Cannot communicate with Swan over USB

Hardware
1

Problem

If you connect the Swan via USB to your computer, and the computer doesn’t recognize the Swan as a USB device or a serial port. In addition, the Swan does not seem to enter the “bootloader” mode when holding the BOOT button while tapping the RESET button

Cause

This may be from the option bytes on the STM32L4 processor on the Swan being set incorrectly.

Resolution

Required Tools:

  • STM32CubeProgrammer installed (including the command line interface (CLI)
  • STLink Debugger
  • Micro-USB cable for power

Procedure

Option 1 - Update options bytes in flash from STM32CubeProgrammer IDE: Swan Quickstart - Blues Wireless Developers

Option 2 - Update option bytes using CLI with the steps listed below.

WARNING: This will erase the flash on the Swan

  1. Connect the STLink Debugger to the Swan with the included ribbon cable and your computer via USB
  2. Apply power to the Swan via the micro USB port and plug into your computer (or other USB power source)
  3. Open the Windows Command window
  4. Go to the STM32CubeProgrammer bin folder
cd "C:\Program Files (x86)\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin"
  1. Apply the following commands in this order
STM32_Programmer_CLI --connect port=SWD --optionbytes RDP=0xBB

STM32_Programmer_CLI --connect port=SWD --optionbytes RDP=0xAA

STM32_Programmer_CLI --connect port=SWD --optionbytes nRST_STOP=1 IWDG_SW=1 IWDG_STOP=1 IWDG_STDBY=1 WWDG_SW=1 DBANK=1 nBOOT1=1 SRAM2_PE=1 SRAM2_RST=1 nSWBOOT0=01 PCROP1_STRT=0x1FFFF PCROP1_END=0x10000 WRP1A_STRT=0xFF WRP1A_END=0 WRP1B_STRT=0xFF WRP1B_END=0

STM32_Programmer_CLI --connect port=SWD --optionbytes PCROP_RDP=1
  1. Verify the option byte values by displaying them to the command prompt
STM32_Programmer_CLI --connect port=SWD --optionbytes displ

Compare the response to Expected Option Byte Config below

  1. Unplug and re-plug into the Swan micro USB port using a USB cable from the Swan to your computer

If you are still experiencing difficulties, please contact Blues Support

Expected Option Byte Config

C:\Program Files\STMicroelectronics\STM32Cube\STM32CubeProgrammer\bin>STM32_Programmer_CLI --connect port=SWD --optionbytes displ
      -------------------------------------------------------------------
                       STM32CubeProgrammer v2.8.0
      -------------------------------------------------------------------

ST-LINK SN  : 0036000D5553500920393256
ST-LINK FW  : V3J7M2
Board       : STLINK-V3MINI
Voltage     : 3.29V
SWD freq    : 24000 KHz
Connect mode: Normal
Reset mode  : Software reset
Device ID   : 0x470
Revision ID : Rev W
Device name : STM32L4Rxxx/STM32L4Sxxx
Flash size  : 2 MBytes
Device type : MCU
Device CPU  : Cortex-M4
BL Version  : 0x__


UPLOADING OPTION BYTES DATA ...

  Bank          : 0x00
  Address       : 0x40022020
  Size          : 20 Bytes

██████████████████████████████████████████████████ 100%

  Bank          : 0x01
  Address       : 0x40022044
  Size          : 16 Bytes

██████████████████████████████████████████████████ 100%


OPTION BYTES BANK: 0

   Read Out Protection:

     RDP          : 0xAA (Level 0, no protection)

   BOR Level:

     BOR_LEV      : 0x0 (BOR Level 0, reset level threshold is around 1.7 V)

   User Configuration:

     nRST_STOP    : 0x1 (No reset generated when entering Stop mode)
     nRST_STDBY   : 0x0 (Reset generated when entering Standby mode)
     nRST_SHDW    : 0x0 (Reset generated when entering the Shutdown mode)
     IWDG_SW      : 0x1 (Software independant watchdog)
     IWDG_STOP    : 0x1 (IWDG counter active in stop mode)
     IWDG_STDBY   : 0x1 (IWDG counter active in standby mode)
     WWDG_SW      : 0x1 (Software window watchdog)
     BFB2         : 0x0 (Dual-bank boot disable)
     DBANK        : 0x1 (Dual bank mode with 64 bits data)
     nBOOT1       : 0x1 (Boot from system memory when BOOT0=1)
     SRAM2_PE     : 0x1 (SRAM2 parity check disable)
     SRAM2_RST    : 0x1 (SRAM2 is not erased when a system reset occurs)
     nSWBOOT0     : 0x1 (BOOT0 taken from PH3/BOOT0 pin)
     nBOOT0       : 0x1 (BOOT0 = 0, boot from system memory when nSWBOOT0=1 and main flash is empty,otherwise, boot from main flash memory)

   PCROP Protection (Bank 1):

     PCROP1_STRT  : 0x1FFFF  (0x80FFFF8)
     PCROP1_END   : 0x10000  (0x8080000)
     PCROP_RDP    : 0x1 (PCROP zone is erased when RDP is decreased)

   Write Protection (Bank 1):

     WRP1A_STRT   : 0xFF  (0x80FF000)
     WRP1A_END    : 0x0  (0x8000000)
     WRP1B_STRT   : 0xFF  (0x80FF000)
     WRP1B_END    : 0x0  (0x8000000)
OPTION BYTES BANK: 1

   PCROP Protection  (Bank 2):

     PCROP2_STRT  : 0x1FFFF  (0x81FFFF8)
     PCROP2_END   : 0x10000  (0x8180000)

   Write Protection (Bank 2):

     WRP2A_STRT   : 0xFF  (0x81FF000)
     WRP2A_END    : 0x0  (0x8100000)
     WRP2B_STRT   : 0xFF  (0x81FF000)
     WRP2B_END    : 0x0  (0x8100000)
1 Like
2

Hi @gwolff,

I’ve had this problem on both the Swan and just yesterday on a Cygnet I just receive to test. I think I caused the problem on the Cygnet when I tried uploading a simple blink sketch without changing the Board Part Number from Swan R5 to Cygnet in the Arduino IDE. I have no idea what’s caused the issue on the Swan, but fortunately it hasn’t happened very often.

But I was happy to find this post and be able to recover both the Swan and the Cygnet by updating the checkboxes in the User Configuration section Programmer (your option 1 - using the STLINK). Some of the addresses in the lower sections of the Expected Option Byte Config list don’t match, but I left them alone for the moment. Three actual questions:

(1) Is the Expected Option Byte Config identical for both the Swan and Cygnet. I’m assuming the Cygnet could be different, and if so, could you please post those as well?

(2) The link in the post above for Option 1 to the Swan QuickStart using the STLINK and Programmer doesn’t seem to lead to anything specific to this problem, just the general description of using the STMCubeIDE for programming. Is that right, or am I missing something important there?

(3) Is there an easy way to output Option Byte settings from the STMCubeProgrammer? I’d like the capture all the settings for before and after so I have a documented point of reference. You show that list in your post but it looks like it came from the CLI option.

3

IRT my question #3 – NM – I found the option to export the settings, under the dropdown box that defaults to Read…but can be changed to Export current MCU OptionBytes.

OptionBytesExportDropdown
OptionBytesExportDropdown1920×1108 201 KB