diff --git a/epaper.c b/epaper.c
index 6ac27b8..86d6385 100644
--- a/epaper.c
+++ b/epaper.c
@@ -39,6 +39,7 @@ int main()
 {
 	uint16_t i;
 	uint16_t j;
+	absolute_time_t t;
 
 	stdio_init_all();
 
@@ -103,20 +104,29 @@ int main()
 	epd_font_set(&epd0, epd_font_inr21_mf);
 	epd_draw_str(&epd0, 250, 154, "Sigma-wrapped text.");
 	epd_update(&epd0);
+	sleep_ms(2000);
 
-	for(;;)
+	t = make_timeout_time_ms(180000); /* full screen refresh every 180 s */
+	for (;;)
 	{
 		uint32_t x;
 		uint32_t y;
 
 		x  = get_rand_32() % EPD_4P2MONO_WIDTH;
-		y  = (get_rand_32() % (EPD_4P2MONO_HEIGHT - 42) + 21);
+		y  = (get_rand_32() % (EPD_4P2MONO_HEIGHT - 28) + 23);
 
-		epd_dbuf_clear(&epd0);
+		//epd_dbuf_clear(&epd0);
 		epd_font_set(&epd0, epd_font_inr21_mf);
 		epd_draw_str(&epd0, x, y, "Sigma-wrapped text.");
-		epd_update(&epd0);
-		sleep_ms(1000);
+		//epd_update(&epd0);
+		/* FIXME: should accept width in pixels and convert to bytes internally */
+		epd_update_partial(&epd0, x % 100, x, y < 23 ? 0 : y - 23, y + 5);
+		//sleep_ms(1000);
+		if(absolute_time_diff_us(t, get_absolute_time()) > 0)
+		{
+			epd_update(&epd0);
+			t = make_timeout_time_ms(180000);
+		}
 	}
 
 	return 0;
diff --git a/epd/epd.c b/epd/epd.c
index 114f240..1cc1082 100644
--- a/epd/epd.c
+++ b/epd/epd.c
@@ -190,3 +190,33 @@ int32_t epd_update(epd_t *epd)
 
 	return epd->display.write(epd);
 }
+
+/**
+ * \brief   send the dbuf to the display
+ *
+ * \details Display the contents of the dbuf on the screen within a specified
+ * window. Falls back on a full update if the display does not implement
+ * partial updates.
+ *
+ * \param[in,out] epd  pointer to an epd_t
+ * \param[in] x0 x-coordinate of first pixel in window
+ * \param[in] x1 x-coordinate of last pixel in window
+ * \param[in] y0 y-coordinate of first pixel in window
+ * \param[in] y1 y-coordinate of last pixel in window
+ *
+ * \returns 0 on success
+ */
+int32_t epd_update_partial(epd_t *epd, uint16_t x0, uint16_t x1, uint16_t y0, uint16_t y1)
+{
+	return_val_if_fail(epd, -1);
+	return_val_if_fail(epd->dbuf, -1);
+
+	if(epd->display.write_partial)
+	{
+		return epd->display.write_partial(epd, x0, x1, y0, y1);
+	}
+	else
+	{
+		return epd->display.write(epd);
+	}
+}
diff --git a/epd/epd.h b/epd/epd.h
index 6987776..27c8825 100644
--- a/epd/epd.h
+++ b/epd/epd.h
@@ -35,10 +35,12 @@ typedef struct epd_platform_config_s {
 	void *udata;
 } epd_platform_config_t;
 typedef int32_t (*epd_write_dbuf)(epd_t *);
+typedef int32_t (*epd_write_dbuf_partial)(epd_t *, uint16_t, uint16_t, uint16_t, uint16_t);
 typedef struct epd_display_config_s {
 	uint32_t w;
 	uint32_t h;
 	epd_write_dbuf write;
+	epd_write_dbuf_partial write_partial;
 } epd_display_config_t;
 typedef uint16_t (*epd_char_cb)(epd_t *epd, uint8_t b);
 typedef struct epd_font_decode_s
@@ -87,5 +89,6 @@ int8_t epd_dbuf_set(epd_t *epd, epd_dbuf_t *dbuf);
 int8_t epd_dbuf_clear(epd_t *epd);
 void epd_draw_line(epd_t *epd, uint16_t x, uint16_t y, uint16_t len, epd_dir_t dir);
 int32_t epd_update(epd_t *epd);
+int32_t epd_update_partial(epd_t *epd, uint16_t x0, uint16_t x1, uint16_t y0, uint16_t y1);
 
