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Among all the discarded and old devices that I find or close people give me, I had an old Speedy ADSL router in my closet (Speedy was an old ISP). The device in question is an Huawei HG532s. This router comes with a USB port. Knowing that routers usually have an embedded Linux system on it, we can imagine several possible scenarios to use that USB port, different from the default one that they come with (they are mainly designed to connect a disk drive that could be a pen drive and access files from the network, or to connect a 3g modem). An interesting scenario is to be able to connect an audio interface and do something that “sounds”. I remember that some time ago I came across a similar project that created a kind of “WiFi Radio” when stuff like Chromecast did not yet exist on the market: The interesting thing about that project is that it used OpenWRT, which in other words means that a modified version of Linux already existed for that particular router model that could include native support for audio cards (installing a package in OpenWRT is quite handy with the opkg tool). I decided to create a delay effect, mainly because of the attractive idea of ​​programming my own dsp algorithm in C++, although it is simple algorithm, I have never done anything like this before.

Searching for device information
First of all, it was necessary to see how much information about the router was on internet and how we could access the system to modify it. I came across where [danitool] shared with the seguridadwireless community a bunch of steps to install the firmware of another similar TPLink router that brought many more functions, in a router like mine. The firmware change worked perfectly because the hardware was exactly the same. This was an excellent starting point, because to develop the project I modified the tplink firmware that [danitool] uploaded. The mtd tool was already integrated there, which made things much easier when flashing the system partitions. The same thread mentions the toolchain available in the GPL package of the ASUS DSL-N14U router (another router with identical hardware), necessary to compile the kernel, libraries and programs. In addition, on the official TPLink page you can find the GPL package of the router mentioned by [danitool], TD-W8968 v2 (download here). This package was used to compile and modify the linux kernel, making use of the toolchain available in the ASUS GPL.”

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