diff --git a/klippy/pins.py b/klippy/pins.py
index 20f78295..9a3f1ccf 100644
--- a/klippy/pins.py
+++ b/klippy/pins.py
@@ -40,6 +40,7 @@ MCU_PINS = {
     "at90usb1286": port_pins(6), "at90usb646": port_pins(6),
     "atmega1280": port_pins(12), "atmega2560": port_pins(12),
     "sam3x8e": port_pins(4, 32),
+    "samd21g": port_pins(2, 32),
     "stm32f103": port_pins(5, 16),
     "lpc176x": lpc_pins(),
     "pru": beaglebone_pins(),
diff --git a/src/samd21/Kconfig b/src/samd21/Kconfig
index afdd3dc0..d8108f71 100644
--- a/src/samd21/Kconfig
+++ b/src/samd21/Kconfig
@@ -5,6 +5,7 @@ if MACH_SAMD21
 config SAMD_SELECT
     bool
     default y
+    select HAVE_GPIO
 
 config BOARD_DIRECTORY
     string
diff --git a/src/samd21/gpio.c b/src/samd21/gpio.c
index 3ae51f74..cf2d6618 100644
--- a/src/samd21/gpio.c
+++ b/src/samd21/gpio.c
@@ -4,8 +4,17 @@
 //
 // This file may be distributed under the terms of the GNU GPLv3 license.
 
+#include "board/irq.h" // irq_save
+#include "command.h" // shutdown
+#include "gpio.h" // gpio_out_setup
 #include "internal.h" // gpio_peripheral
 #include "samd21.h" // PORT
+#include "sched.h" // sched_shutdown
+
+
+/****************************************************************
+ * Pin multiplexing
+ ****************************************************************/
 
 void
 gpio_peripheral(char bank, uint32_t bit, char ptype, uint32_t pull_up)
@@ -20,3 +29,81 @@ gpio_peripheral(char bank, uint32_t bit, char ptype, uint32_t pull_up)
     pg->PINCFG[bit].reg = ((ptype ? PORT_PINCFG_PMUXEN : 0)
                            | (pull_up ? PORT_PINCFG_PULLEN : 0));
 }
+
+
+/****************************************************************
+ * General Purpose Input Output (GPIO) pins
+ ****************************************************************/
+
+#define GPIO(PORT, NUM) (((PORT)-'A') * 32 + (NUM))
+#define GPIO2PORT(PIN) ((PIN) / 32)
+#define GPIO2NUM(PIN) ((PIN) % 32)
+#define GPIO2BIT(PIN) (1<<((PIN) % 32))
+#define NUM_PORT 2
+
+struct gpio_out
+gpio_out_setup(uint8_t pin, uint8_t val)
+{
+    if (GPIO2PORT(pin) >= NUM_PORT)
+        goto fail;
+    PortGroup *pg = &PORT->Group[GPIO2PORT(pin)];
+    uint32_t bit = GPIO2BIT(pin);
+    irqstatus_t flag = irq_save();
+    if (val)
+        pg->OUTSET.reg = bit;
+    else
+        pg->OUTCLR.reg = bit;
+    pg->DIRSET.reg = bit;
+    pg->PINCFG[GPIO2NUM(pin)].reg = 0;
+    irq_restore(flag);
+    return (struct gpio_out){ .regs=pg, .bit=bit };
+fail:
+    shutdown("Not an output pin");
+}
+
+void
+gpio_out_toggle_noirq(struct gpio_out g)
+{
+    PortGroup *pg = g.regs;
+    pg->OUTTGL.reg = g.bit;
+}
+
+void
+gpio_out_toggle(struct gpio_out g)
+{
+    gpio_out_toggle_noirq(g);
+}
+
+void
+gpio_out_write(struct gpio_out g, uint8_t val)
+{
+    PortGroup *pg = g.regs;
+    if (val)
+        pg->OUTSET.reg = g.bit;
+    else
+        pg->OUTCLR.reg = g.bit;
+}
+
+
+struct gpio_in
+gpio_in_setup(uint8_t pin, int8_t pull_up)
+{
+    if (GPIO2PORT(pin) >= NUM_PORT)
+        goto fail;
+    PortGroup *pg = &PORT->Group[GPIO2PORT(pin)];
+    uint32_t bit = GPIO2BIT(pin);
+    irqstatus_t flag = irq_save();
+    pg->PINCFG[GPIO2NUM(pin)].reg = pull_up > 0 ? PORT_PINCFG_PULLEN : 0;
+    pg->DIRCLR.reg = bit;
+    irq_restore(flag);
+    return (struct gpio_in){ .regs=pg, .bit=bit };
+fail:
+    shutdown("Not an input pin");
+}
+
+uint8_t
+gpio_in_read(struct gpio_in g)
+{
+    PortGroup *pg = g.regs;
+    return !!(pg->IN.reg & g.bit);
+}
diff --git a/src/samd21/gpio.h b/src/samd21/gpio.h
new file mode 100644
index 00000000..0cba5dba
--- /dev/null
+++ b/src/samd21/gpio.h
@@ -0,0 +1,22 @@
+#ifndef __SAM3X8E_GPIO_H
+#define __SAM3X8E_GPIO_H
+
+#include <stdint.h>
+
+struct gpio_out {
+    void *regs;
+    uint32_t bit;
+};
+struct gpio_out gpio_out_setup(uint8_t pin, uint8_t val);
+void gpio_out_toggle_noirq(struct gpio_out g);
+void gpio_out_toggle(struct gpio_out g);
+void gpio_out_write(struct gpio_out g, uint8_t val);
+
+struct gpio_in {
+    void *regs;
+    uint32_t bit;
+};
+struct gpio_in gpio_in_setup(uint8_t pin, int8_t pull_up);
+uint8_t gpio_in_read(struct gpio_in g);
+
+#endif // gpio.h