 #endif /* EPD_H_ */
diff --git a/epd/epd_4p2mono.c b/epd/epd_4p2mono.c
index 7e6d5de..52efb20 100644
--- a/epd/epd_4p2mono.c
+++ b/epd/epd_4p2mono.c
@@ -987,6 +987,7 @@ static const uint8_t testimg[] = {
 
 /* Function Prototypes */
 static int32_t epd_4p2mono_write_dbuf(epd_t *epd);
+static int32_t epd_4p2mono_write_dbuf_partial(epd_t *epd, uint16_t x0, uint16_t x1, uint16_t y0, uint16_t y1);
 
 /* Function Definitions */
 static inline void epd_rst(epd_t *epd)
@@ -1027,9 +1028,10 @@ static inline void busy_wait(epd_t *epd)
 void epd_4p2mono_init(epd_t *epd)
 {
 	epd_display_config_t cfg = {
-		.w     = EPD_4P2MONO_WIDTH,
-		.h     = EPD_4P2MONO_HEIGHT,
-		.write = epd_4p2mono_write_dbuf
+		.w             = EPD_4P2MONO_WIDTH,
+		.h             = EPD_4P2MONO_HEIGHT,
+		.write         = epd_4p2mono_write_dbuf,
+		.write_partial = epd_4p2mono_write_dbuf_partial
 	};
 
 	/* configure the display */
@@ -1140,3 +1142,46 @@ static int32_t epd_4p2mono_write_dbuf(epd_t *epd)
 
 	return 0;
 }
+
+static int32_t epd_4p2mono_write_dbuf_partial(epd_t *epd, uint16_t x0, uint16_t x1, uint16_t y0, uint16_t y1)
+{
+	const uint32_t w = (EPD_4P2MONO_WIDTH % 8) ? (EPD_4P2MONO_WIDTH / 8 + 1) : (EPD_4P2MONO_WIDTH / 8);
+	const uint16_t x0b = x0 / 8;
+	const uint16_t x1b = ((x1 % 8) ? (x1 / 8 + 1) : (x1 / 8)) - 1;
+	uint32_t i;
+	uint32_t j;
+	const uint8_t hrstu = (uint8_t) (x0b >> 5) & 0x01;
+	const uint8_t hrstl = (uint8_t) (x0b << 3);
+	const uint8_t hredu = (uint8_t) (x1b >> 5) & 0x01;
+	const uint8_t hredl = (uint8_t) (x1b << 3);
+	const uint8_t vrstu = (uint8_t) (y0 >> 8) & 0x01;
+	const uint8_t vrstl = (uint8_t) (y0);
+	const uint8_t vredu = (uint8_t) (y1 >> 8) & 0x01;
+	const uint8_t vredl = (uint8_t) (y1);
+
+	cmd_byte(epd, CMD_PTL);
+	data_byte(epd, hrstu); /* HRST[8] */
+	data_byte(epd, hrstl); /* HRST[7:3] */
+	data_byte(epd, hredu); /* HRED[8] */
+	data_byte(epd, hredl); /* HRED7:3] */
+	data_byte(epd, vrstu); /* VRST[8] */
+	data_byte(epd, vrstl); /* VRST[7:0] */
+	data_byte(epd, vredu); /* VRED[8] */
+	data_byte(epd, vredl); /* VRED7:0] */
+	data_byte(epd, 0x00);  /* PT_SCAN */
+	cmd_byte(epd, CMD_PTIN);
+	cmd_byte(epd, CMD_DTM2);
+	for(j = y0; j <= y1; j++)
+	{
+		for(i = x0b; i <= x1b; i++)
+		{
+			data_byte(epd, epd->dbuf[i + (w * j)]);
+		}
+	}
+	cmd_byte(epd, CMD_DRF);
+	busy_wait(epd);
+	cmd_byte(epd, CMD_PTOUT);
+	busy_wait(epd);
+
+	return 0;
+}