Note: Commercial use and mass production/sale are prohibited without permission!!!
-------------------------------------------------------- Divider --------------------------------------------------
Note: Do not remake if you do not have the firmware!!! Testing has shown that this controller, without firmware, can only read and write to a single card and cannot use DDR200 speed mode (160mb/s overclocking mode).
For those who want to experience it in advance, I have listed the GL3231 chip and Flash chip (with firmware already burned) on Xianyu. Click the link below to view.
Xianyu link: https://m.tb.cn/h.gN3Al7G?tk=lYe13fUar8NHU9046
"I have posted 【GL3231 chip overclocking card reader controller】 on Xianyu"
-------------------------------------------------------- Divider --------------------------------------------------
Previously, I made a GL3224 card reader, which used a USH-I overclocking card, but could not fully utilize the card's performance.
This is the GL3224 dual-card dual-reader: https://oshwhub.com/engineer_jiang/gl3224-du-ka-qi-_-shuang-ka-shuang-du
I've modified the GL3224 to support G2 board USB drives, EMCP221/EMMC153 + TF card dual reading: https://oshwhub.com/engineer_jiang/ji-yu-gl3224-qfn48-zhu-kong-emmc-du-xie-fang-an
This GL3231 card reader has been tested and the results are very good. It steadily manages the heat generated by the Kingston Blue Bar, but the downside is that the 4K speed isn't quite up to par.
-------------------------------------------------------- Divider --------------------------------------------------
Main Controller GL3231:
The GL3231 is a USB 3.1 Gen1 to dual SD 3.0 LUN Memory Card Reader controller. The GL3231 supports various SD memory cards, including Secure Digital™, SDHC, miniSD and microSD (T-Flash), MultiMediaCard™, RS-MMC, MMCmicro, and MMCmobile. It also supports high-density memory cards such as SDXC, high-speed memory cards, and SD 3.0 UHS-I (maximum capacity 2TB). The GL3231 also supports SANDISK EXTREME 160mb/s microSD UHS-I cards.
Commercially available products using the same controller include SanDisk Pro-Reader, Lexar RW310U, and RW310X.
The image below shows the speed test results of the SanDisk Pro-Reader card reader; the following text shows the test results of a custom-made card reader.

The custom-made card reader

features a modified side panel and a hidden SD/TF card design, resembling an Msata hard drive enclosure.


The PCB is shown in the image; the Type-C female connector is front-mounted and rear-mounted for a more secure fit, and all card slots are spring-loaded.
Read/Write Speed Test:
Test Conditions: Kingston Blue Stripe SDCG3 512G TF card, exFAT format; thermal paste was applied to both the controller chip and the TF card slot, allowing for close contact with the aluminum alloy casing; ambient temperature around 25℃, no active cooling.
1. AS SSD test
2. CrystalDiskMark test

Evaluation: Performed normally, as these are peak speeds.
3. ATTO test
4. urwtest full disk read/write test

Evaluation: Notably, there was no heat or speed reduction during full disk read/write, although the card reader casing became warm.
5. HD Tune 1G read/write test

Evaluation: The 1G write speed appears somewhat volatile; only one test was performed, so this is just for reference.
6. HD Tune 40G read/write test

Evaluation: The 40G read/write speed appears very stable with minimal fluctuations.