isabella232 / free-dap

Free and open implementation of the CMSIS-DAP debugger firmware

Free-DAP

This is a free and open implementation of the CMSIS-DAP debugger firmware.

Only SWD protocol is supported for now. If you have a real need for JTAG support, please contact me.

Platform requirements

To create a CMSIS-DAP compliant debugger, your platform must:

• Implement USB HID device able to receive and send arbitrary reports
• Provide configuration file dap_config.h with definitions for hardware-dependent calls
• Call dap_init() at the initialization time
• Call dap_process_request() for every received request and send the response back

Configuration

For complete list of settings see one of the existing configuration file, they are pretty obvious.

To configure clock frequency you need to specify two parameters:

• DAP_CONFIG_DELAY_CONSTANT - clock timing constant. This constant can be determined by calling dap_clock_test() with varying parameter value and measuring the frequency on the SWCLK pin. Delay constant value is the value of the parameter at which output frequency equals to 1 kHz.
• DAP_CONFIG_FAST_CLOCK - threshold for switching to fast clock routines. This value defines the frequency, at which more optimal pin manipulation functions are used. This is the frequency produced by dap_clock_test(1) on the SWCLK pin. You can also measure maximum achievable frequency on your platform by calling dap_clock_test(0).

Your configuration file will need to define the following pin manipulation functions:

• DAP_CONFIG_SWCLK_TCK_write()
• DAP_CONFIG_SWDIO_TMS_write()
• DAP_CONFIG_TDO_write()
• DAP_CONFIG_nTRST_write()
• DAP_CONFIG_nRESET_write()
• DAP_CONFIG_SWCLK_TCK_read()
• DAP_CONFIG_SWDIO_TMS_read()
• DAP_CONFIG_TDI_read()
• DAP_CONFIG_TDO_read()
• DAP_CONFIG_nTRST_read()
• DAP_CONFIG_nRESET_read()
• DAP_CONFIG_SWCLK_TCK_set()
• DAP_CONFIG_SWCLK_TCK_clr()
• DAP_CONFIG_SWDIO_TMS_in()
• DAP_CONFIG_SWDIO_TMS_out()

Note that all pin manipulation functions are required even if one of the interfaces (JTAG or SWD) is not enabled.

Additionally configuration file must provide basic initialization and control functions:

• DAP_CONFIG_SETUP()
• DAP_CONFIG_DISCONNECT()
• DAP_CONFIG_CONNECT_SWD()
• DAP_CONFIG_CONNECT_JTAG()
• DAP_CONFIG_LED()