OpenOCD fails to connect with cortex processor

Question

I'm trying to flash a cortex m0 based SoC from a Raspberry Pi 3 Compute Module GPIOs but it keeps failing with the same error.

Error: Could not initialize the debug port

I'm following this https://learn.adafruit.com/programming-microcontrollers-using-openocd-on-raspberry-pi?view=all and this tutorials https://movr0.com/2016/09/02/use-raspberry-pi-23-as-a-jtagswd-adapter/. Compilation and install happens without issues.

The cortex m0 SoC is a Nordic Semiconductor nRF51822 bluetooth chip packaged in ISP1302 module.

The module GND and 3.3V are wired directly to the Compute module dev-kitand SWDCLK and SWDIO are wired on the GPIO 25, 24 as per tutorials. There's no connection for SRST or TRST.

The configuration file is as follows:

source [find interface/raspberrypi2-native.cfg]
bcm2835gpio_swd_nums 25 24
transport select swd

# target
source [find target/nrf51.cfg]

init
targets

(and I removed bcm2835gpio_srst_num 18 from the raspberrypi2-native.cfg)

executing with sudo openocd -f config.cfg

The raspberry Pi CM3 is running with the option core_freq=250 on /boot/config.txt and I need this option to reliably access UART1. I thought it could be something related to the clock, but not sure how to change/fix if it is.

I've tried several combinations of reset_config nothing changed the error. The full initialization stack is as follows:

Open On-Chip Debugger 0.10.0+dev-00111-gca9dcc8 (2017-04-24-15:30)
Licensed under GNU GPL v2
For bug reports, read
    http://openocd.org/doc/doxygen/bugs.html
BCM2835 GPIO nums: swclk = 25, swdio = 24
cortex_m reset_config sysresetreq
adapter speed: 1000 kHz
Info : BCM2835 GPIO JTAG/SWD bitbang driver
Info : SWD only mode enabled (specify tck, tms, tdi and tdo gpios to add JTAG mode)
Info : clock speed 1001 kHz
Info : SWD DPIDR 0x00150634
Error: Could not initialize the debug port
    TargetName         Type       Endian TapName            State       
--  ------------------ ---------- ------ ------------------ ------------
 0* nrf51.cpu          cortex_m   little nrf51.cpu          unknown

No matter what I tried I always get this "Error: Could not initialize the debug port".

Interesting enough, using a ST-Link/V2 adapter connected to the PI USB and modifying the interface on the configuration it works without issues.

Any suggestions? What am I doing wrong? Is there some initialization on the GPIO needed?

edit:

I've noticed someone voted to close the question as "unclear what's asking".

I'm asking: How can I connected the Raspberry Pi to a nRF51 SoC using its GPIO? Refer above everything I tried.

Answer 1

Not exactly the same configuration, but searching for pi3 on http://forum.doozan.com/read.php?3,21789,21927 reveals raspberry123-native.cfg, in which we find a change to the clockspeed:

# Please set the right peripheral_base address and Transition delay depending on which Raspi (1,2 or 3) you use.

interface bcm2835gpio

# Raspi2 and Raspi3 peripheral_base address

bcm2835gpio_peripheral_base 0x3F000000

# Raspi1 peripheral_base address
# bcm2835gpio_peripheral_base 0x20000000

# Transition delay calculation: SPEED_COEFF/khz - SPEED_OFFSET
# These depend on system clock, calibrated for stock 700MHz
# bcm2835gpio_speed SPEED_COEFF SPEED_OFFSET

# Raspi3 BCM2837 (1200Mhz):
bcm2835gpio_speed_coeffs 194938 48

# Raspi2 BCM2836 (900Mhz):
# bcm2835gpio_speed_coeffs 146203 36

# Raspi1 BCM2835: (700Mhz)
# bcm2835gpio_speed_coeffs 113714 28

Answer 2

1. • Problem: The probe is polling for an event which never gets set.

   • Solution: Might try scrapping the module and install another one which does work ok.

---

2. • Check which PI version you're using, this is a tutorial for programming microcontrollers using openocd on raspberry pi.

   • Note: that you would just use the string raspberrypi2-native instead of raspberrypi-native in the following cfg file. This was the openocd.cfg file I used:

---

source [find interface/raspberrypi-native.cfg]
transport select swd

bcm2835gpio_swd_nums 25 24
bcm2835gpio_srst_num 18

set CHIPNAME efm32
source [find target/efm32.cfg]

reset_config srst_nogate

adapter_nsrst_delay 100
adapter_nsrst_assert_width 100

init
targets
reset
reset halt
poll
flash probe 0
flash write_image erase emptyProject.hex
sleep 1
reset run
shutdown

---

• then run the command sudo openocd in the same directory as openocd.cfg. After that, my uC was programmed and LEDs were blinking.

• This was the wiring connection for the Raspberry Pi GPIO Header:

---

3.3V  - 3.3V   - pin 1
SWCLK - GPIO25 - pin 22
SWDIO - GPIO24 - pin 18
SRST  - GPIO18 - pin 12
GND   - GND    - pin 14

---

• in the directory containing your *.afx file (should be an output file in the same location as your build *.hex/*.bin), issue the command arm-none-eabi-gdb -ex "target remote localhost:3333" empty_project.axf -tui

• This should bring up a terminal based source code viewer and gdb console window.

• break empty_project.c:main.

• continue
• step...

---

3. As for a Tutorial for installing OpenOCD:

   • Make sure you have Raspberian installed on your PI.
   • Install the latest version of OpenOCD, by following this tutorial.
   • But specifically for the Pi you can just do the following:
     1. sudo apt-get update
     2. sudo apt-get install libtool libusb-dev libusb-1.0 autoconf automake texinfo
   • And then:
     1. git clone git://git.code.sf.net/p/openocd/code openocd-code
     2. cd openocd-code/
     3. ./bootstrap
     4. ./configure

   • This should spit out a bunch of stuff and then if everything worked you should see this at the end:

   • Make sure support for the programmer you are using is enabled, and then type make. Once that finishes, type sudo make install.

   • Now OpenOCD should be installed and ready to go!

4. Running OpenOCD:

   • Now you can run OpenOCD. For example, if you were using an F4 discovery board, you could so something like this:
   • sudo openocd -f board/stm32f4discovery.cfg
   • If it worked, you should see something like:
   • Info : stm32f4x.cpu: hardware has 6 breakpoints, 4 watchpoints
   • Which means your programmer is ready to go!

Note: I'm no expert, so I'm sure there's plenty left for me to figure out. On the other hand, I might do some digging to search for more. if this doesn't work, then I would recommend you to look into the chip itself or report the bug to the creators of the nRF51 SoC itself.