![]() ![]() ![]() 2x7 Header Electrical Characteristics Table Also using a multimeter, we will measure the impedances of the pins to GND and Vcc when the device is powered off and on, and also measure the voltages of the pins. The easiest pins to identify are GND, which can be verified by performing continuity tests using a multimeter. The next step is to start identifying some of the pins. The following figure highlights the traces in white. Removing the daughter PCB connected via J6, we see that there are a few traces that run to QCA9558-AT4A, making it a likely candidate for JTAG or another debug interface for this SoC. The 1x4 header is most likely UART serial, and it does not have enough pins to be considered for JTAG, so let us focus our attention on the 2x7 header. Looking closer at the board we see two headers: a 1x4 header located at J1 and a 2x7 header at JP4. Integrated SoC for AP routers/ MIPS processor Now that we have full access to the board, we will identify the main chips and any headers or test points that can be suitable JTAG candidates. Remove the 4 screws located at the bottom of the device and then lever the device open by separating the top and bottom casing.Ĭarefully remove the antennas from the PCB if desired to have unrestricted access to the top and bottom of the PCB. The first step to locating JTAG is disassembling the device and gaining access to the PCB. ![]() Now that we have covered how JTAG works and its interface, let’s take a look at a TP-Link Archer C7 | AC1750 dual band wireless router to demonstrate how to locate and identify the pinout for JTAG. If you haven’t already, make sure to check out part one of the JTAG post where we provide background on the interface and its characteristics. ![]() Welcome back to our introduction to hardware hacking 101 series and our second installment of our JTAG blog post! In this post we share a teardown of a TP-Link AC1750 to demonstrate how to identify and verify a pinout for JTAG. ![]()
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