Run code on MS Inventor Hub without PC

[lobodpav]

Is it possible to upload a code to the Mindstorms Inventor Hub and activate it without a PC being connected via BLE?

I.e. something like the original FW allows - upload a program under a number and then execute them by pressing the middle button.

[laurensvalk]

This is under development, see pybricks/pybricks-micropython#75

[lobodpav]

Thank you! Is the code "stable enough" to try it out? Or shall I rather wait? 😊

[laurensvalk]

That part is stable enough, but there are some other things to keep in mind.

We recently removed the concept of dual-booting the hub and the online installer is not yet updated, so you'd need to use pybricksdev to try this. And since battery charging is not yet implemented, you'd have to switch back to recharge the battery, which isn't very convenient.

[lobodpav]

I see. Without battery charging that makes no sense to use now. Will wait then, thanks!

[lobodpav]

Wondering if I can help in any way with the charging issue? Since I work on the volume control on the main branch, I lost the dual-boot. This is very annoying since my Hub has been discharged and now, if I understand it right, I have to

1. Restore original Lego FW (found 1.2 on the web)
2. Charge the hub
3. Re-install the Pybricks FW

The dual-boot was quite convenient for the charging, but since it's gone, the charging issue deserves to get fixed as soon as possible.

Also, installing Pybricks for 1.4 Lego Inventor FW is not supported yet, so I can' even check battery percentage as the official Lego app gets blocked until I update to the latest 1.4 FW 😞 Is there a way to find out battery charge level per cent? There is a battery voltage API, but since I don't know min/max battery voltage, it is difficult to estimate it.

[dlech]

You can find the LEGO v1.4 firmware at https://github.com/gpdaniels/spike-prime and use pybricksdev dfu restore xxxxx.bin to flash it to the hub.

The voltage levels are in https://github.com/pybricks/pybricks-micropython/blob/master/lib/pbio/sys/battery.c.

[laurensvalk]

I think @dlech is currently working on it. It was paused due to an issue with vbus detection, but that seems to be resolved.

We'll certainly appreciate an extra pair of eyes to review it when it is ready, just to make sure everything is safe. Almost all safety aspects seem to be handled in hardware, but double checking shouldn't hurt.

[lobodpav]

I see. Thanks for clarifying. Will gladly help any time possible.

[lobodpav]

It would be for the voltage thresholds to be available in the PrimeHub as properties. Or maybe even provide a new PrimeHub().battery.percentage() API, what do you think?

[laurensvalk]

Hardcoded constants can be documented, but a percentage method is certainly nice. We have considered it several times, but haven't settled on a good definition beyond a simple voltage scale yet. Particularly for the other hubs where everyone uses different batteries.

[lobodpav]

The percentage API would make sense for the LI_ION batteries anyway. For hubs with AA batteries, the percentage can't be really calculated. That's why I was thinking of the percentage API for PrimeHub only (not sure if any other HUBS use LI_IONs).

Yeah, the voltage scale is where most end up anyway. But gives at least some estimate.