4 files changed, 23 insertions, 2 deletions

diff --git a/embassy/Cargo.toml b/embassy/Cargo.toml
index 0e4c801bb..08d273dbb 100644
--- a/embassy/Cargo.toml
+++ b/embassy/Cargo.toml
@@ -5,7 +5,7 @@ authors = ["Dario Nieuwenhuis <[email protected]>"]
 edition = "2018"
 
 [features]
-std = ["futures/std"]
+std = ["futures/std", "rand_core"]
 defmt-trace = []
 defmt-debug = []
 defmt-info = []
@@ -16,6 +16,9 @@ defmt-error = []
 defmt = { version = "0.1.3", optional = true }
 log = { version = "0.4.11", optional = true }
 
+# std-only
+rand_core = { version = "0.5.1", optional = true, features = ["std"] }
+
 cortex-m = "0.6.4"
 futures     = { version = "0.3.5", default-features = false }
 pin-project = { version = "1.0.2", default-features = false }
diff --git a/embassy/src/rand.rs b/embassy/src/rand.rs
index 7e3788380..6e78c24ae 100644
--- a/embassy/src/rand.rs
+++ b/embassy/src/rand.rs
@@ -4,6 +4,9 @@ pub trait Rand {
     fn rand(&self, buf: &mut [u8]);
 }
 
+#[cfg(feature = "std")]
+static mut RAND: Option<&'static dyn Rand> = Some(&if_std::Rand);
+#[cfg(not(feature = "std"))]
 static mut RAND: Option<&'static dyn Rand> = None;
 
 pub unsafe fn set_rand(rand: &'static dyn Rand) {
@@ -13,3 +16,15 @@ pub unsafe fn set_rand(rand: &'static dyn Rand) {
 pub fn rand(buf: &mut [u8]) {
     unsafe { unwrap!(RAND, "No rand set").rand(buf) }
 }
+
+#[cfg(feature = "std")]
+mod if_std {
+    use rand_core::{OsRng, RngCore};
+
+    pub(crate) struct Rand;
+    impl super::Rand for Rand {
+        fn rand(&self, buf: &mut [u8]) {
+            OsRng.fill_bytes(buf)
+        }
+    }
+}
diff --git a/.cargo/config b/examples/.cargo/config
index 3f319ae55..3f319ae55 100644
--- a/.cargo/config
+++ b/examples/.cargo/config
diff --git a/test-build.sh b/test-build.sh
index ae603b289..52bf7bb7b 100755
--- a/test-build.sh
+++ b/test-build.sh
@@ -5,7 +5,10 @@ set -euxo pipefail
 # examples
 (cd examples; cargo build --target thumbv7em-none-eabi --bins)
 
-# embassy
+# embassy std
+(cd embassy; cargo build --features log,std)
+
+# embassy embedded
 (cd embassy; cargo build --target thumbv7em-none-eabi)
 (cd embassy; cargo build --target thumbv7em-none-eabi --features log)
 (cd embassy; cargo build --target thumbv7em-none-eabi --features defmt)