boards: st: nucleo_n657x0_q: clarify boot pins information

Clarify the BOOT0/BOOT1 configuration needed to program the flash
memory or to load the image straight in RAM (serial boot variant 'sb').

Fix the build directive when 'sb' variant is to be used.

Explicit what the 2 USB connectors are used for in the 'sb' variant
configuration.

Signed-off-by: Etienne Carriere <[email protected]>

Author: etienne-lms

boards/st/nucleo_n657x0_q/doc/index.rst

@@ -176,7 +176,7 @@ To program the board, there are two options:
   and executed from there.
 - Optionally, it can also be taken advantage from the serial boot interface provided
   by the boot ROM. In that case, firmware is directly loaded in RAM and executed from
-  there. It is not retained.
+  there. It is not retained in persistent memory.
 
 Programming an application to NUCLEO-N657X0-Q
 ---------------------------------------------
@@ -199,33 +199,38 @@ First, connect the NUCLEO-N657X0-Q to your host computer using the ST-Link USB p
          .. note::
             For flashing, before powering the board, set the boot pins in the following configuration:
 
-            * BOOT0: 0
-            * BOOT1: 1
+            * BOOT0: 0 (jumper JP1 in position 1, printed on PCB)
+            * BOOT1: 1 (jumper JP2 in position 2, not-printed on PCB)
 
             After flashing, to run the application, set the boot pins in the following configuration:
 
-            * BOOT1: 0
+            * BOOT0: 0 (jumper JP1 in position 1, printed on PCB)
+            * BOOT1: 0 (jumper JP2 in position 1, printed on PCB)
 
-	    Power off and on the board again.
+            Power off and on the board again.
 
       .. group-tab:: Serial Boot Loader (USB)
 
-         Additionally, connect the NUCLEO-N657X0-Q to your host computer using the USB port.
-         In this configuration, ST-Link is used to power the board and for serial communication
-         over the Virtual COM Port.
+         Additionally to the USB/ST-Link, connect the NUCLEO-N657X0-Q to your
+         host computer using the USB port (USB/CN8).
+
+         In this configuration, ST-Link (USB connector CN10) is used to power
+         the board and for serial communication over the Virtual COM Port,
+         while USB/CN8 is used to send the Zephyr image to Boot ROM for loading
+         it in RAM and executing it.
 
          .. note::
             Before powering the board, set the boot pins in the following configuration:
 
-            * BOOT0: 1
-            * BOOT1: 0
+            * BOOT0: 1 (jumper JP1 in position 2, not-printed on PCB)
+            * BOOT1: 0 (jumper JP2 in position 1, printed on PCB)
 
          Build and load an application using ``nucleo_n657x0_q/stm32n657xx/sb`` target (you
          can also use the shortened form: ``nucleo_n657x0_q//sb``)
 
          .. zephyr-app-commands::
             :zephyr-app: samples/hello_world
-            :board: nucleo_n657x0_q
+            :board: nucleo_n657x0_q//sb
             :goals: build flash