Using JTAG UART

Xilinx® System Debugger Command-line Interface (XSDB) supports virtual UART through Jtag, which is useful when the physical Uart doesn't exist or is non-functional. To use Jtag UART, the SW application should be modified to redirect STDIO to the Jtag UART. Xilinx SDK provides a CoreSight driver to support redirecting of STDIO to virtual Uart, on ARM based designs. For MB designs, the uartlite driver can be used. To use the virtual Uart driver, open board support settings in Xilinx SDK and can change STDIN / STDOUT to coresight/mdm.

XSDB supports virtual UART through two commands.

• jtagterminal - Start/Stop Jtag based hyper-terminal. This command opens a new terminal window for STDIO. The text input from this terminal will be sent to STDIN and any output from STDOUT will be displayed on this terminal.
• readjtaguart - Start/Stop reading from Jtag Uart. This command starts polling STDOUT for output and displays in on XSDB terminal or redirects it to a file.

Below is an example XSCT session that demonstrates how to use a JTAG terminal for STDIO.

connect
source ps7_init.tcl
targets -set -filter {name =~"APU"}
loadhw system.hdf
stop
ps7_init
targets -set -nocase -filter {name =~ "ARM*#0"}
rst –processor
dow <app>.elf
jtagterminal
con
jtagterminal -stop #after you are done  

Below is an example XSCT session that demonstrates how to use the XSCT console as STDOUT for JTAG UART.

connect
source ps7_init.tcl
targets -set -filter {name =~"APU"}
loadhw system.hdf
stop
ps7_init
targets -set -nocase -filter {name =~ "ARM*#0"}
rst –processor
dow <app>.elf
readjtaguart
con
readjtaguart -stop #after you are done

Below is an example XSCT session that demonstrates how to redirect the STDOUT from JTAG UART to a file.

connect
source ps7_init.tcl
targets -set -filter {name =~"APU"}
loadhw system.hdf
stop
ps7_init
targets -set -nocase -filter {name =~ "ARM*#0"}
rst –processor
dow <app>.elf
set fp [open uart.log w]
readjtaguart -handle $fp
con
readjtaguart -stop #after you are done