PFP9W/howto Permanent Floating Plan 9 Workshop

Mediatek MT7688 & MT7628

The MT7688 and MT7628 seem to differ only in the setup of the wifi antenna. All references to MT7688 refer to both.

Key Features

The Mediatek MT7688 is a Mips 24KEc 32 bit little-endian cpu that runs at 580MHz. They have been widely used in WiFi routers, but since the built in Ethernet switch is limited to 100Mb, they have been pushed more into IoT use. Another thing to note about the 24KEc is that it lack a floating point unit but adds a digital signal processor. Most marketing materials advertise the DSP as useful in audio processing for VoIP.

They feature;

The onboard Ethernet is wired directly to one of the 7 ports on the Ethernet switch, so some minimal configuraqtion of the switch is required to get an outside connection. The standard u-boot will do this. Depending on where the u-boot came from, some of the GPIO may also be setup at boot to LEDs for power and port indicators.

Mediatek did release a dev board called the LinkIt Smart 7688 and made a number of datasheet and manuals available. Similar dev boards are available from Hi-Link and the Onion Omega2, along with still being sold by Linksys and others in budget Wifi routers and range extenders.

Docs

MediaTek MT7688 Datasheet v1.4

9front

A kernel for the MT7688 comes with 9front.

It currently supports;

To boot the kernel, ether use tftp or USB/SDcard and load a plan9.ini file to address 0x80010000 and the kernel to 0x80020000, and 'go 0x80020000' to run the kernel. The Ethernet switch is set to run ports 1-4 as a basic Ethernet switch, and port 0 is usually disbaled out of u-boot to be configured later as a WAN port.

ToDo

There is an experimental switch driver available. Unlike other wifi, which often use mdio for switch configuration, the MT7688 use mmio, so registers mapped to RAM.

Work was started on a WiFi driver. It currently gets as far as loading the firmware.

SPI, to be able to read and write onboard flash, as well as the Omega2 Dash whichuses SPI to drive a display.

And it would be neat if someone could find something unique to do with the DSP.