diff --git a/cpu/stm32f1/lpm_arch.c b/cpu/stm32f1/lpm_arch.c
index c463d6c3c2..e41810c880 100644
--- a/cpu/stm32f1/lpm_arch.c
+++ b/cpu/stm32f1/lpm_arch.c
@@ -29,6 +29,7 @@ void lpm_arch_init(void)
 
 enum lpm_mode lpm_arch_set(enum lpm_mode target)
 {
+    (void) target;
     /* TODO */
     return 0;
 }
diff --git a/cpu/stm32f1/periph/gpio.c b/cpu/stm32f1/periph/gpio.c
index b4a916e905..a3bad7f23d 100644
--- a/cpu/stm32f1/periph/gpio.c
+++ b/cpu/stm32f1/periph/gpio.c
@@ -212,7 +212,7 @@ void gpio_write(gpio_t pin, int value)
 
 void isr_exti(void)
 {
-    for (int i = 0; i < GPIO_ISR_CHAN_NUMOF; i++) {
+    for (unsigned i = 0; i < GPIO_ISR_CHAN_NUMOF; i++) {
         if (EXTI->PR & (1 << i)) {
             EXTI->PR = (1 << i);        /* clear by writing a 1 */
             exti_ctx[i].cb(exti_ctx[i].arg);
diff --git a/cpu/stm32f1/periph/spi.c b/cpu/stm32f1/periph/spi.c
index f33d24e4c3..19bab4dba6 100644
--- a/cpu/stm32f1/periph/spi.c
+++ b/cpu/stm32f1/periph/spi.c
@@ -119,6 +119,9 @@ int spi_init_master(spi_t dev, spi_conf_t conf, spi_speed_t speed)
 
 int spi_init_slave(spi_t dev, spi_conf_t conf, char (*cb)(char))
 {
+    (void) dev;
+    (void) conf;
+    (void) cb;
     /* TODO */
     return -1;
 }
@@ -236,6 +239,8 @@ int spi_transfer_byte(spi_t dev, char out, char *in)
 
 void spi_transmission_begin(spi_t dev, char reset_val)
 {
+    (void) dev;
+    (void) reset_val;
     /* slave mode not implemented, yet */
 }
 
diff --git a/cpu/stm32f4/periph/gpio.c b/cpu/stm32f4/periph/gpio.c
index 50f8124b36..643f4ba34c 100644
--- a/cpu/stm32f4/periph/gpio.c
+++ b/cpu/stm32f4/periph/gpio.c
@@ -208,7 +208,7 @@ void gpio_write(gpio_t pin, int value)
 
 void isr_exti(void)
 {
-    for (int i = 0; i < GPIO_ISR_CHAN_NUMOF; i++) {
+    for (unsigned i = 0; i < GPIO_ISR_CHAN_NUMOF; i++) {
         if (EXTI->PR & (1 << i)) {
             EXTI->PR |= (1 << i);               /* clear by writing a 1 */
             exti_chan[i].cb(exti_chan[i].arg);