Install OpenWRT on the Aruba AP-175

OpenWRT support for the AP-175 was officially available on March 26, 2023. The PR to Add OpenWRT support for Aruba AP-175 was created by Hurricos (Martin) on September 2022. Special thanks to Hurricos and all developers involved to make it happen.

Specifications

• Device: Aruba AP-175
• SoC: Atheros AR7161 680 MHz MIPS
• RAM: 128MB – 2x Mira P3S12D40ETP
• Flash: 16MB SPI NOR. Chip is vary from MXIC MX25L12845EMI-10G to Spansion S25FL128P
• WiFi: 2 x DNMA-H92 Atheros AR9220-AC1A 802.11abgn
• ETH: IC+ IP1001 Gigabit + PoE PHY
• LED: 2x int., plus 12 ext. on TCA6416 GPIO expander
• Console: CP210X linking USB-A Port to CPU console @ 115200
• RTC: DS1374C, with internal battery
• Temp: LM75 temperature sensor

Firmware

• Aruba AP-175 OpenWrt upgrade (sysupgrade)
• Custom u-Boot for AP-175, or build it from here

Installation Procedure Brief

Since stock u-Boot only allows signed kernel to boot (Aruba OS), A U-Boot replacement is required to install OpenWrt on this device.

• Use the CH314A SPI-Flasher or Raspberry Pi 4 and a 16-pin Test Clip (SOP16) to dump the SPI NOR chip
• Apply custom u-Boot for AP-175 on the SPI NOR dump
• Write the modified image to the SPI NOR chip again
• Boot up OpenWrt sysupgrade image via TFTP

Install u-Boot

Note that the stock bootloader on this device does not allow for unsigned kernels to boot, so replacing the bootloader is required for OpenWrt support on this device. The only way to do this is via directly writing to the SPI Flash. The custom U-Boot for the Aruba AP-175 can be found here. Besides, you can compile it from https://github.com/Hurricos/u-boot-ap105/tree/ap175.

To flash the SPI NOR you will need a 16-pin Test Clip (SOP16). You can use CH314A SPI-Flasher or directly wire the Raspberry Pi SBC to the SPI NOR with the test clip.

In this guide, I am using a Raspberry Pi 4 Model B, a “DIY 16-pin test clip” and flashrom application (on Raspberry Pi OS) to dump the SPI NOR.

Here is the main steps:

1. Create a full dump of the SPI Flash, and store it in a safe place
2. Erase and Clear 0x0-0x3ffff on the SPI Flash
3. Flash U-Boot to 0x0
4. Proceed to the OpenWrt Install Procedure

Detail guide for using Raspberry Pi SBC with flashrom:

• Make sure that SPI interface is enabled on Raspberry Pi OS. You can do this in raspi-config
• Make sure the AP-175 is power-off (disconnect PoE Adapter) before proceed

1. Create a full dump of the SPI Flash, and store it in a safe place

WIP