README.md

dap42

The dap42 project is an open-source firmware and hardware design for an inexpensive, minimalist CMSIS-DAP based debug probe based on the STM32F042F6 in a TSSOP-20 package.

This project is stable - it has been proven in the field by a few dozen users and all core functionality has been tested.

Current features

Firmware

• Serial Wire Debug (SWD) access over CMSIS-DAP 2.0 protocol via HID interface (tested with OpenOCD, LPCXpresso and pyOCD).
• CDC-ACM USB-serial bridge
• Device Firmware Upgrade (DFU) over USB (detach-only, switches to on-chip DFuSe bootloader).
• Serial Line CAN (SLCAN) interface - Silent mode, RX only.

Flash instructions

The default method to upload new firmware is via dfu-util. The Makefile includes the dfuse-flash target to invoke dfu-util. dfu-util automatically detaches the dap42 firmware and uploads the firmware through the on-chip bootloader.

To flash via another debugger, use make flash.

For detailed flashing instructions, see FLASHING.md

STM32F103

The dap42 firmware can also target the STM32F103 chip.

To build firmware for STLink/v2 knockoff designs, use the STM32F103 target or STM32F103-DFUBOOT target when using the dapboot bootloader. The CDC UART is connected to the SWIM pin (PB11) as an RX-only input.

To build firmware for the "bluepill" dev board, use the STM32F103-BLUEPILL or STM32F103-BLUEPILL-DFUBOOT targets.

The pin mapping is as follows:

Signal	Pin
SWDIO	PB14
SWCLK	PB13
RESET	PB0
TX	PA2
RX	PA3

Usage

OpenOCD

The dap42 firmware has been tested with gdb and OpenOCD on STM32F042 (of course), STM32F103, and LPC11C14 targets.

In general, the probe can be used with OpenOCD just by specifying the cmsis-dap interface:

openocd -f interface/cmsis-dap.cfg -f your_config.cfg -c "some inline command"

Example OpenOCD configurations can be found under the openocd/ folder.

MCUXpresso

The default probe detection rules used by MCUXpresso (formerly LPCXpresso) will not auto-discover generic CMSIS-DAP probes. To use the dap42 probe with MCUXpresso, you can modify the detection rules by editing probetable.csv in your MCUXpresso installation.

For MCUXpresso version 11.4 or newer, edit probetable.csv under ide/plugins/com.mcuxpresso.tools.bin.<...>/binaries/Scripts:

0x1209, 0xDA42, 64, 1, 0, 0, 0, "", 0x0000, -1, -1

In older versions, the CSV format has one fewer entry at the end:

0x1209, 0xDA42, 64, 1, 0, 0, 0, "", 0x0000, -1

USB-serial

Windows

On Windows 10, the serial port works without requiring additional configuration.

For Windows XP through Windows 7, the DAP42CDC.inf .inf file can be used to load the generic USB serial driver.

Mac OSX

On Mac OSX version 10.7 and later, the serial port should work without requiring any additional configuration.

Linux

On Linux, the serial port should be detected without requiring additional configuration. Depending on your distro settings, the modem manager may attempt to grab the serial port and use it as a modem. To prevent this, you can define a custom udev rule to ensure that the modem manager ignores the debugger.

ATTRS{idVendor}=="1209" ATTRS{idProduct}=="da42", ENV{ID_MM_DEVICE_IGNORE}="1"

Planned features

Firmware

• Additional CMSIS-DAP 1.10 features
• Serial Wire Output (SWO) trace support
• Additional CMSIS-DAP 2.0 features
• Bulk endpoints for higher throughput
• WebUSB compatibility

Hardware

• Simultaneous USB-serial bridge and SWO trace using an STM32F042K6 in an LQFP-32 package with both UARTs pinned out.
• Level-shifting/protective tri-state buffer between the probe and target SWD port.

Acknowledgements

The dap42 project was inspired by the Dapper Mime CMSIS-DAP proof-of-concept project.

The dap42 USB VID/PID pair is 1209/DA42, allocated through the pid.codes open-source USB PID program.

Licensing

All contents of the dap42 project are licensed under terms that are compatible with the terms of the GNU Lesser General Public License version 3.

Non-libopencm3 related portions of the dap42 project are licensed under the less restrictive ISC license, except where otherwise specified in the headers of specific files.

See the LICENSE file for full details.