diff --git a/part10-multicore/io.c b/part10-multicore/io.c
index a2a888d..b9ba71f 100644
--- a/part10-multicore/io.c
+++ b/part10-multicore/io.c
@@ -19,8 +19,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part11-breakout-smp/lib/io.c b/part11-breakout-smp/lib/io.c
index 34a02aa..77e23eb 100644
--- a/part11-breakout-smp/lib/io.c
+++ b/part11-breakout-smp/lib/io.c
@@ -19,8 +19,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part12-wgt/lib/io.c b/part12-wgt/lib/io.c
index 34a02aa..77e23eb 100644
--- a/part12-wgt/lib/io.c
+++ b/part12-wgt/lib/io.c
@@ -19,8 +19,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part13-interrupts/lib/io.c b/part13-interrupts/lib/io.c
index 34a02aa..77e23eb 100644
--- a/part13-interrupts/lib/io.c
+++ b/part13-interrupts/lib/io.c
@@ -19,8 +19,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part14-spi-ethernet/lib/io.c b/part14-spi-ethernet/lib/io.c
index 34a02aa..77e23eb 100644
--- a/part14-spi-ethernet/lib/io.c
+++ b/part14-spi-ethernet/lib/io.c
@@ -19,8 +19,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part4-miniuart/io.c b/part4-miniuart/io.c
index 9561780..d7b2985 100644
--- a/part4-miniuart/io.c
+++ b/part4-miniuart/io.c
@@ -17,8 +17,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part5-framebuffer/io.c b/part5-framebuffer/io.c
index e8af328..b58f996 100644
--- a/part5-framebuffer/io.c
+++ b/part5-framebuffer/io.c
@@ -18,8 +18,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part6-breakout/io.c b/part6-breakout/io.c
index e06b64d..c5134ab 100644
--- a/part6-breakout/io.c
+++ b/part6-breakout/io.c
@@ -18,8 +18,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part7-bluetooth/io.c b/part7-bluetooth/io.c
index 8a591b7..33b3962 100644
--- a/part7-bluetooth/io.c
+++ b/part7-bluetooth/io.c
@@ -18,8 +18,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part8-breakout-ble/io.c b/part8-breakout-ble/io.c
index 8a591b7..33b3962 100644
--- a/part8-breakout-ble/io.c
+++ b/part8-breakout-ble/io.c
@@ -18,8 +18,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }
diff --git a/part9-sound/io.c b/part9-sound/io.c
index a2a888d..b9ba71f 100644
--- a/part9-sound/io.c
+++ b/part9-sound/io.c
@@ -19,8 +19,8 @@ enum {
 
 enum {
     Pull_None = 0,
-    Pull_Down = 1, // Are down and up the right way around?
-    Pull_Up = 2
+    Pull_Down = 2,
+    Pull_Up = 1
 };
 
 void mmio_write(long reg, unsigned int val) { *(volatile unsigned int *)reg = val; }