diff --git a/firmware/lux.cpp b/firmware/lux.cpp
index 540e71a..8ab3b11 100644
--- a/firmware/lux.cpp
+++ b/firmware/lux.cpp
@@ -20,6 +20,12 @@ extern "C" void signal_led(bool state) {
     gpio_write(signal_led_pin, !state);
 }
 
+void int_to_hex(uint8_t i, char buf[2]) {
+    uint8_t hex_charset[] = "0123456789ABCDEF";
+    buf[0] = hex_charset[i >> 4];
+    buf[1] = hex_charset[i & 0x0F];
+}
+
 extern "C" void lux_task(void *pvParameters) {
 
     gpio_enable(signal_led_pin, GPIO_OUTPUT);
@@ -33,13 +39,21 @@ extern "C" void lux_task(void *pvParameters) {
     uint8_t cnt = 0;
 
     while(1) {
+        uint8_t buf[2];
         spi_transfer_8(1, charset[cnt++]);
         for(volatile int i = 0; i < 100; i++);
-        spi_transfer_8(1, 0x00);
+        spi_read(1, 0x00, buf, 2, 1);
+
+        char hex[5];
+        int_to_hex(buf[0], hex);
+        int_to_hex(buf[1], hex + 2);
+        hex[4] = '\0';
+        printf("lux_task output: %s\n", hex);
 
         vTaskDelay(1000/portTICK_PERIOD_MS);
         cnt %= sizeof(charset);
     }
 
+
     vTaskDelete(nullptr);
 }
\ No newline at end of file