// Copyright 2015 Christian d'Heureuse, Inventec Informatik AG, Zurich, Switzerland
// www.source-code.biz, www.inventec.ch/chdh
//
// This module is multi-licensed and may be used under the terms of any of the following licenses:
//
//  LGPL, GNU Lesser General Public License, V2.1 or later, http://www.gnu.org/licenses/lgpl.html
//  EPL, Eclipse Public License, V1.0 or later, http://www.eclipse.org/legal
//
// Please contact the author if you need another license.
// This module is provided "as is", without warranties of any kind.
//
// Home page: http://www.source-code.biz/snippets/java/SerialPortChannel

package biz.source_code.utils;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;

/**
* A serial port channel channel for BeagleBone.
*/
public class SerialPortChannelBeagleBone extends SerialPortChannel {

private static final String portNamePrefix = "/dev/ttyO";

public static boolean isPortAccessible (String portNo) {
   File file = new File(portNamePrefix + portNo);
   return file.exists() && file.canRead() && file.canWrite(); }

/**
* Creates a serial port channel.
*
* @param portNo
*   The serial port number, e.g. "2" (for "/dev/ttyO2").
* @param baudRate
*   The baud rate for the serial port, e.g. 9600.
*/
public SerialPortChannelBeagleBone (String portNo, int baudRate) throws IOException {
   super(portNamePrefix + portNo, baudRate);
   try {
      setBeagleBoneRegisters(portNo); }
   catch (Exception e) {
      System.err.println("Warning: Unable to set BeagleBone registers. " + e); }}

// Sets registers of the AM335X processor to configure the serial port i/o pins.
// This is only necessary for Android distributions where the serial ports are not already pre-configured.
// It may also be necessary to change the file system permissions, e.g. in init.rc:
//  chmod 666 /dev/ttyO1
//  chmod 666 /dev/ttyO2
//  chmod 666 /dev/ttyO4
//  chmod 666 /dev/ttyO5
//  chmod 222 /sys/kernel/debug/omap_mux/uart1_rxd
//  chmod 222 /sys/kernel/debug/omap_mux/uart1_txd
//  chmod 222 /sys/kernel/debug/omap_mux/spi0_sclk
//  chmod 222 /sys/kernel/debug/omap_mux/spi0_d0
//  chmod 222 /sys/kernel/debug/omap_mux/gpmc_wait0
//  chmod 222 /sys/kernel/debug/omap_mux/gpmc_wpn
//  chmod 222 /sys/kernel/debug/omap_mux/lcd_data9
//  chmod 222 /sys/kernel/debug/omap_mux/lcd_data8
private static void setBeagleBoneRegisters (String channel) throws IOException {
   if (channel.equals("1")) {
      writeReg("uart1_rxd",  20);
      writeReg("uart1_txd",   0); }
   else if (channel.equals("2")) {
      writeReg("spi0_sclk",  21);
      writeReg("spi0_d0",     1); }
   else if (channel.equals("4")) {
      writeReg("gpmc_wait0", 26);
      writeReg("gpmc_wpn",    6); }
   else if (channel.equals("5")) {
      writeReg("lcd_data9",  24);
      writeReg("lcd_data8",   4); }
   else {
      throw new IOException("Unsupported BeagleBone serial port channel " + channel + "."); }}

private static void writeReg (String regName, int regValue) throws IOException {
   FileOutputStream f = null;
   try {
      f = new FileOutputStream("/sys/kernel/debug/omap_mux/" + regName);
      f.write(Integer.toString(regValue).getBytes());
      f.flush(); }
   finally {
      if (f != null) {
         f.close(); }}}

}