# Releases and versions

A firmware release is a number: 101, 104, 105, … Every release is a tag `V<number>` in the
[firmware repository](https://github.com/Source-Robotics/Spectral-Micro-BLDC-controller) and a GitHub release that
carries the image `spectral-bldc-firmware-V<number>.bin`, a manifest `firmware.json` with the image's size, SHA-256 and
the commit it was built from, and the release notes. The notes are the firmware's changelog; the
[appendix](https://docs.source-robotics.com/Spectral-BLDC-docs/107/appendix/firmware-release-notes/) collects them.

## Which release does my driver run?

```
#Info
```

prints `Software version: <number>` among the rest; Motor GUI shows the same number in the driver's identity, and
over CAN Send_Respond_Device_Info returns it as the third byte. From firmware 105 the number is the build's own
version. Before that it was read from the EEPROM, where the last `#Default` wrote it, so it names the firmware
that last restored the defaults, not necessarily the one running: 101 and 104 both write 101.

### Drivers that report 101

A driver that reports 101 runs either release 101 from the `main` branch, without a bootloader, or release 104
(or an earlier build of `Bootloader_main`), which also writes 101 and runs above the bootloader. Drivers sold before
release 105 shipped with firmware 101 or 103.

To tell whether yours has the bootloader, power it up while `bl_flash.py list` or Motor GUI's *Scan bootloaders*
is polling: a driver with the bootloader answers in its first two seconds. With the bootloader, update it to the
current release as in [Updating through the bootloader](https://docs.source-robotics.com/Spectral-BLDC-docs/107/07-firmware/update/); the release it ran before does not matter
then. Without one, install it first: [Installing the bootloader on an older board](https://docs.source-robotics.com/Spectral-BLDC-docs/107/07-firmware/bootloader/).

## Which release does this site describe?

The one in the version box on the [landing page](https://docs.source-robotics.com/Spectral-BLDC-docs/107/) and in the version selector in the header. When a
newer release changes what a page says, a new version of the site is published and the previous one stays
reachable from the selector. The [compatibility table](https://docs.source-robotics.com/Spectral-BLDC-docs/107/appendix/compatibility/) says which releases go with
which bootloader, Python library and PAR6 runtime.

## The STEPFOC counterpart

Most Spectral Micro releases have a [STEPFOC](https://docs.source-robotics.com/STEPFOC-docs/) release with the
same changes. The numbers do not always match: the current pair is Spectral Micro 107 and STEPFOC 108, and the
[compatibility table](https://docs.source-robotics.com/Spectral-BLDC-docs/107/appendix/compatibility/) lists the others.

## The two branches

Releases from 104 on are built from the `Bootloader_main` branch of the repository, whose firmware is linked to
run above the bootloader; 104 is the first of them. The `main` branch holds the firmware linked to run without a
bootloader: release 101 and earlier, and a few later changes that were never tagged as a release (among them
the Kt request and the voltage limit message). It is not updated.

Version `101` of this site documents a board running 101. It also fits 104, which adds the Send_Respond_Kt
request, Send_Voltage_Limit (in the release image) and the bootloader. The 104 release image was built from
commit `20765c9` on `Bootloader_main`, not from the source at the tag `V104`, which does not have
Send_Voltage_Limit yet. To move a board without a bootloader to a
current release, see [Installing the bootloader on an older board](https://docs.source-robotics.com/Spectral-BLDC-docs/107/07-firmware/bootloader/).