Running GDB with SES and nRF52840DK

[kw_martin]

RTT seems to be mostly working using the viewer with the command:

JLinkRTTViewer -device nRF52840_xxAA

It seems I need to re-connect each time I start a debug from SES, but this is okay. What I really need thought is to get gdb communicating during a debug. Starting with the command:

JLinkGDBServer -device nRF52840_xxAA -endian little -if SWD -speed 400kHz

seems to connect but then hangs without a prompt, and I can't run any gdb commands, anything typed in the window has no effect. I running under Ubuntu 18.04

> uname -a
Linux granite10192.168.1.23 4.15.0-101-generic #102-Ubuntu SMP Mon May 11 10:07:26 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux

SEGGER J-Link GDB Server V6.73b (beta) Command Line Version

JLinkARM.dll V6.73b (DLL compiled May 15 2020 17:24:15)

Command line: -device nRF52840_xxAA -endian little -if SWD -speed 400kHz
-----GDB Server start settings-----
GDBInit file:                  none
GDB Server Listening port:     2331
SWO raw output listening port: 2332
Terminal I/O port:             2333
Accept remote connection:      yes
Generate logfile:              off
Verify download:               off
Init regs on start:            off
Silent mode:                   off
Single run mode:               off
Target connection timeout:     0 ms
------J-Link related settings------
J-Link Host interface:         USB
J-Link script:                 none
J-Link settings file:          none
------Target related settings------
Target device:                 nRF52840_xxAA
Target interface:              SWD
Target interface speed:        400kHz
Target endian:                 little

Connecting to J-Link...
J-Link is connected.
Firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Mar 17 2020 14:43:00
Hardware: V1.00
S/N: 683455871
Feature(s): RDI, FlashBP, FlashDL, JFlash, GDB
Checking target voltage...
Target voltage: 3.30 V
Listening on TCP/IP port 2331
Connecting to target...
Connected to target
Waiting for GDB connection...

[kw_martin]

Something is not going right. Sometimes it seems to work, most of the time not. For example:

1)

• Debug -> Debugger -> Target Connection to "GDB Server"
• Debug -> GDB Server -> Type to "J-Link"

2) In one termal:

> JLinkGDBServer -device nRF52840_xxAA -endian little -if SWD -speed 400kHz
SEGGER J-Link GDB Server V6.73b (beta) Command Line Version

JLinkARM.dll V6.73b (DLL compiled May 15 2020 17:24:15)

Command line: -device nRF52840_xxAA -endian little -if SWD -speed 400kHz
-----GDB Server start settings-----
GDBInit file:                  none
GDB Server Listening port:     2331
SWO raw output listening port: 2332
Terminal I/O port:             2333
Accept remote connection:      yes
Generate logfile:              off
Verify download:               off
Init regs on start:            off
Silent mode:                   off
Single run mode:               off
Target connection timeout:     0 ms
------J-Link related settings------
J-Link Host interface:         USB
J-Link script:                 none
J-Link settings file:          none
------Target related settings------
Target device:                 nRF52840_xxAA
Target interface:              SWD
Target interface speed:        400kHz
Target endian:                 little

Connecting to J-Link...
J-Link is connected.
Firmware: J-Link OB-SAM3U128-V2-NordicSemi compiled Mar 17 2020 14:43:00
Hardware: V1.00
S/N: 683455871
Feature(s): RDI, FlashBP, FlashDL, JFlash, GDB
Checking target voltage...
Target voltage: 3.30 V
Listening on TCP/IP port 2331
Connecting to target...
Connected to target
Waiting for GDB connection...

3) My .gdbinit file:

define hlt
  monitor reset
end
define ld
  file pca10056/blank/ses/Output/Debug/Exe/twi_sensor_pca10056.elf
end
alias dsc=disconnect
alias to=advance
ld
target remote localhost:2331
hlt

4) In second terminal:

> arm-none-eabi-gdb
GNU gdb (7.10-1ubuntu3+9) 7.10
Copyright (C) 2015 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <gnu.org/.../gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "--host=x86_64-linux-gnu --target=arm-none-eabi".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<www.gnu.org/.../>.
Find the GDB manual and other documentation resources online at:
<www.gnu.org/.../>.
For help, type "help".
Type "apropos word" to search for commands related to "word".
0x00005798 in TMP117_write_reg (pntr=0 '\000', val=60)
    at /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c:174
174    ret_code_t TMP117_write_reg(uint8_t pntr, uint16_t val) {
Resetting target
(gdb)

5)

There should not be a breakpoint at line 174? This is left over from something previous, I will now try and clear all break points, put a single breakpoint at the beginning of main() in main.c and stop there

(gdb) del
(gdb) b
Breakpoint 1 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb) del
Delete all breakpoints? (y or n) y
(gdb) b
Breakpoint 2 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb)

6)

Note, the breakpoint can't be deleted. The two attempts have different replies, but the breakpoint still remains. I will now try and reset again, and clear all breakpoints

(gdb) b
Breakpoint 1 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb) del
Delete all breakpoints? (y or n) y
(gdb) b
Breakpoint 2 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb) hlt
Resetting target
(gdb) b
Note: breakpoint 2 also set at pc 0x5798.
Breakpoint 3 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb) del
Delete all breakpoints? (y or n) y
(gdb) b
Breakpoint 4 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb)

Still can't delete it,

(gdb) cl 174
Deleted breakpoint 4
(gdb) b
Breakpoint 5 at 0x5798: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 174.
(gdb)

Still can't delete it. Let's try and put a breakpoint at the beginning of main and stop there

(gdb) b main
Breakpoint 6 at 0x5b4c: file /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c, line 359.
(gdb) c
Continuing.

Breakpoint 5, 0x00005798 in TMP117_write_reg (pntr=0 '\000', val=60)
    at /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c:174
174    ret_code_t TMP117_write_reg(uint8_t pntr, uint16_t val) {
(gdb)

It skipped the breakpoint at the beginning of main and kept going until the breakpoint at line 174, and bt doesn't work.

(gdb) bt
#0  0x00005798 in TMP117_write_reg (pntr=0 '\000', val=60)
    at /home/martin/Dropbox/Nordic/SDK/Workspace/Peripheral/twi_sensor/main.c:174
#1  0x1a2e058a in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)
(gdb)

Some other questions: I need gdb so I can do the equivalent of calling a function at a breakpoint. Is it possible to do something like this directly in SES using jlink rather than GDB Server? I see there is a debug window, but it doesn't respond to gdb like commands.

Second question, running SES with jlink, I can see variables in the local window, and I can see some variables in the global window, but I can't see my static global variables in the global window, although when I hover over them with the mouse, I can see their values.

Finally, have I missed some documentation that explains how to use gdb with SES, the Segger documentation has almost no information.

When I quite everything, and started back up, the break point situation seemed to get better. But when I changed the code, and rebuilt the binary, the break points stopped working correctly again. It looks like there is something going wrong with the GDB Server and running gdb (at least to me).

[Håkon Alseth]

Hi,

 

My apologies for the late response

For the questions related to segger embedded studio, and the advanced debugging features you're trying to do, I would recommend that you contact Segger directly and ask them, as they have more knowledge about their products than we do.

 

kw_martin said:

Some other questions: I need gdb so I can do the equivalent of calling a function at a breakpoint

This is possible in gdb. Please see this thread: https://devzone.nordicsemi.com/f/nordic-q-a/24081/call-function-from-gdb-at-breakpoint

If you think there's any breakpoints present, you can list these in gdb by entering "info b". I suspect that you are halting the CPU at certain points in time, thus you see it running on different stages of your firmware.

 

Kind regards,

Håkon