Add information on compatibility issue between JTAG and AT firmware.

docs/en/api-guides/jtag-debugging/index.rst

@@ -287,6 +287,7 @@ This section provides collection of links to all tips and quirks referred to fro
 * :ref:`jtag-debugging-tip-openocd-configure-target`
 * :ref:`jtag-debugging-tip-reset-by-debugger`
 * :ref:`jtag-debugging-tip-jtag-pins-reconfigured`
+* :ref:`jtag-debugging-tip-at-firmware-issue`
 * :ref:`jtag-debugging-tip-reporting-issues`
 
 

docs/en/api-guides/jtag-debugging/tips-and-quirks.rst

@@ -235,6 +235,16 @@ Below is an excerpt from series of errors reported by GDB after the application
     cpu1: xtensa_resume (line 431): DSR (FFFFFFFF) indicates DIR instruction generated an overrun!
 
 
+.. _jtag-debugging-tip-at-firmware-issue:
+
+JTAG and ESP32-WROOM-32 AT firmware Compatibility Issue
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The ESP32-WROOM series of modules come pre-flashed with AT firmware. This firmware configures the pins GPIO12 to GPIO15 as SPI slave interface, which makes using JTAG impossible.
+
+To make JTAG available, build new firmware that is not using pins GPIO12 to GPIO15 dedicated to JTAG communication. After that, flash the firmware onto your module. See also :ref:`jtag-debugging-tip-jtag-pins-reconfigured`.
+
+
 .. _jtag-debugging-tip-reporting-issues:
 
 Reporting issues with OpenOCD / GDB