diff --git a/src/App.cpp b/src/App.cpp
index 0320ac9..e4dcc62 100644
--- a/src/App.cpp
+++ b/src/App.cpp
@@ -17,9 +17,12 @@ App::App() {
 
 uint32_t App::main() {
 
-    DemoTask demoTask{};
+    ESP_LOGI(__FILE__, "Running App::main()");
 
-    demoTask.start("BlinkTask", 2048, 5, 1);
+    static DemoTask demoTask{};
+
+    ESP_LOGI(__FILE__, "Starting DemoTask");
+    demoTask.start("DemoTask", 4096, 5, 1);
 
     return 1;
 }
diff --git a/src/DemoTask.cpp b/src/DemoTask.cpp
index 13a1d56..a5bad7b 100644
--- a/src/DemoTask.cpp
+++ b/src/DemoTask.cpp
@@ -15,30 +15,18 @@ DemoTask::DemoTask() {
 
 void DemoTask::run() {
 
-    /*
-    ESP_LOGI(TAG, "Example configured to blink GPIO LED!");
-    gpio_reset_pin(gpio_onboardLed);
-    gpio_set_direction(gpio_onboardLed, GPIO_MODE_OUTPUT);
+    ESP_LOGI(__FILE__, "Demo Task: run()");
 
-    while (1) {
-        ESP_LOGI(TAG, "Turning the LED %s!", ledState == true ? "ON" : "OFF");
-        gpio_set_level(gpio_onboardLed, ledState);
-        ledState = !ledState;
-        vTaskDelay(blinkTime / portTICK_PERIOD_MS);
-    }
-    */
+    ssd_595_t dev = { gpio_ssd_data, gpio_ssd_clk, gpio_ssd_latch, true };
+    SsdInterface ssd(&dev, ssdDigits);
 
-    ESP_LOGI(__FILE__, "Demo Task");
-
-    SsdInterface ssd(gpio_ssd_data, gpio_ssd_clk, gpio_ssd_latch, ssdDigits);
     uint32_t delay = 500; // ms
-    uint8_t byte = 0x00;
+    uint8_t digit = 0;
 
     while(1) {
-        ESP_LOGI(__FILE__, "Shifting out byte %02hhx", byte);
-
-        ssd.writeRaw(&byte, 1);
-        byte++;
+        ssd.writeRaw(&digitMap[digit], 1);
+        digit++;
+        if(digit >= 16) digit = 0;
 
         vTaskDelay(delay / portTICK_PERIOD_MS);
     }
diff --git a/src/SsdInterface.cpp b/src/SsdInterface.cpp
index 5fdd61d..a0522dc 100644
--- a/src/SsdInterface.cpp
+++ b/src/SsdInterface.cpp
@@ -1,11 +1,9 @@
 
 #include "SsdInterface.hpp"
 
-SsdInterface::SsdInterface(const uint8_t dataPin, const uint8_t clockPin, const uint8_t latchPin, size_t numDigits) : numDigits_(numDigits) {
+SsdInterface::SsdInterface(const ssd_595_t* device, size_t numDigits) : device_(device), numDigits_(numDigits) {
 
-    // create device
-    static ssd_595_t dev = { (gpio_num_t)dataPin, (gpio_num_t)clockPin, (gpio_num_t)latchPin };
-    device_ = &dev;
+    shiftInit(device_);
 
 }
 
diff --git a/src/SsdInterface.hpp b/src/SsdInterface.hpp
index 8521a90..9387483 100644
--- a/src/SsdInterface.hpp
+++ b/src/SsdInterface.hpp
@@ -10,7 +10,7 @@ class SsdInterface {
 
 public:
 
-    SsdInterface(const uint8_t dataPin, const uint8_t clockPin, const uint8_t latchPinPin, size_t numDigits);
+    SsdInterface(const ssd_595_t* device, size_t numDigits);
     ~SsdInterface() = default;
 
     // Outputs the data straight to hardware, mostly for testing purposes
@@ -35,7 +35,7 @@ public:
 
 private:
 
-    ssd_595_t* device_;
+    const ssd_595_t* device_;
 
     size_t numDigits_; // number of chained digits
     uint8_t* data_; // pointer to the data written
diff --git a/src/TaskBase.cpp b/src/TaskBase.cpp
index ca6ff53..e1cedca 100644
--- a/src/TaskBase.cpp
+++ b/src/TaskBase.cpp
@@ -1,6 +1,8 @@
 
 #include "TaskBase.hpp"
 
+#include "esp_log.h"
+
 void TaskBase::start(const char* name, uint32_t stackSize, UBaseType_t priority, BaseType_t core) {
     xTaskCreatePinnedToCore(&TaskBase::taskEntryPoint, name, stackSize, this, priority, &handle, core);
     return;
diff --git a/src/drivers/ssd.c b/src/drivers/ssd.c
index 26aa716..525f2fb 100644
--- a/src/drivers/ssd.c
+++ b/src/drivers/ssd.c
@@ -2,6 +2,7 @@
 #include "ssd.h"
 
 #include "esp_rom_sys.h"
+#include "esp_log.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -9,23 +10,28 @@ extern "C" {
 
 inline void pulse(gpio_num_t pin) {
     gpio_set_level(pin, 1);
-    esp_rom_delay_us(1);
     gpio_set_level(pin, 0);
-    esp_rom_delay_us(1);
 }
 
 void shiftInit(const ssd_595_t* device) {
+
+    gpio_reset_pin(device->dataPin);
+    gpio_reset_pin(device->clockPin);
+    gpio_reset_pin(device->latchPin);
+
     gpio_config_t ioConfig = {
         .mode = GPIO_MODE_OUTPUT,
         .pin_bit_mask = (1ULL << device->dataPin)  |
                         (1ULL << device->clockPin) |
-                        (1ULL << device->latchPin)
+                        (1ULL << device->latchPin),
     };
     gpio_config(&ioConfig);
 
     gpio_set_level(device->dataPin, 0);
     gpio_set_level(device->clockPin, 0);
     gpio_set_level(device->latchPin, 0);
+
+    ESP_LOGI(__FILE__, "ssd_595 initialized");
 }
 
 void addDecimal(uint8_t* data) {
@@ -34,8 +40,9 @@ void addDecimal(uint8_t* data) {
 }
 
 void shiftByte(const ssd_595_t* device, uint8_t byte) {
-    for(int i = 0; i < __CHAR_BIT__; i++) {
-        gpio_set_level(device->dataPin, (byte >> i) & 0x1);
+    for(int i = 0; i < __CHAR_BIT__ ; i++) {
+        uint32_t level = ((byte >> i) & 0x1) ^ device->commonCathode;
+        gpio_set_level(device->dataPin, level);
         pulse(device->clockPin);
     }
     pulse(device->latchPin);
diff --git a/src/drivers/ssd.h b/src/drivers/ssd.h
index da79d27..17cdebd 100644
--- a/src/drivers/ssd.h
+++ b/src/drivers/ssd.h
@@ -14,6 +14,7 @@ typedef struct {
     gpio_num_t dataPin;
     gpio_num_t clockPin;
     gpio_num_t latchPin;
+    bool commonCathode; // false = common anode
 } ssd_595_t;
 
 // encoding of digits on the seven segment display