pbio/platform/prime_hub: Enable slots.

[laurensvalk]

Support for basic multi-program slots has been added a while ago, but it is not enabled by default while we wait on related featured to be completed.

This enables it for those who wish to try it out early.

Try it out

• Download the Prime Hub firmware file using the link in the post below.
• Install that file using these instructions.
• Code as usual using https://beta.pybricks.com/
• On the hub, choose slot 1 to 5 using the left/right buttons.
• A new program is downloaded to the selected slot.

Caveats

• There is no file manager yet. To delete programs, just download an empty program to that slot.
• Upgrading to a new firmware will erase the programs from the hub.
• All programs are kept in memory at once. If you write 5 giant programs, it will have a bit less memory remaining to run them.

[github-actions]

Download the artifacts for this pull request:

• pr_number.zip
• mpy-cross.zip
• nxt-firmware-build-3824-git4767e5f0.zip
• movehub-firmware-build-3824-git4767e5f0.zip
• ev3-firmware-build-3824-git4767e5f0.zip
• cityhub-firmware-build-3824-git4767e5f0.zip
• technichub-firmware-build-3824-git4767e5f0.zip
• primehub-firmware-build-3824-git4767e5f0.zip
• essentialhub-firmware-build-3824-git4767e5f0.zip

[coveralls]

coverage: 57.124%. remained the same
when pulling 225ff14 on slot
into dfbcfa8 on master.

[laurensvalk]

This no longer works.

Since updating Pybricks Code, it looks like we are now always sending 0 for the slot payload, so using the "current slot" never hits.

        case PBIO_PYBRICKS_COMMAND_START_USER_PROGRAM: {
            if (size > 2) {
                return PBIO_PYBRICKS_ERROR_VALUE_NOT_ALLOWED;
            }
            // Use payload as program ID, otherwise use active user slot.
            return pbio_pybricks_error_from_pbio_error(
                pbsys_main_program_request_start((size == 2 ? data[1] : pbsys_hmi_get_selected_program_slot()), PBSYS_MAIN_PROGRAM_START_REQUEST_TYPE_REMOTE));

I suppose it is not critical since we are not shipping this with the current firmware.

[laurensvalk]

This no longer works. Since updating Pybricks Code, it looks like we are now always sending 0 for the slot payload, so using the "current slot" never hits.

This can be solved with pybricks/pybricks-code#2343

[laurensvalk]

Closing since we enabled #312.