diff --git a/beautiful-racket/br/demo/hdl/Nand.hdl.rkt b/beautiful-racket/br/demo/hdl/Nand.hdl.rkt
index ce89334..c777a99 100644
--- a/beautiful-racket/br/demo/hdl/Nand.hdl.rkt
+++ b/beautiful-racket/br/demo/hdl/Nand.hdl.rkt
@@ -1,6 +1,6 @@
 #lang br
 (provide (prefix-out Nand- (all-defined-out)))
-(require "helper.rkt")
+(require "bus.rkt")
 
 (define-input-bus a)
 (define-input-bus b)
diff --git a/beautiful-racket/br/demo/hdl/bus-properties.rkt b/beautiful-racket/br/demo/hdl/bus-properties.rkt
new file mode 100644
index 0000000..e322198
--- /dev/null
+++ b/beautiful-racket/br/demo/hdl/bus-properties.rkt
@@ -0,0 +1,11 @@
+#lang br
+(provide (all-defined-out))
+
+(define-values (bus bus? bus-get)
+  (make-impersonator-property 'bus))
+
+(define-values (output-bus output-bus? output-bus-get)
+  (make-impersonator-property 'output-bus))
+
+(define-values (input-bus input-bus? input-bus-get)
+  (make-impersonator-property 'input-bus))
\ No newline at end of file
diff --git a/beautiful-racket/br/demo/hdl/helper.rkt b/beautiful-racket/br/demo/hdl/bus.rkt
similarity index 96%
rename from beautiful-racket/br/demo/hdl/helper.rkt
rename to beautiful-racket/br/demo/hdl/bus.rkt
index 152d0e0..2882ee8 100644
--- a/beautiful-racket/br/demo/hdl/helper.rkt
+++ b/beautiful-racket/br/demo/hdl/bus.rkt
@@ -1,5 +1,5 @@
 #lang br
-(require racket/list (for-syntax br/syntax) racket/splicing)
+(require racket/list (for-syntax br/syntax) racket/splicing "bus-properties.rkt")
 (provide (all-defined-out))
 
 (module+ test
@@ -101,8 +101,6 @@ base bus:
 |#
 
 
-(define-values (bus bus? bus-get)
-  (make-impersonator-property 'bus))
 
 (define-macro-cases define-base-bus
   [#'(_macro-name ID THUNK) #'(_macro-name ID THUNK default-bus-width)]
@@ -156,8 +154,8 @@ output bus:
 + cannot write
 |#
 
-(define-values (output-bus output-bus? output-bus-get)
-  (make-impersonator-property 'output-bus))
+
+
 
 (define-macro (define-output-bus . _args)
   (syntax-property #'(define-base-bus . _args) 'impersonate #'output-bus))
@@ -188,8 +186,6 @@ input bus:
 + can write all, or bits
 |#
 
-(define-values (input-bus input-bus? input-bus-get)
-  (make-impersonator-property 'input-bus))
 
 (define-macro-cases define-input-bus
   [#'(_macro-name _id)
diff --git a/beautiful-racket/br/demo/hdl/expander.rkt b/beautiful-racket/br/demo/hdl/expander.rkt
index 9f2bbed..f8edb24 100644
--- a/beautiful-racket/br/demo/hdl/expander.rkt
+++ b/beautiful-racket/br/demo/hdl/expander.rkt
@@ -1,5 +1,5 @@
 #lang br
-(require "helper.rkt" (for-syntax racket/syntax racket/require-transform br/syntax "helper.rkt"))
+(require "bus.rkt" (for-syntax racket/syntax racket/require-transform br/syntax "bus-properties.rkt"))
 (provide #%top-interaction #%module-begin #%app #%datum (all-defined-out))
 
 (define-macro (chip-program CHIPNAME
@@ -21,13 +21,13 @@
 (define-macro (part PARTNAME ((BUS-LEFT . BUS-LEFT-ARGS) BUS-RIGHT-EXPR) ...)
   (with-pattern
    ([(PARTNAME-BUS-LEFT ...) (prefix-id #'PARTNAME "-" #'(BUS-LEFT ...))]
-    [CHIP-MODULE-PATH (format-string "~a.hdl.rkt" #'PARTNAME)])
+    [PARTNAME-MODULE-PATH (format-string "~a.hdl.rkt" #'PARTNAME)])
    #'(begin
-       (require (import-chip CHIP-MODULE-PATH)
+       (require (import-chip PARTNAME-MODULE-PATH)
                 ;; need for-syntax to make phase 1 binding available
                 ;; so we can determine during expansion which buses are `input-bus?`
                 ;; because the pin-spec syntax is inherently ambiguous
-                (for-syntax (import-chip CHIP-MODULE-PATH))) 
+                (for-syntax (import-chip PARTNAME-MODULE-PATH))) 
        (handle-buses ((PARTNAME-BUS-LEFT . BUS-LEFT-ARGS) BUS-RIGHT-EXPR) ...))))
 
 
@@ -46,7 +46,7 @@
                                [((PREFIXED-WIRE . _) _)
                                 ;; we "pre-evaluate" #'PREFIXED-WIRE so we can set up the program correctly.
                                 ;; This is not ideal: usually we want evaluate runtime expressions only at runtime.
-                                ;; But in this case, it controls which identifiers we `define`
+                                ;; But in this case, it controls which identifiers we `define` as output buses
                                 ;; so there's no way around it. Runtime would be too late.
                                 (input-bus? (syntax-local-eval #'PREFIXED-WIRE))])])
     (with-pattern