diff --git a/src/engine.rs b/src/engine.rs
index e786b2f..8c35397 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -18,10 +18,16 @@ struct InputEngineDevice {
 }
 
 pub fn build_input_engine_device(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+}
+
+pub fn build_input_engine_device_rusb(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
    let _device_cfg = cfg.device.as_ref().unwrap();
 
    assert!(rusb::has_capability());
+
    let ctx = rusb::Context::new().unwrap();
+   assert!(ctx.devices().unwrap().len() > 0);
+
    for device in ctx.devices().unwrap().iter() {
        let device_desc = device.device_descriptor().unwrap();
        println!("Bus {:03} Device {:03} ID {:04x}:{:04x}",