• Locked Locked
  • Replies 6 replies
  • Subscribers 119 subscribers
  • Views 6466 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

[Cortex-M3] SWO Packet Parsing

Pietsuro Botsutoshi
Note: This was originally posted on 21st February 2012 at http://forums.arm.com

Hi,

I'm trying to play with SEGGER JLink device and ARM M3 micro in order to implement a SWV engine.
Currently I set a SWD protocol communication, and all other needed definitions for the SWO activation:

DEMCR    = 0x01000000
DWT_FUNCTION0 = 0x00000000
DWT_FUNCTION1 = 0x00000000
DWT_FUNCTION2 = 0x00000000
DWT_FUNCTION3 = 0x00000000

I would like to monitor a variable located at address 0x2000017C, a 2 bytes length interger that changes every 100us:

DWT_COMP0   = 0x2000017C
DWT_MASK0  = 0x00000001
DWT_FUNCTION0 = 0x00000023

SELECTED_PIN_PROTOCOL_REG = 0x00000002
TPIU_ACPR       = 0x0000008F
LOCK_ACCESS_REGISTER   = 0xC5ACCE55
ITM_TCR       = 0x0001000F
ITM_TPR       = 0x0000000F
ITM_TER       = 0x00000000
DWT_CTRL       = 0x400003FE
TPIU_FFCR       = 0x00000100

When I start my acquisition phase, I'm able to obtain the buffer content from the TPIU (see attachment):


00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 FC 00 00 00 05 8F 00 00 00 00 D0...

but I have difficulties regarding the parsing process: I'm not able to understand if the 28 bytes of 0s belong to the header that should terminates with only one 0b1.
The serie, in fact, terminates with 0xFC = 0b11111100, but I don't know if the first 1 bit (position [7]) belongs to the header definition, so if I have to discard it and consider the remaining value (0b1111100) value for the next data retrieving.

And after the header, how can I understand what type of info is following?

Thank you very much.
Parents
  • Note: This was originally posted on 13th April 2012 at http://forums.arm.com

    Hi there,

    Can you please let me know the way to decode those packets.
    My problem is: I am using Cortex M3 microcontroller and using Eclipse IDE (C/C++) for the same. So I want to display the debug messages in my code(printf). I am checking SWV and I cn see SWP packets in Jlink control panel.I am receiving data but I cant really comprehend it.
    Please advice.

    Thanks
    Sushant
Reply
  • Note: This was originally posted on 13th April 2012 at http://forums.arm.com

    Hi there,

    Can you please let me know the way to decode those packets.
    My problem is: I am using Cortex M3 microcontroller and using Eclipse IDE (C/C++) for the same. So I want to display the debug messages in my code(printf). I am checking SWV and I cn see SWP packets in Jlink control panel.I am receiving data but I cant really comprehend it.
    Please advice.

    Thanks
    Sushant
Children
No data