diff --git a/components/src/io_expander/pcf8574/pcf8574.adb b/components/src/io_expander/pcf8574/pcf8574.adb
new file mode 100644
index 000000000..8d94f770c
--- /dev/null
+++ b/components/src/io_expander/pcf8574/pcf8574.adb
@@ -0,0 +1,39 @@
+--
+--  Copyright 2022 (C) Rolf Ebert
+--
+--  SPDX-License-Identifier: BSD-3-Clause
+--
+
+
+package body PCF8574 is
+
+   -----------
+   --  Get  --
+   -----------
+
+   function Get (This : PCF8574_Module) return UInt8
+   is
+      Val    : I2C_Data (1 .. 1);
+      Status : I2C_Status;
+   begin
+      This.Port.Master_Receive (This.Addr, Val, Status);
+      return Val (1);
+   end Get;
+
+   procedure Get (This : PCF8574_Module; Data : out UInt8)
+   is begin
+      Data := Get (This);
+   end Get;
+
+   -----------
+   --  Set  --
+   -----------
+
+   procedure Set (This : PCF8574_Module; Data : UInt8)
+   is
+      Status : I2C_Status;
+   begin
+      This.Port.Master_Transmit (This.Addr, (1 => Data), Status);
+   end Set;
+
+end PCF8574;
diff --git a/components/src/io_expander/pcf8574/pcf8574.ads b/components/src/io_expander/pcf8574/pcf8574.ads
new file mode 100644
index 000000000..6cdcbeca0
--- /dev/null
+++ b/components/src/io_expander/pcf8574/pcf8574.ads
@@ -0,0 +1,38 @@
+--
+--  Copyright 2022 (C) Rolf Ebert
+--
+--  SPDX-License-Identifier: BSD-3-Clause
+--
+
+with HAL;        use HAL;
+with HAL.I2C;    use HAL.I2C;
+
+--  I2C 8-bit IO expander with quasi bidirectional I/O, no data
+--  direction, no latch
+
+package PCF8574 is
+
+   subtype PCF8574_Address is I2C_Address range 16#40# .. 16#5F#;
+
+   type PCF8574_Module (Port : not null Any_I2C_Port;
+                        Addr : I2C_Address) is tagged limited private;
+
+   type Any_PCF8574_Module is access all PCF8574_Module'Class;
+
+
+   procedure Set (This : PCF8574_Module; Data : UInt8);
+
+   function Get (This : PCF8574_Module) return UInt8;
+   procedure Get (This : PCF8574_Module; Data : out UInt8);
+   --  when reading the input from keys (buttons) carefully read the
+   --  datasheet. The input line should be set high before reading.
+   --  E.g. if all lines are key input:
+   --  M.Set (16#FF#);
+   --  Keys := M.Get;
+
+private
+
+   type PCF8574_Module (Port : not null Any_I2C_Port;
+                        Addr : I2C_Address) is tagged limited null record;
+
+end PCF8574;