Add Station.read-raw. (#29)

.github/workflows/ci.yml

@@ -13,9 +13,9 @@ jobs:
         os: [ ubuntu-latest, macos-latest ]
         # The versions should contain (at least) the lowest requirement
         #    and a version that is more up to date.
-        toit-version: [ v2.0.0-alpha.118, latest ]
+        toit-version: [ v2.0.0-alpha.144, latest ]
         include:
-          - toit-version: v2.0.0-alpha.118
+          - toit-version: v2.0.0-alpha.144
             version-name: old
           - toit-version: latest
             version-name: new

src/protocol.toit

@@ -74,6 +74,19 @@ class Response:
           --frame=frame
         throw exception
 
+class RawRequest extends Request:
+  payload/ByteArray
+  constructor function-code/int .payload:
+    super function-code
+  to-byte-array -> ByteArray:
+    return payload
+
+class RawResponse extends Response:
+  bits/ByteArray
+  constructor.deserialize frame/Frame function-code/int:
+    Response.check-frame_ function-code frame
+    bits = frame.data
+
 class ReadBitsRequest extends Request:
   static COILS-ID ::= 1
   static DISCRETE-INPUTS-ID ::= 2

src/station.toit

@@ -81,7 +81,7 @@ class Station:
     return holding-registers_
 
   /**
-  Reads the server identifaction.
+  Reads the server identification.
 
   This function is only available for serial Modbus devices, although it may also work on some Modbus TCP devices.
   */
@@ -94,6 +94,21 @@ class Station:
     server-response := response as ReportServerIdResponse
     return ServerIdResponse server-response.server-id server-response.on-off
 
+  /**
+  Reads a raw byte response for a specific $function-code.
+
+  The request may optionally include a $payload of bytes and the
+    result is the raw, unframed bytes in the server response.
+  */
+  read-raw --function-code/int --payload/ByteArray=#[] -> ByteArray:
+    if is-broadcast: throw "Can't read from broadcast station"
+    logger_.debug "read-raw" --tags={"unit_id": unit-id, "function_code": function-code}
+    request := RawRequest function-code payload
+    response := bus_.send_ request --unit-id=unit-id --is-broadcast=false:
+      RawResponse.deserialize it function-code
+    raw-response := response as RawResponse
+    return raw-response.bits
+
 /**
 A register reader for Modbus stations.