diff --git a/boards/common/saml1x/include/periph_conf.h b/boards/common/saml1x/include/periph_conf.h
index c20050122b..17a373781c 100644
--- a/boards/common/saml1x/include/periph_conf.h
+++ b/boards/common/saml1x/include/periph_conf.h
@@ -94,6 +94,8 @@ static const uart_conf_t uart_config[] = {
         .gclk_src = SAM0_GCLK_MAIN,
     },
     {    /* EXT1 */
+        /* For SAML11, see boards/saml11/doc.txt
+         * to properly enable this SERCOM */
         .dev      = &SERCOM1->USART,
         .rx_pin   = GPIO_PIN(PA, 9),
         .tx_pin   = GPIO_PIN(PA, 8),
diff --git a/boards/saml11-xpro/doc.txt b/boards/saml11-xpro/doc.txt
index 2c64efc106..c73e1bc20b 100644
--- a/boards/saml11-xpro/doc.txt
+++ b/boards/saml11-xpro/doc.txt
@@ -68,6 +68,17 @@ Connect the device to your Micro-USB cable.
 
 The standard method for flashing RIOT to the saml11-xpro is using EDBG.
 
+## Special case
+
+SERCOM1 (available on EXT1 connector) needs an extra step to be usable.
+By default, this SERCOM is only available in the secure world. As RIOT
+doesn't support it for now, the only option, to use it, is to enable
+SERCOM non-secure mode. To do so, a fuse bit must be set in User ROW
+flash memory. Such action can be done with the following EDBG command:
+'edbg -t saml11 -F w0,194,1'
+or pass it as argument when calling make:
+EDBG_ARGS="-F w0,194,1" BOARD=saml11-xpro make flash term -C tests/periph_uart
+
 ## Supported Toolchains
 
 For using the saml11-xpro board we strongly recommend the usage of the