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Old 01-06-2019, 08:03 PM   #14
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Join Date: Jul 2015
City & State: Porto
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Default Re: Tools / technique for boards with eMMC repair?

Originally Posted by CapLeaker View Post
any pictures to go with this?
Originally Posted by CapLeaker View Post
There are some main boards (for example Vizio's) with an eMMC. They also feature a nice UART and JTAG hookup. Anyone ever tried to gain access or flash that eMMC through that provided JTAG port?
The JTAG port is connected to the main processor. Therefore to gain access to the flash thru the JTAG port you must first obtain access to the main processor using the JTAG port.
The greatest problem being that’s usually confidential stuff (or must crawl the released code, if any, and figure out how to properly initialize it to successfully hook its JTAG port).
It’s making things harder than they could and should be!

It’s easy to find some nice pictures for an eMMC153/169-SD Adapter FBGA153 BGA169 to a SD Adapter (e.g.: link)

To make things even easier you can hook wires from the circuit board to an empty SD card, see images attached.
[Connect VCC and VCCQ to the correct voltage levels]
1. In 1 bit mode & SPI mode - pin 1 (DAT3/CS) is not used.
2. Since SD readers operate at 3.3V, if VCCQ is tied up in circuit to 1.8V then use a low voltage adapter to convert 3.3v signals into 1.8v logic level.
3. Most often the CPU may attempt to communicate with the eMMC while your’re reading / writing it. Here’s where the JTAG port comes handy to quickly identify the RST line and hold the CPU it in reset mode.
Attached Images
File Type: png eMMC Default FBGA153 Pinout.png (243.5 KB, 18 views)
File Type: png eMMC Full Default FBGA153 BGA169 Pinout.png (108.5 KB, 13 views)
File Type: png eMMC SD Card Mode -vs- SPI Mode.png (26.0 KB, 9 views)

Last edited by megaraider; 01-06-2019 at 09:11 PM.. Reason: Added "Notes"
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