JTAG

From linux-sunxi.org
Jump to: navigation, search
µSD breakout showing 14pin JTAG connector

Initial notes:

  • JTAG over Microsd
  • Below is default setup (A10) at boot! Bootloader etc may change it
  • Only tested with a microsd breakout board designed for a10
  • microsd breakout seems to have specific pull-ups/pull-downs in the board
  • I will test with direct connection to microsd pins later.
  • This has been tested on an MK802 only, but should theoretically work for everything.
  • This has been confirmed working on an A13 Tablet as well.
Microsd Pin JTAG Connection 14-pin ARM JTAG Header
Data2 1 TCK 9
Cmd 3 TDO 11
Data0 7 TDI 5
Data1 8 TMS 7
VDD 4 VTG 1,13
GND 6 GND  2,3,4,6,8,10,12,14

It is important to make sure boot0/boot1/u-boot/kernel doesn't pinmux this away, so nothing else must be using the pins. The script.bin needs to contain a correct jtag_para section. On my device, the default script.bin seems to contain an invalid configuration for the ports in question. Below is the configuration matching the working JTAG!

[jtag_para]
jtag_enable = 1
jtag_ms = port:PF00<4><default><default><default>
jtag_ck = port:PF05<4><default><default><default>
jtag_do = port:PF03<4><default><default><default>
jtag_di = port:PF01<4><default><default><default>

I used a Dangerous Prototypes Bus Blaster V2(.5) for my experiments (http://dangerousprototypes.com/docs/Bus_Blaster). I'm using the default buffer, which makes it jtagkey compatible. For now, i've only verified that both UrJTAG and OpenOCD can detect a device over the JTAG connection, but I haven't managed to read/write from memory yet or anything else fancy.

Some output: UrJTAG detect:

jtag> detect
IR length: 4

Chain length: 1

Device Id: 01001011101000000000010001110111 (0x4BA00477)

  Unknown manufacturer! (01000111011) (/usr/local/share/urjtag/MANUFACTURERS)

UrJTAG discovery:

jtag> discovery
Detecting IR length ... 4
Detecting DR length for IR 1111 ... 1
Detecting DR length for IR 0000 ... 1
Detecting DR length for IR 0001 ... 1
Detecting DR length for IR 0010 ... 1
Detecting DR length for IR 0011 ... 1
Detecting DR length for IR 0100 ... 1
Detecting DR length for IR 0101 ... 1
Detecting DR length for IR 0110 ... 1
Detecting DR length for IR 0111 ... 1
Detecting DR length for IR 1000 ... 35
Detecting DR length for IR 1001 ... 1
Detecting DR length for IR 1010 ... 35
Detecting DR length for IR 1011 ... 35
Detecting DR length for IR 1100 ... 1
Detecting DR length for IR 1101 ... 1
Detecting DR length for IR 1110 ... 32


Extremely work in progress OpenOCD cfg:

sun4i.cfg

Tested OpenOCD features:

  • dumping memory (sun4i.cpu mdw commands)
  • halt & resuming
  • gdb
    • Loading files (tested with fel-pio)
    • Single-stepping lines/instructions through loaded programs
    • Breakpoints

See also

Personal tools
Namespaces

Variants
Actions
Navigation
Tools