Added display printing util function

uncanny/display.go

@@ -0,0 +1,52 @@
+package uncanny
+
+import (
+	"errors"
+	"fmt"
+	"golang.org/x/text/encoding/charmap"
+)
+
+// encodeString encodes a Unicode string into a given charmap.
+// Unsupported characters are replaced by the default replacement symbol.
+// Mysteriously, this functionality is missing from x/text/encoding.
+// TODO Implement the custom NEC display encoding.
+func encodeString(s string) ([]byte) {
+	ret := make([]byte, len(s))
+	for i, c := range(s) {
+		ret[i], _ = charmap.ISO8859_1.EncodeRune(c)
+	}
+	return ret
+}
+
+func (c *Can) DisplayWrite(line int, a []byte) error {
+	var addr int
+	switch line {
+	case 0:
+		addr = 0x80
+	case 1:
+		addr = 0xc0
+	default:
+		return errors.New("Invalid line")
+	}
+	// print in 3 chunks, as one frame is limited to 8 bytes
+	// the display has only 16 characters per line, so we truncate there
+	if len(a) > 0 {
+		return c.bus.Publish(DisplayCommand{addr, a[:7]}.Encode())
+	}
+	if len(a) > 7 {
+		return c.bus.Publish(DisplayCommand{addr, a[7:14]}.Encode())
+	}
+	if len(a) > 14 {
+		return c.bus.Publish(DisplayCommand{addr, a[14:16]}.Encode())
+	}
+	return nil
+}
+
+func (c *Can) DisplayPrint(line int, a string) error {
+	return c.DisplayWrite(line, encodeString(a))
+}
+
+func (c *Can) DisplayPrintf(line int, a string, args ...interface{}) error {
+	s := fmt.Sprintf(a, args...)
+	return c.DisplayPrint(line, s)
+}

uncanny/go.mod

@@ -2,4 +2,7 @@ module git.kabelsalat.ch/ccc-basel/matemat
 
 go 1.11
 
-require github.com/brutella/can v0.0.1
+require (
+	github.com/brutella/can v0.0.1
+	golang.org/x/text v0.3.6
+)

uncanny/go.sum

@@ -2,3 +2,6 @@ github.com/brutella/can v0.0.1 h1:Rz+2Zuje3NT79daon8wPN9+VphH3/kl1DP8Dhf/k1NI=
 github.com/brutella/can v0.0.1/go.mod h1:NYDxbQito3w4+4DcjWs/fpQ3xyaFdpXw/KYqtZFU98k=
 golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06 h1:0oC8rFnE+74kEmuHZ46F6KHsMr5Gx2gUQPuNz28iQZM=
 golang.org/x/sys v0.0.0-20181213200352-4d1cda033e06/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
+golang.org/x/text v0.3.6 h1:aRYxNxv6iGQlyVaZmk6ZgYEDa+Jg18DxebPSrd6bg1M=
+golang.org/x/text v0.3.6/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
+golang.org/x/tools v0.0.0-20180917221912-90fa682c2a6e/go.mod h1:n7NCudcB/nEzxVGmLbDWY5pfWTLqBcC2KZ6jyYvM4mQ=