diff --git a/st7920.c b/st7920.c
index 955142b..5d295a8 100644
--- a/st7920.c
+++ b/st7920.c
@@ -104,7 +104,10 @@ esp_err_t st7920_init(const st7920_config_t *config, st7920_device_t *device) {
     return ESP_OK;
 }
 
-esp_err_t st7920_clear(st7920_device_t *dev) {
+
+
+esp_err_t st7920_clear(void *p) {
+    st7920_device_t* dev = (st7920_device_t*)p;
     memset(dev->framebuffer, 0, sizeof(dev->framebuffer));
     
     // Clear display RAM
@@ -120,7 +123,8 @@ esp_err_t st7920_set_backlight(const st7920_device_t *dev, const bool backlight)
     return gpio_set_level(dev->pin_bl, backlight);
 }
 
-esp_err_t st7920_update_screen(const st7920_device_t *dev) {
+esp_err_t st7920_update_screen(const void *p) {
+    const st7920_device_t* dev = (st7920_device_t*)p;
     // ST7920 is actually two 128x32 disps, we send row by row to each of them
     for (uint8_t y = 0; y < 64; y++) {
         const bool upper_half = y < 32;
@@ -147,10 +151,12 @@ static void st7920_set_pixel_color(st7920_device_t *dev, const uint8_t x, const
         dev->framebuffer[byte_index] &= ~(1 << bit_index);
 }
 
-void st7920_draw_pixel(void *dev, const uint8_t x, const uint8_t y) {
+esp_err_t st7920_draw_pixel(void *dev, const uint8_t x, const uint8_t y) {
     st7920_set_pixel_color(dev, x, y, 1);
+    return ESP_OK;
 }
 
-void st7920_clear_pixel(void *dev, const uint8_t x, const uint8_t y) {
+esp_err_t st7920_clear_pixel(void *dev, const uint8_t x, const uint8_t y) {
     st7920_set_pixel_color(dev, x, y, 0);
+    return ESP_OK;
 }
\ No newline at end of file