[Lenny400] Reviewing the Ingenic board initialisation code

Daniel Glöckner daniel-gl at gmx.net
Sun Jun 14 01:00:39 CEST 2015


On Tue, Jun 09, 2015 at 04:51:56PM +0200, Dr. H. Nikolaus Schaller wrote:
> > I did wonder whether it was even possible without opening up the Letux unit 
> > itself, and whether it would be possible even then. The NanoNote deliberately 
> > exposes a contact in the battery compartment for the hardware USB boot mode, 
> > meaning that even if U-Boot is broken or doesn't support the software USB boot 
> > mode (which appears to involve some initialisation of the SoC's bootloader, or 
> > maybe even a partial reimplementation of it), it's still possible to activate 
> > the hardware mode.
> 
> If you open the L400 it is possible to solder an RS232 adapter for console
> access. And it has a flex cable connector for JTAG.

The flex cable connector also carries the UART signals.
I just ordered a bunch of 24 pin 0.5mm flex cables for a few cents on
ebay. Maybe they fit.

According to an old version of the data sheet I once found on the net,
the JZ4730 can only boot from NAND flash on CS3 and NOR flash (or ROM
or EPROM) on CS0. CS0 is unused and available on TP100 directly under
the CPU, but I don't know the width of the data bus.

> It appears that the jz4730 has two USB1 host mode only ports (DPLS0/DNS0, DPLS1/DMNS1).

USB port 0 can act as a device. One of the first things start.S of
U-Boot does is to switch the port to host mode.

> One of the 4 ports is unused, two are the other two USB sockets and the last one goes
> to an CSC0101A-S16 PS2 converter (touch pad).

The port that is unused in the schematics is connected to the Wifi
controller in the Letux 400.

> None of the USB sockets has an ID pin - so they are not OTG capable.

Even though it can act as a device, I doubt it can do the special
OTG signaling for role reversal, etc.

Best regards,

  Daniel


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