Few days ago I disassembled my Elonex 621EB ebook reader and found the pinout of the serial port, which allows me to access bootloader (U-Boot) and the terminal of the system. Since then I’ve been studying embedded linux development (not just basic programming, but also bootloader and kernel development).
I’ve found toolchain for the processor of my ebook reader (s3c2440). I tried to compile U-boot with tutorial found in the internet. I used exactly same source, commands and arguments to compile the U-boot. I wrote it to NAND-flash and more or less surprisingly it didn’t work. Now my e-paper ebook reader is more paper-like than ever: blank white plate. Luckily I think I dumped U-Boot part of the Nand and I have it in my HDD.
Without bootloader I don’t have a serial terminal anymore and therefore I have to program the U-Boot to Nand with JTAG. After about an hour of searching I found a wiki page which has pinout for JTAG header. There’s also a serial port pinout. Serial port was fun to look for, but JTAG pinout is too hard to figure out by testing, if there is easier alternative. 600EB is little bit different than 621EB, but I’m feeling that the JTAG pinout is same in both 600EB and 621EB. I’ll probably make a parallel port JTAG -cable or pic18f2550 based USB JTAG -cable. Maybe I’ll finally make a pcb for my xc9572xl CPLD and play with it too.
After finding that JTAG pinout, I’m more confident that I can make this ebook reader work again. We’ll see if that is going to happen.