Linksys wrt1900ac

The Linksys wrt1900ac v1 is a router that was released around a decade ago.

It was supposed to be designed to run OpenWRT, and included features to accommodate this such as:

• Dual flash makes it harder to brick the device by flashing a bad firmware image, by giving you the option to boot to the previous firmware.
• Cooling fan with software PWM speed control

Unfortunately however, it came with a Marvell wifi adapter for which the driver source code was never released, and the Marvel provided no assistance for the creation of open source drivers for their adapter.

This meant Linux drivers for that adapter have always been a reverse engineering exercise, and wifi performance under OpenWRT was average at best.

To this day, Linux driver support for the Marvel wifi adapter in this router is average at best.

 

WiFi

The wrt1900ac v1 is the only variant which had it’s wifi adapter on a removable dual mini PCIe card, allowing it’s poorly supported Marvell wifi adapter to be removed to free up two mini PCIe slots.

All other variants of this device have the wifi adapter integrated into the system board and do not have mpcie slots – and for this reason I steer clear of them, even though some have more RAM and slightly higher specifications.

I populated one of these slots with a MediaTek DR7915, which gives it tri-band wifi AP capability with full OpenWRT driver support. MediaTek are a manufacturer that support open source driver development, and their AP grade wifi adapters are superb. Always ensure that Linux drivers are well developed before purchasing any hardware that is to be used with OpenWRT.

The standard quad wifi antenna array has been replaced with a tri-band antenna – I chose a stand alone unit rather than mounting the antennas to the unit. This allows the antennas to be placed in an elevated location away from the router it’sslef.

It’s worth noting that many wifi adapters for laptops have limitations when they are used in access point (AP) mode – they are meant to connect to an access point, and will only connect at 2.5ghz if configured to be the access point. Intel cards like the AX210 are like this. A good card for a wireless router will obviously be one that is designed primarily as an access point – such as the MediaTek DR7915 or similar.

My upgraded single mpcie wifi adapter provides flawless WiFi6E connectivity at up to 1200Mbps, and provides more than double the throughput of the original adapter whilst only using two antenna connections and using only one of the mpcie slots.

It would absolutely be possible to fit an additional wifi adapter of the same type if required.

TTY Serial Terminal Interface

Like many embedded devices, the wrt1900ac has a 4 pin onboard header, which can be interfaced to a PC via a USB or serial UART to provide a serial terminal interface – it’s pretty cool to actually watch the thing boot, knowing that you can still configure and flash the device even if you stuff up it’s network connectivity.