reset (sometimes referred to as "transport") messages.
Squid can send either or both of these from its MIDI OUT ports to slave other gear. To slave the BSP to Squid, you'll want to send both.
Let's first get Squid to output the basic tempo data from the MIDI OUT1 port.
1) Enter Global settings by pressing [GLOBAL]
2) Rotate encoder until you reach item 11-B "MIDI OUT Settings - OUT1 Sync"
3) Push encoder once to move the cursor to the right hand screen
4) Rotate encoder until option "Send" is selected
5) Push encoder again to confirm
Next, we'll make sure Squid also sends the start/stop/reset transport messages that will instruct BSP to start playing at the same time Squid starts playing.
1) While still in Global settings, rotate encoder to item 11-C "MIDI OUT Settings - OUT1 Start/Stop"
2) Push encoder to jump to the right hand screen
3) Rotate encoder to select "Send"
4) Push encoder to confirm
5) Push [BACK] button to exit to home screen
Now, connect a MIDI cable from Squid's MIDI OUT 1 port to BSP's MIDI In port (you will have to use the dongle Arturia included with the device to convert from a standard 5-pin MIDI cable to BSP's 1/8" miniature MIDI port.
If BSP doesn't slave to Squid right as soon as you hit play on Squid, you may need to refer to the BeatStepPro manual to make sure that it is set to receive both MIDI Clock and Transport commands, and you should be good to go. Let us know if you got it working!