boards:riscv:hpm6750evk2: revised README.txt to config toolchain

- use hpmicro GNU riscv32 toolchain

Signed-off-by: Zhihong Chen <zhihong.chen@hpmicro.com>

arch/risc-v/src/hpm6750/hpm6750_serial.c

@@ -570,9 +570,9 @@ static void up_detach(struct uart_dev_s *dev)
  *
  * Description:
  *   This is the UART interrupt handler.  It will be invoked when an
- *   interrupt received on the 'irq'  It should call uart_transmitchars or
- *   uart_receivechar to perform the appropriate data transfers.  The
- *   interrupt handling logic must be able to map the 'irq' number into the
+ *   interrupt is received on the 'irq'.  It should call uart_xmitchars or
+ *   uart_recvchars to perform the appropriate data transfers.  The
+ *   interrupt handling logic must be able to map the 'arg' into the
  *   appropriate uart_dev_s structure in order to call these functions.
  *
  ****************************************************************************/

boards/risc-v/hpm6750/hpm6750evk2/README.txt

@@ -15,8 +15,20 @@
   $ cd nuttx
   $ make distclean
   $ ./tools/configure.sh hpm6750evk2:nsh
+  $ make menuconfig
   $ make V=1
 
+  Note: make menuconfig to config toolchain
+  ==================
+    To switch GNU riscv64 toolchain to GNU riscv32 toolchain, the following option must be selected:
+
+    System Type  --->
+        Toolchain Selection   --->
+            [ ] Generic GNU RV64 toolchain
+            [x] Generic GNU RV32 toolchain
+
+    Make sure HPMicro GNU riscv32 toolchain have been installed and be found in PATH.
+
 4. Debug the nuttx with openocd and run
 
   $ picocom -b 115200 /dev/ttyACM0
@@ -24,7 +36,7 @@
   When using fireDAP, command as follows. Those cfg files in the path: sdk_env/hpm_sdk/boards/openocd.
   $ openocd -f probes/cmsis_dap.cfg -f soc/hpm6750-single-core.cfg -f boards/hpm6750evk2.cfg
 
-  $ riscv64-unknown-elf-gdb ./nuttx
+  $ riscv32-unknown-elf-gdb ./nuttx
   (gdb) target extended-remote [ip_addr]:3333
   (gdb) load
   (gdb) c