From 0bc708839d2295cb5638dee97b53452ed05233e5 Mon Sep 17 00:00:00 2001
From: clinton <clinton.freeman@gmail.com>
Date: Thu, 29 Sep 2016 21:44:03 +1000
Subject: [PATCH] added support for the pcal9535

---
 controller/pcal9535a/pcal9535a.go | 43 +++++++++++++++++++++++++++++++
 1 file changed, 43 insertions(+)
 create mode 100644 controller/pcal9535a/pcal9535a.go

diff --git a/controller/pcal9535a/pcal9535a.go b/controller/pcal9535a/pcal9535a.go
new file mode 100644
index 0000000..7dad5a9
--- /dev/null
+++ b/controller/pcal9535a/pcal9535a.go
@@ -0,0 +1,43 @@
+// PCAL953A, low volage GPIO expander as found in the Raspberry
+// Pi Relay board by Seeed Studio.
+//
+// http://wiki.seeedstudio.com/wiki/Raspberry_Pi_Relay_Board_v1.0
+package pcal9535a
+
+import (
+	"github.com/kidoman/embd"
+)
+
+const (
+	REG_MODE = 0x06
+)
+
+type PCAL9535A struct {
+	Bus  embd.I2CBus
+	Addr byte
+	D    byte
+}
+
+// New creates and connects to a PCAL9535A GPIO expander.
+func New(bus embd.I2CBus, addr byte) (*PCAL9535A, error) {
+	return &PCAL9535A{
+		Bus:  bus,
+		Addr: addr,
+		D:    0xff,
+	}, bus.WriteByteToReg(addr, REG_MODE, 0xff)
+}
+
+// Sets the nominated GPIO pin to either high (on = true) or low (on = false)
+func (c *PCAL9535A) SetPin(pin uint, on bool) error {
+	if on {
+		c.D &= ^(byte(0x1) << pin)
+	} else {
+		c.D |= (byte(0x1) << pin)
+	}
+
+	return c.Bus.WriteByteToReg(c.Addr, REG_MODE, c.D)
+}
+
+func (c *PCAL9535A) GetPin(pin uint) bool {
+	return (((c.D >> pin) & 1) == 0)
+}