This repository provides device tree overlays which can be loaded on top of the base device tree.

There are multiple variants of the SMARC-sAL28 in respect of the network and audio functionality. Board variant 1 has just one ethernet port without TSN functionality but has all four SerDes lanes available for the user. Board variant 2 has two ethernet ports and an audio interface. These ports are connected to the internal switch, thus it doesn't have any direct ethernet connection, but it makes the board perfect for ring topologies. Board variant 3 has one (TSN-capable) ethernet port. Board variant 4 has two ethernet ports (one TSN-capable and one standard one). Both variant 3 and 4 have a special QSGMII lane available, so that the four internal switch ports can be exposed on the carrier board.

Kontron officially supports two different carriers. One generic "SMARC evaluation carrier 2.0" (carrier-ads2.dtso) and a "KBox A-230-LS" tailored to the SMARC-sAL28 board (carrier-s1914.dtso). These overlays provide nodes for the devices provided by these carriers.

The board provides a display port which can also be used as a embedded display port. Loading embedded-display-port.dtso reconfigures the port as eDP.

Due to pin restrictions the CPLD shares GPIOs which are needed during CPLD update. By default, the device tree contains nodes for the CPLD. Loading no-cpld.dtso disables all CPLD devices in the device tree. Thus, the GPIOs are free again and can be used to update the CPLD.

The second CAN port can be enabled if both the carrier and the module support it. Load can1.dtso to enable it. Please note, that this also requires a modified RCW, because CAN1 shares pins with the I²C PM bus.

The I²C GP and PM bus can be switched to 400kHz by using either i2c-gp-400khz.dtso or i2c-pm-400khz.dtso.

By default, only one 2.5Gb/s link to the internal switch is active. This acts as a sepecial CPU port. A second port can be enabled by loading the overlay eno3-swp5.dtso. This port has no TSN capabilities and just has a speed of 1Gb/s.

The KBox is available in different flavours and configurations, too. The first serial port can be in RS-232 mode (carrier-s1914-ser0-rs232.dtso), in RS-485 mode (carrier-s1914-ser0-rs485.dtso) and RS-485 full duplex mode (carrier-s1914-ser0-rs485-fd.dtso). Also the second CAN port can be enabled if both the carrier and the module supports it (carrier-s1914-can1.dtso).