diff --git a/artiq/firmware/libboard_artiq/wrpll.rs b/artiq/firmware/libboard_artiq/wrpll.rs
index 826a643aa..22072f403 100644
--- a/artiq/firmware/libboard_artiq/wrpll.rs
+++ b/artiq/firmware/libboard_artiq/wrpll.rs
@@ -9,7 +9,7 @@ mod i2c {
         Helper
     }
 
-    fn half_period() { clock::spin_us(10) }
+    fn half_period() { clock::spin_us(1) }
     const SDA_MASK: u8 = 2;
     const SCL_MASK: u8 = 1;