SWDscan

This Arduino-based Platformio project allows quick identification of SWD ports.

How does it work?

The app iterates through microcontroller gpio pins following the definition specified using PIN_MASK to find SWD clock and io lines. Pins are enabled by setting corresponding bits of PIN_MASK, i.e. pins 2-8 are enabled for PIN_MASK of 0b111111100 or 0x1fc.

Besides PIN_MASK predefined at build time you can also set the pin mask at runtime using the m command. Entering 508 or 0x1fc will result in pin_mask set to 0b111111100 so you can update the configuration without the need to rebuild the project.

How to use it?

• hook up your Arduino to the target
• use a logic level shifer between Arduino and target if required
• optionally adjust PIN_MASK for your setup, can be done later
• select proper build target
• build the project and upload it to your board
• establish serial connection with baud rate of 115200
• ammend debug options if required
• use option m to set a pin mask at runtime
• use option h for help
• use option e to enumerate pins

How to configure it?

• m - pin mask set at runtime - select which MCU GPIO pins to check for SWD IO and CLK lines, value can be provided as either a decimal or hexadecimal integer up to 64 pins, pin X is enabled by setting a bit at position X to 1 in the pin mask, pin 0 is of least significance, for example 0x3 enables pins 0 and 1, 0xff enables pins 0 to 7 and 0xfc enables pins 2 to 7

• d - debug level - defaults to normal

  • normal - prints information for each tested combination
  • quiet - prints information only for positive hits
  • verbose - prints bit patterns set and received on the IO line

• b - break on hit - defaults to true

  • true - search is stopped when positive hit is found
  • false - search is continued despite positive hit is found

What is test mode for?

Test mode allows to check if target SWD IO and CLK lines are connected to specified pins.

How does it look like?

• help menu

> h
+-------------------------------------------+
|                   SWDScan                 |
+-------------------------------------------+
 e - enumerate swd lines
 m - set pin mask, current: 0x1C
 t - test pin pair for swd
 b - break on hit, current: 1
 d - set debug level, current: 1
 h - this help
+-------------------------------------------+

• swd enumeration with debug level 1 on a BluePill

> d
Choose debug level 0-2 1
Debug set to 1
> e
+-------------------------------------------+
| CLK PIN | IO PIN | ACK | PART NO | MAN ID |
+-------------------------------------------+
|    2    |    3   |  7  |   ffff  |   7ff  |
|    2    |    4   |  7  |   ffff  |   7ff  |
|    3    |    2   |  1  |   ba01  |   23b  |
|    3    |    4   |  7  |   ffff  |   7ff  |
|    4    |    2   |  7  |   ffff  |   7ff  |
|    4    |    3   |  7  |   ffff  |   7ff  |
+----------------- SUCCESS -----------------+

• swd enumaration with pin mask set at runtime

> m
Enter pin mask 0xfc
Pin mask set to 11111100
> b
Break work on hit? 1/0 1
> d
Choose debug level 0-2 1
Debug set to 1
> e
+-------------------------------------------+
| CLK PIN | IO PIN | ACK | PART NO | MAN ID |
+-------------------------------------------+
|    2    |    3   |  7  |   ffff  |   7ff  |
|    2    |    4   |  7  |   ffff  |   7ff  |
|    2    |    5   |  7  |   ffff  |   7ff  |
|    2    |    6   |  7  |   ffff  |   7ff  |
|    2    |    7   |  7  |   ffff  |   7ff  |
|    3    |    2   |  1  |   ba01  |   23b  |
+----------------- SUCCESS -----------------+

• test response on lines 3 and 2 with debug level 1 (valid connection, read part no is 0xba01)

> t
Enter SWD CLK PIN NO 3
Enter SWD IO PIN NO 2
+-------------------------------------------+
| CLK PIN | IO PIN | ACK | PART NO | MAN ID |
+-------------------------------------------+
|    3    |    2   |  1  |   ba01  |   23b  |
+----------------- SUCCESS -----------------+

• test response on lines 2 and 3 with debug level 1 (invalid connection, read part no is 0xffff)

> t
Enter SWD CLK PIN NO 2
Enter SWD IO PIN NO 3
+-------------------------------------------+
| CLK PIN | IO PIN | ACK | PART NO | MAN ID |
+-------------------------------------------+
|    2    |    3   |  7  |   ffff  |   7ff  |
+----------------- FAILURE -----------------+

Nothing found?

In case the target fails to switch to SWD mode:

• put the target into reset state
• put the target into bootloader mode (bootN pins)
• ensure common ground is present between scanner board and target

No Platformio?

No problem, just copy the contents of src/main.cpp to a new Arduino project, remove the Arduino.h import from the first line and you're ready to go.

Need JTAG?

Check JTAGscan to identify JTAG TMS, TCK, TDO and TDI pins.