diff --git a/examples/pcf8591/main.c b/examples/pcf8591/main.c
index a4dc8a3..442d3c1 100644
--- a/examples/pcf8591/main.c
+++ b/examples/pcf8591/main.c
@@ -23,7 +23,7 @@ static void measure(void *pvParameters)
     while (1)
     {
         vTaskDelay(1000 / portTICK_PERIOD_MS);
-        printf("Value: %d\n", pcf8591_read(&dev, 0x03));
+        printf("Value: %d\n", pcf8591_read(&dev, PCF8591_IC_4_SINGLES, 3));
     }
 }
 
diff --git a/extras/pcf8591/pcf8591.c b/extras/pcf8591/pcf8591.c
index ba06a5e..f1cec30 100644
--- a/extras/pcf8591/pcf8591.c
+++ b/extras/pcf8591/pcf8591.c
@@ -1,20 +1,41 @@
-#include <stddef.h>
-#include <stdint.h>
-
+/**
+ * Driver for 8-bit analog-to-digital conversion and
+ * an 8-bit digital-to-analog conversion PCF8591
+ *
+ * Part of esp-open-rtos
+ * Copyright (C) 2017 Pham Ngoc Thanh <pnt239@gmail.com>
+ *               2017 Ruslan V. Uss <unclerus@gmail.com>
+ * BSD Licensed as described in the file LICENSE
+ */
 #include "pcf8591.h"
 
-/**
- * CAUTION: PLEASE SET LOW FREQUENCY
- */
+#include <stddef.h>
 
-#define PCF8591_CTRL_REG_READ 0x03
+#define BV(x) (1 << (x))
 
-uint8_t pcf8591_read(i2c_dev_t* dev, uint8_t analog_pin)
+#define CTRL_AD_CH_MASK 0x03
+
+#define CTRL_AD_IN_PRG 4
+#define CTRL_AD_IN_PRG_MASK (0x03 << CTRL_AD_IN_PRG)
+
+#define CTRL_DA_OUT_EN 6
+
+uint8_t pcf8591_read(i2c_dev_t *dev, pcf8591_input_conf_t conf, uint8_t channel)
 {
     uint8_t res = 0;
-    uint8_t control_reg = PCF8591_CTRL_REG_READ & analog_pin;
+    uint8_t control_reg =
+            ((conf << CTRL_AD_IN_PRG) & CTRL_AD_IN_PRG_MASK) |
+            (channel & CTRL_AD_CH_MASK) |
+            BV(CTRL_DA_OUT_EN);
 
     i2c_slave_read(dev->bus, dev->addr, &control_reg, &res, 1);
 
     return res;
 }
+
+void pcf8591_write(i2c_dev_t *dev, uint8_t value)
+{
+    uint8_t buf[2] = { BV(CTRL_DA_OUT_EN), value };
+
+    i2c_slave_write(dev->bus, dev->addr, NULL, buf, 2);
+}
diff --git a/extras/pcf8591/pcf8591.h b/extras/pcf8591/pcf8591.h
index 5327323..f136a46 100644
--- a/extras/pcf8591/pcf8591.h
+++ b/extras/pcf8591/pcf8591.h
@@ -1,14 +1,16 @@
 /**
- * Driver for  8-bit analog-to-digital conversion and
+ * Driver for 8-bit analog-to-digital conversion and
  * an 8-bit digital-to-analog conversion PCF8591
  *
  * Part of esp-open-rtos
  * Copyright (C) 2017 Pham Ngoc Thanh <pnt239@gmail.com>
+ *               2017 Ruslan V. Uss <unclerus@gmail.com>
  * BSD Licensed as described in the file LICENSE
  */
 #ifndef _EXTRAS_PCF8591_H_
 #define _EXTRAS_PCF8591_H_
 
+#include <stdint.h>
 #include <i2c/i2c.h>
 
 #ifdef __cplusplus
@@ -16,25 +18,33 @@ extern "C"
 {
 #endif
 
-/**
- * CAUTION: PLEASE SET I2C_FREQUENCY_400K IS 'false' IN 'i2c.h' FILE
- */
-
 #define PCF8591_DEFAULT_ADDRESS 0x48
 
-void pcf8591_init(void); //FIXME : library incomplete ?
+/**
+ * Analog inputs configuration, see datasheet
+ */
+typedef enum {
+    PCF8591_IC_4_SINGLES = 0,   //!< Four single-ended inputs
+    PCF8591_IC_DIFF,            //!< Three differential inputs
+    PCF8591_IC_2_SINGLES_DIFF,  //!< Two single-ended and differnetial mixed
+    PCF8591_IC_2_DIFFS          //!< Two differential inputs
+} pcf8591_input_conf_t;
 
 /**
  * Read input value of an analog pin.
- * @param[in] addr Pointer to device
- * @param[in] analog_pin pin number:
- *            0 - AIN0
- *            1 - AIN1
- *            2 - AIN2
- *            3 - AIN3
+ * @param[in] dev Pointer to device
+ * @param[in] conf Analog inputs configuration
+ * @param[in] channel Analog channel
  * @return analog value
  */
-uint8_t pcf8591_read(i2c_dev_t* dev, uint8_t analog_pin);
+uint8_t pcf8591_read(i2c_dev_t *dev, pcf8591_input_conf_t conf, uint8_t channel);
+
+/**
+ * Write value to analog output
+ * @param[in] dev Pointer to device
+ * @param[in] value DAC value
+ */
+void pcf8591_write(i2c_dev_t *dev, uint8_t value);
 
 
 #ifdef __cplusplus