Convert Nokia N91 mechanical hard drive to USB flash drive

Teach you how to change the Nokia N91 mechanical hard drive into a USB flash drive. The Nokia N91 is the only mobile phone with a mechanical hard drive. The hard drive model MK4001MTD 4GB has an operating voltage of 3V and an operating current of 0.5A. It is produced by Toshiba and follows the MMC protocol. Without further ado, Let's start directly. First prepare an N91 hard drive, which must be easy to use. MMC protocol:
The picture above shows an mmc card. It has the same protocol as the Nokia N91 mechanical hard drive, that is, the mmc card can be read with a card reader, and the N91 machine hard drive is also the same.
The picture above shows the position of the hard disk of the N91 machine compared with the gold finger. You can see the same pins, but after careful observation, you find that the positions of the wide surface and the MMC card notch are somewhat different. At this time, it needs to be cut.
The picture above shows the position to be cut. Do not cut the red line to the PFC flexible cable. Feel free to cut the green line. (I have tried cutting it and it still works well.) Although the trace can be cut, it is ground There are traces in other locations, so it has no effect. Card reader chip selection: GL827, because it supports MMC protocol, SD protocol, etc. If you want to know more, you can find the official parameter manual.
   Note: I mentioned at the beginning that the working condition of the N91 machine hard disk is 3V 0.5A (that is, equal to 500MA). There is no MMC card, SD card, or TF card whose operating current can reach as high as 500MA. The maximum is around 10MA, which is tens of milliseconds. An is the biggest one. However, pin 2 of GL827 is used to power the card. It is impossible for the power supply current to be above 100MA. What should I do? Answer: Connect an external 3V power supply (provided by a voltage regulator) and leave pin 2 of GL827 floating. In this way, when the computer supplies 5V power to the circuit board, the voltage regulator supplies power to the N91 machine hard drive, and then to the GL827. Above circuit diagram:
      The picture is not very clear. It is recommended to look for the official circuit diagram of GL827. There are two 3-pin components in the lower left corner, which are two voltage regulators (note that they are powered by 3V). Leave the 2-pin of the chip unconnected. Yes, just follow the official circuit diagram of GL827. If you want to make a finished product, go to Lichuang eda. I will upload the project before December 20 (2022). If you want, you can directly download and proof PCB. If it's DIY, you can do it yourself. Some careful people have discovered that the locations of the MMC card and the N91 hard drive are different, and that is a matter of craftsmanship.
The picture above shows the place where the card holder needs to be cut. I tried several times before I succeeded. The size of the opening depends on the actual situation.
Pay attention to the position of the cable and card holder below. Since the MMC card is very thick and thin, it needs to be supported with an iron sheet or other things.
From the front view, solder the circuit board, apply conformal paint, let it dry for 24 hours, put in the shock-absorbing sponge, and install the shell (the shell is drawn by Lichuang Professional Edition).
Picture of the finished product After power-on test, the indicator light is on normally. If you put your hand on the case and there is vibration, it means it is working normally. When unplugging, be careful to pull it out gently to prevent vibration and damage to the hard disk.
    I use a desktop computer GL827 to complete the recognition and a large-capacity storage device.
      It can be recognized that this is a disk, but it shows no media description and few internal programs. At least the hardware description passes, and 70% to 80% of the time it is successful, the U disk is not recognized because there is no running program (code) in the hard disk of the N91 machine. I can't write. If anyone knows how to write, please leave a message.
   Ending: The above is all about changing the Nokia N91 mechanical hard drive into a USB flash drive. The one at the back was missing programs and was not easy to use. I forgot about it for a few months. It was only when I saw someone dismantling the N91 to take out the mechanical hard drive that I thought I would post a tutorial. The phone was released in 2006, and Ha and I were born in the same year.
                                December 10, 2022