diff --git a/drivers/gpio.c b/drivers/gpio.c
index be603b4..5ef4cd1 100644
--- a/drivers/gpio.c
+++ b/drivers/gpio.c
@@ -48,7 +48,7 @@ void gpio_configure(enum GpioPort port, enum GpioPin pin_mask,
 		}
 	}
 	regs->PORTS[port].CRL.word &= ~(0xF * mask);
-	regs->PORTS[port].CRL.word |= (config << 2) | (mode << 0) * mask;
+	regs->PORTS[port].CRL.word |= ((config << 2) | (mode << 0)) * mask;
 
 	//clear config for selected port, then apply new config, 8 last pins
 	mask = 0;
@@ -61,7 +61,7 @@ void gpio_configure(enum GpioPort port, enum GpioPin pin_mask,
 		}
 	}
 	regs->PORTS[port].CRH.word &= ~(0xF * mask);
-	regs->PORTS[port].CRH.word |= (config << 2) | (mode << 0) * mask;
+	regs->PORTS[port].CRH.word |= ((config << 2) | (mode << 0)) * mask;
 }
 
 void gpio_reset(enum GpioPort port, enum GpioPin pin_mask)
@@ -85,3 +85,4 @@ bool gpio_read(enum GpioPort port, enum GpioPin pin_mask)
 
 
 //--local functions-------------------------------------------------------------
+
diff --git a/drivers/gpio.h b/drivers/gpio.h
index 9e5c2a5..7a12484 100644
--- a/drivers/gpio.h
+++ b/drivers/gpio.h
@@ -55,8 +55,9 @@ enum GpioPin {
 };
 
 /**
- * Available modes for a pin. To have a pin in both modes simultaneously, see
- * push-pull configuration in input mode
+ * Available modes for a pin. To have a pin in both modes simultaneously, use
+ * push-pull configuration in input mode but note that the power may be
+ * limited
  */
 enum GpioMode {
 	GPIO_MODE_INPUT = 0,
@@ -66,7 +67,7 @@ enum GpioMode {
 };
 
 /**
- * Available configurations for a pin. Some configurations onlly apply in input
+ * Available configurations for a pin. Some configurations only apply in input
  * mode (denoted "IN") while others only apply in output mode (denoted "OUT")
  */
 enum GpioConfig {
@@ -115,3 +116,4 @@ bool gpio_read(enum GpioPort port, enum GpioPin pin_mask);
 
 
 #endif //_RCC_H_
+