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Possible bug in memory access code

#1
Hi All,

I have an old but fully functional SMC WEBT-G access point I'm trying to rework a bit. My plan is to upgrade its flash to 8 MB (done already, works fine) and RAM to 32 MB and then install some flavor of Linux on it (most likely OpenWrt).

I bought a BlackcatUSB device some weeks ago to be able to program the flash in case I ruin the bootloader (which I've done already once) but it looks like I'm unable to use it for flash programming through the EJTAG port of my device. :(

The board uses an Atheros AR5315 chipset and has an EJTAG 2.6 compatible JTAG interface so I guess it should be supported through the Atheros SPI-over-JTAG API (in fact, I spent many hours already checking the methods and register addresses - the API should work fine with this SoC).

According to the console output, everything seems to be in order (connecting to the device, resetting the CPU and peripherals, entering debug mode) but as soon as I try to read from or write to the RAM, I get strange results:

fcusb1.png
fcusb2.png

As it's easy to see, some parts of the uploaded data keeps repeating until the end of memory. Also, in case I try to read or write a register through JTAG.Poke/Peek, I get no useful data, just zeroes everytime, regardless the memory address I try to access.

Also (might be related to the issue above), in case I try to access the flash using the Atheros API, I get no results at all, the SPI control register returns zero all the time, not even the chip ID process works:

fcusb3.png

Any idea why this happens? I'd be more than happy if I could use my FCUSB to program flash through JTAG (that's why I bought it), soldering jumper wires to the flash chip every time would be so inconvenient and dumb while I have a JTAG header soldered to the PCB already...

I've attached the script I'm using for reference - it doesn't contain too much interesting stuffs, though.

Hope someone can assist me as I'm totally stuck now... :(

Thanks in advance!

Regards,
Gergely
 

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