diff --git a/api/node.proto b/api/node.proto
index 4495315..4991659 100644
--- a/api/node.proto
+++ b/api/node.proto
@@ -57,6 +57,7 @@ message NodeStatus {
     StreamInStatus stream_in = 5;
     ElectricalStimulationStatus electrical_stimulation = 6;
     ApplicationNodeStatus application = 7;
+    OpticalStimulationStatus optical_stimulation = 8;
   }
 }
 
diff --git a/api/nodes/optical_stimulation.proto b/api/nodes/optical_stimulation.proto
index 081a80d..dcbfa6a 100644
--- a/api/nodes/optical_stimulation.proto
+++ b/api/nodes/optical_stimulation.proto
@@ -33,3 +33,8 @@ message OpticalStimFrame {
   // For active, this represents frame on time
   uint64 duration_us = 7;
 }
+
+message OpticalStimulationStatus {
+  // How many frames have we written?
+  uint64 frames_written = 1;
+}
diff --git a/api/time.proto b/api/time.proto
index 429a07e..b82ecec 100644
--- a/api/time.proto
+++ b/api/time.proto
@@ -46,7 +46,8 @@ enum TimeSource {
     TIME_SOURCE_STEADY_CLOCK = 1;
   
     // Calculate timestamps based on sample counter and sampling rate
-    // timestamp = (sample_counter / sample_rate) + initial_steady_clock_value
+    // counter_diff = (counter - first_counter)
+    // timestamp_ns = (counter_diff * 1e9 / sample_rate) + initial_steady_clock_value
     // Where initial_steady_clock_value = get_steady_clock_now() at start
     TIME_SOURCE_SAMPLE_COUNTER = 2;
 }