diff --git a/STM32/CM7/Core/Inc/global_state.h b/STM32/CM7/Core/Inc/global_state.h
index fcdcef3..66e70dd 100644
--- a/STM32/CM7/Core/Inc/global_state.h
+++ b/STM32/CM7/Core/Inc/global_state.h
@@ -6,6 +6,7 @@
 #include <stdint.h>
 
 #define MAX_CAM_MISS 2
+#define SPARK_ADVANCE 20
 
 typedef enum { SYNC_OK = 0, SYNC_PENDING = 1, SYNC_NOT_OK = 2 } sync_state_t;
 
diff --git a/STM32/CM7/Core/Inc/ring_buffer.h b/STM32/CM7/Core/Inc/ring_buffer.h
index de92307..a33c228 100644
--- a/STM32/CM7/Core/Inc/ring_buffer.h
+++ b/STM32/CM7/Core/Inc/ring_buffer.h
@@ -8,8 +8,8 @@ typedef struct ring_buffer_t {
   uint8_t w_head;
 } ring_buffer_t;
 
-inline void ringBufferPush(ring_buffer_t *rb, uint32_t value);
+inline void ringBufferPush(volatile ring_buffer_t *rb, uint32_t value);
 
-inline uint32_t ringBufferRead(ring_buffer_t *rb, uint8_t idx);
+inline uint32_t ringBufferRead(volatile ring_buffer_t *rb, uint8_t neg_idx);
 
-inline void ringBufferRevert(ring_buffer_t *rb, uint8_t val);
+inline void ringBufferRevert(volatile ring_buffer_t *rb, uint8_t val);
diff --git a/STM32/CM7/Core/Src/ring_buffer.c b/STM32/CM7/Core/Src/ring_buffer.c
index c5d5a09..f42d79a 100644
--- a/STM32/CM7/Core/Src/ring_buffer.c
+++ b/STM32/CM7/Core/Src/ring_buffer.c
@@ -6,17 +6,17 @@
 #include <ring_buffer.h>
 #include <stdbool.h>
 
-void ringBufferPush(ring_buffer_t *rb, uint32_t value) {
+void ringBufferPush(volatile ring_buffer_t *rb, uint32_t value) {
   rb->buffer[rb->w_head] = value;
   rb->w_head++;
   return;
 }
 
-uint32_t ringBufferRead(ring_buffer_t *rb, uint8_t idx) {
-  return rb->buffer[rb->w_head - 1 - idx];
+uint32_t ringBufferRead(volatile ring_buffer_t *rb, uint8_t neg_idx) {
+  return rb->buffer[rb->w_head - 1 - neg_idx];
 }
 
-void ringBufferRevert(ring_buffer_t *rb, uint8_t val) {
+void ringBufferRevert(volatile ring_buffer_t *rb, uint8_t val) {
   rb->w_head -= val;
   return;
 }
diff --git a/STM32/CM7/Core/Src/tasks/crank.c b/STM32/CM7/Core/Src/tasks/crank.c
index 6e14295..36345b8 100644
--- a/STM32/CM7/Core/Src/tasks/crank.c
+++ b/STM32/CM7/Core/Src/tasks/crank.c
@@ -8,6 +8,7 @@
 #include "main.h"
 #include "ring_buffer.h"
 #include "tasks.h"
+#include <stdint.h>
 
 void crankHandler(void *argument) {
   for (;;) {
@@ -59,6 +60,13 @@ void crankHandler(void *argument) {
     if (state_g.crank_state == CYCLE_COMPRESSION &&
         state_g.sync_state == SYNC_OK) {
       DEBUG_LOG("Spark schedule reached, congrats\n\r");
+      uint32_t t_now = ringBufferRead(&state_g.crank_RB, 0);
+      uint32_t t_prev = ringBufferRead(&state_g.crank_RB, 1);
+
+      uint32_t d1a = t_now - t_prev;
+      // TODO: Map interpolation rather than SPARK_ADVANCE CONSTANT
+      uint32_t d_spark = d1a * (45 - SPARK_ADVANCE) / 180;
+      uint32_t t_spark = t_now + d_spark;
       // TODO: schedule spark
     }
   }