D-Link DIR-655 Wireless Router

Table of Contents

1 Introduction

The D-Link DIR-655 is a 802.11 bgn and gigabit Ethernet wireless router. Its basic hardware is described on wikidevi with multiple hardware revisions.

2 Hardware

The main PCB with the main shield and heatpads removed reveals the main chip and the Ethernet bridge:


2.1 Main parts

Main parts are documented on wikidevi.

2.2 Connectors

Designator Footprint Description Notes
J1 2x5 pin 2.54mm dupont Debug connector? Unpopulated, 4 MHz clocked synchronous signal output
J2 10P 1mm FPC JTAG? Unpopulated

2.2.1 J1 connector

Pin number Description Notes
1 DATA  
2 Unknown Pullup to 3.3V, occasional glitches
3 GND  
4 Unknown 0V, likely N/C
5 Unknown 0V, likely N/C
6 CLK 4 MHz clock
7 Unknown 0V, likely N/C
8 Unknown Pull-up to 3.3V when powerup
9 +3.3V output  
10 Unknown Pull-up to 3.3V when powerup

A signal trace from the J1 connector has been obtained using a Saleae Logic analyzer. The dump can be downloaded here. Attempts at decoding the signal were made using the SPI decoder have not revealed any ASCII communications - the protocol working here looks to be binary in nature.

2.2.2 J2 connector

The trace from this connector has not yet been obtained.

2.3 The IP7150U CPU

The UBICOM IP7150U CPU is a non-standard (that is not MIPS, ARM or any other common ISA) architecture CPU with hardware threads designed for telecommunications equipment made by the now defunct Ubicom company now being a part of Qualcomm. There is no official alternative Linux builds for this CPU, there has been a GPL blob released by dlink http://pmdap.dlink.com.tw/PMD/GetAgileFile?itemNumber=GPL1100001&fileName=DIR655B1_FW200NAb33_GPL.rar&fileSize=8.1487082E8; There have been some attempts to build the firmware by James Hillard (https://github.com/jameshilliard/openwrtubicomstaging). Another source of information about this CPU is the now-defunct Ubicom wiki archived on the Wayback machine: https://web.archive.org/web/http://developer.ubicom.com/wiki/index.php. Unfortunately it looks like a "Ubicom Programming Dongle" is recommended for programming and debugging the SoC. The dongle is descrived as functionally equivalent to a JTAG header therefore it's possible that equivalent operations can be performed by any other JTAG dongle. It's not known where the official dongle can be purchased.

3 References

A brochure about IP7100 CPUs dlink-dir-655/DSASW0044772.pdf

Some links to the toolchain a ubicom32 kernel build from openwrt https://reverseengineering.stackexchange.com/questions/2720/what-is-the-ubicom32-toolchain-and-where-can-i-find-it

A datasheet (mirrored) for the Ubicom IP51xx processors which might have the same ISA as the IP71xx http://www.texim-europe.com/getfile.aspx?id=68544

Information about the Western Digital N900 which is based on a similar SoC (Ubicom I8K) https://openwrt.org/toh/western_digital/n900

GPL downloads for the Western Digital N900 https://support-en.wd.com/app/products/product-detailweb/p/179

Author: Maciej Grela

Created: 2023-01-11 16:43