diff --git a/.github/ci/build.sh b/.github/ci/build.sh
index bdf7490..d9e1478 100755
--- a/.github/ci/build.sh
+++ b/.github/ci/build.sh
@@ -13,4 +13,32 @@ hashtime save /ci/cache/filetime.json
 
 cargo fmt -- --check
 
+# clone stm32-data-generated at the merge base
+# so the diff will show this PR's effect
+git clone --depth 1 --branch stm32-data-$(git merge-base HEAD main) https://github.com/embassy-rs/stm32-data-generated/ build
+
 ./d ci
+
+# upload diff
+(
+    cd build
+    git diff --color data | aha --black > /ci/artifacts/diff.html
+)
+
+# upload generated data to a fake git repo at
+# https://ci.embassy.dev/jobs/$ID/artifacts/generated.git
+# this allows testing the corresponding embassy-stm32 PR before merging the stm32-data one.
+(
+    cd build
+    rm -rf .git
+    git init
+    git add .
+    git commit -m 'generated'
+    git gc  # makes cloning faster
+    git update-server-info  # generate .git/info/refs
+    mv .git /ci/artifacts/generated.git
+)
+
+cat > /ci/comment.md <<EOF
+diff: https://ci.embassy.dev/jobs/$(jq -r .id < /ci/job.json)/artifacts/diff.html
+EOF
diff --git a/.github/ci/generated.sh b/.github/ci/generated.sh
index 098244e..9bc6257 100755
--- a/.github/ci/generated.sh
+++ b/.github/ci/generated.sh
@@ -12,7 +12,7 @@ export CARGO_TARGET_DIR=/ci/cache/target
 hashtime restore /ci/cache/filetime.json || true
 hashtime save /ci/cache/filetime.json
 
-git clone https://github.com/embassy-rs/stm32-data-generated/ build
+git clone --depth 1 https://github.com/embassy-rs/stm32-data-generated/ build
 ./d ci
 
 COMMIT=$(git rev-parse HEAD)