I have sent otaku a copy of the bios dump i made from my E2 emailer. I also had an idea for recovery of the bios of the E3, has anyone yet worked out if the Jtag port of the CPU in the E3 is taken to a usable header on the e3's board. According to the datasheet for the e3's cpu the jtag pins are at locations U15, U16, U17, T14 and R13 (the jtag signals are called (nTrst, TDO, TDI, TMS and TCK off hand i cant rember which pin is which)
If these pins are routed to a suitable set of test points it should be relatively easy (if time consuming) to dump the bios of the E3 using an inexpensive (�10ish) wiggler type jtag interface. This site has details of how to build a cheap wiggler compatible buffered jtag lead, http://jtag-arm9.sourceforge.net/ , however there are several places selling these interface for around a tenner (although these dont include the transistor for control of the nTrst line) since jtag leads have just become a popular way to read data off some other UK equipment.
Dumping of the bootloader could then be done using either macraigors , http://www.macraigor.com/ , flashprog (the demo will read but not write the flash) or the long winded method using ocd commander and a macro to read each byte then converting the log of this macro to a binary file (which was how I dumped the E2 bios as i hadnt sussed flashprog :)
If the E3 behaves like the E2 did it will have its WDT enabled and locked so about 4 or 5 seconds after you halt the CPU the WDT will time out and reset the box, this resulted in the memory controller being in its boot up state with the bios (on chip select 0) being mapped throught the whole of memory, reading past the end of the bios chip just looped back to the beginning of the chip. Because the WDT was enabled I was unable to get a dump of the ram from a running box so i couldnt recover the uncompressed firmware image from ram. I am interested in getting an E3 to play with but unfortunately time and money are not on my side at the moment, but if i do i will look at dumping the E3 bios too (and ram if WDT is not enabled) Just a word of warning, dont use a jtag interface that doesnt have a 74hc244 or ac244 chip as i dont think arm cores are 5v tolerant so the simple resistor based jtag leads may well kill the CPU.
I think the jtag interface from tailor-madecircuits, http://www.tailor-madecircuits.com/jtag_interface.htm , should work for dumping the bios but it doesnt have the nTrst circuitry, but I think it will work, but be warned TMC have had a run on these so there is a bit of a delay on them.
Obviously all of this will only be of use if the jtag signals have been routed to somewhere usefull on the E3's board.
en4rab
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Hi en4rab,
If the E3 behaves like the E2 did it will have its WDT enabled and locked so about 4 or 5 seconds after you halt the CPU the WDT will time out and reset the box
Code to reset the watch-dog's timer writes 0x0000a5a5 to 0xffff8004.
e3a0c9fe mov r12, #&3f8000 e24cc501 sub r12, r12, #&400000 # r12 = 0xffff8000 = WDT. e3a030a5 mov r3, #&a5 e2833ca5 add r3, r3, #&a500 # r3 = 0xa5a5. e58c3004 str r3, [r12, #4] # wdtcntr.
Presumably, something similar could be done with JTAG to disable the WDT completely?
Cheers,
Ralph.
Hi en4rab,
I also had an idea for recovery of the bios of the E3, has anyone yet worked out if the Jtag port of the CPU in the E3 is taken to a usable header on the e3's board.
Or to some test pads immediately underneath the OMAP5910 SoC? If anyone does have their E3 in bits, a photograph of the top and bottom of the main PCB good enough to read IC lettering would be helpful. Using a flat-bed scanner can be a good way to achieve this, but make sure not to scratch the glass.
According to the datasheet for the e3's cpu the jtag pins are at locations U15, U16, U17, T14 and R13 (the jtag signals are called (nTrst, TDO, TDI, TMS and TCK off hand i cant rember which pin is which)
Signal GZG GDY Ball Ball TCK W18 T14 TDI Y19 U17 TDO AA19 U16 TMS V17 R13 /TRST Y18 U15
I think the jtag interface from tailor-madecircuits, http://www.tailor-madecircuits.com/jtag_interface.htm , should work for dumping the bios but it doesnt have the nTrst circuitry, but I think it will work, but be warned TMC have had a run on these so there is a bit of a delay on them.
Thanks for the URL, I wasn't aware of them.
Cheers,
Ralph.
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en4rab -
Ralph Corderoy