diff --git a/cpu/samd21/periph/adc.c b/cpu/samd21/periph/adc.c
index 779d152d24fa..788cd245e32b 100644
--- a/cpu/samd21/periph/adc.c
+++ b/cpu/samd21/periph/adc.c
@@ -212,9 +212,6 @@ int adc_configure_with_resolution(Adc* adc, uint32_t precision)
     /* Set Voltage Reference */
     adc->REFCTRL.reg = (ADC_0_REF_COM_EN << ADC_REFCTRL_REFCOMP_Pos) | ADC_0_REF_DEFAULT;
 
-    int test = adc->REFCTRL.reg;
-    printf("\nREFCTRL %i\n", test);
-
     switch (precision)
     {
     case ADC_0_RES_8BIT:
diff --git a/tests/plant_node/README.md b/tests/plant_node/README.md
index d478e63c9296..80f2685c8dca 100644
--- a/tests/plant_node/README.md
+++ b/tests/plant_node/README.md
@@ -15,4 +15,12 @@ This test uses timers. Be aware that RIOT timers in the current master may crach
 
 You need to change the standard output device from `UART_0` to `UART_1` to free the external ADC reference voltage pin. Then you need to connect an external tty/USB converter to see outputs on your terminal (i.e.  pyterm). 
 
-When using the samr21-xpro you need the ADC mode with external reference pin. When this is enabled in the periph.conf.h you need to connect the 3V3 pin with the V_ref pin (on samr21-xpro PA04).
\ No newline at end of file
+When using the samr21-xpro you need the ADC mode with external reference pin. When this is enabled in the periph.conf.h you need to connect the 3V3 pin with the V_ref pin (on samr21-xpro PA04).
+
+# Needed pins summary
+
+- GPIO Power pin - GPIO_0 - PA13
+- ADC input pin  - ADC_0_POS_INPUT - PA06
+- ADC ref. pin - ADC_0_REF_DEFAULT - PA04
+- Serial out - UART_1_TX_PIN - PA22
+- Serial int - UART_1_RX_PIN - PA23
\ No newline at end of file
diff --git a/tests/plant_node/main.c b/tests/plant_node/main.c
index ce3d2798d1fe..d42fe4258c9f 100644
--- a/tests/plant_node/main.c
+++ b/tests/plant_node/main.c
@@ -43,7 +43,7 @@ int main(void)
     puts("\nRIOT test for a moisture sensor\n");
 
     timex_t sleep1 = timex_set(1, 0); /* 1 sec. */
-    timex_t sleep2 = timex_set(1, 0); /* 10 sec. */
+    timex_t sleep2 = timex_set(1, 0); /* 1 sec. */
 
     /* initialize a GPIO that powers the sensor just during a measure */
     printf("Initializing GPIO_%i as power supplying pin", GPIO_POWER_PIN);
@@ -91,7 +91,7 @@ int main(void)
             puts("Soil is dry");
         }
 
-             /* wait for next measure */
+         /* wait for next measure */
         vtimer_sleep(sleep2);
     }