When I want to program a Teensy 3.5 micro-controller, I send it a .HEX file via a hardware serial port. I have two ways of doing this; one way is to use a serial comms app like Tera Term to send the file, and another way is via a small C# command-line app I wrote to do the same thing.
When I send a 3000+ line Hex file to the micro-controller, it takes approximately 14 seconds. When I do the same thing with my C# program, it takes twice as long (or longer!). The baud rate for both Tera Term and my C# program are the same, and of course the Teensy setup is common to both. When I looked as the serial transfer using a digital scope, I see the following (same time scale in both photos):
The first photo shows the transfer when using Tera Term, and the second one shows the transfer when using my C# program using Serial.WriteLine() to transfer file contents line-by-line, as shown below:
using System;
using System.IO;
using System.IO.Ports;
using System.Threading;
using System.Timers;
using System.Diagnostics;
/*
Small console app to facilitate over-the-air (OTA) updates to a Teensy 3.x/4.x controller,
using VS2019 with the Visual Micro extension as the Arduino IDE. It is called by a post-build
'hook' statement in a file called 'board.txt' located in whatever Teensy program is
being updated. This app does the following:
- Extract the project path and selected COMPORT number from the arguments to the call to Main()
- Opens a UART serial port connection to the Teensy, typically one provided by a BT adaptor
operating in 'pass-through' mode. The serial port COMPORT number is passed into this app
as an argument.
- Sends whatever command is required to put the existing Teensy firmware into 'update' mode
- Using the path of the updating program (passed in as an argument), locates the .HEX file
associated with the project, and sends it's contents to the Teensy, one line at a time, counting
lines and confirming checksums line-by-line
- Compares the number of lines sent to the Teensy with the number of lines received by the Teensy,
and if there is a match, allows the Teensy update process to complete; otherwise aborts
*/
namespace TeensyFlash
{
class Program
{
const string startCmdStr = "U"; //used in sketch's 'GetUserInput()' to start upload sequence
static string rcvStr = string.Empty;
private static System.Timers.Timer aTimer;
private static bool bTimedOut;
static void Main(string[] args)
{
//Extract the build path and selected COMPORT number from the arguments to the call to Main()
Console.WriteLine("Teensy Flash Console");
Console.WriteLine("Number of arguments in args = {0}\n", args.Length);
int argindex = 0;
string comPortStr = string.Empty;
foreach (var item in args)
{
Console.WriteLine(item);
if (item.Contains("COM"))
{
comPortStr = args[argindex];
}
argindex++;
}
string build_path = args[0];
string projectName = args[args.Length - 1];
projectName = projectName.Substring(0, projectName.Length - 4); //remove extension
build_path = build_path.Replace("\"", string.Empty).Trim();
string hexfilename = build_path + "\\" + projectName + ".hex";
Console.WriteLine("path = {0}", build_path);
Console.WriteLine("comport = {0}", comPortStr);
Console.WriteLine("build name = {0}", projectName);
Console.WriteLine("path to HEX file = {0}", hexfilename);
try
{
Stopwatch stopwatch = Stopwatch.StartNew();
string[] lines = System.IO.File.ReadAllLines(hexfilename);
foreach (string item in lines)
{
Console.WriteLine(item);
}
Console.WriteLine("this took " + stopwatch.ElapsedMilliseconds + " Msec");
}
catch (Exception)
{
throw;
}
Console.WriteLine("Opening Serial Port...");
try
{
SerialPort _serport = new SerialPort(comPortStr, 115200);
_serport.WriteTimeout = 1000;
_serport.WriteBufferSize = 20480;
_serport.Open();
_serport.DiscardOutBuffer();
_serport.DiscardInBuffer();
Thread.Sleep(100);
Console.WriteLine("Sending Trigger Character " + startCmdStr);
Console.WriteLine(startCmdStr);
_serport.Write(startCmdStr);
Console.WriteLine("Waiting for 'waiting' from Teensy...");
rcvStr = string.Empty;
aTimer = new System.Timers.Timer();
//aTimer.Interval = 5000;
aTimer.Interval = 25000;
aTimer.Elapsed += OnTimedEvent;
aTimer.Start();
while (!rcvStr.Contains("waiting") && !bTimedOut)
{
if (_serport.BytesToRead > 0)
{
rcvStr = _serport.ReadLine();
}
}
aTimer.Stop();
if (bTimedOut)
{
Console.WriteLine("Timed out waiting for 'waiting' response from Teensy");
}
else
{
//if we get to here, the Teensy is ready to receive HEX file contents
Console.WriteLine("Received " + rcvStr + " from Teensy");
Stopwatch stopwatch2 = Stopwatch.StartNew();
int numlines = 0;
string[] lines = System.IO.File.ReadAllLines(hexfilename);
foreach (string item in lines)
{
numlines++;
_serport.WriteLine(item);
}
Console.WriteLine("total lines = {0}, time = {1} mSec", numlines, stopwatch2.ElapsedMilliseconds);
//now we wait for Teensy to emit "hex file: xx lines xx bytes..." and then "enter xx to flash..."
aTimer.Start();
while (!rcvStr.Contains("hex file:") && !bTimedOut)
{
if (_serport.BytesToRead > 0)
{
rcvStr = _serport.ReadLine();
}
}
aTimer.Stop();
aTimer.Dispose();
if (bTimedOut)
{
Console.WriteLine("Timed out waiting for 'hex file' response from Teensy");
}
else
{
//extract number of lines from Teensy string, and compare with numlines.
//If they match, then send the number back to Teensy to complete the update.
//Otherwise, send '0' to abort
int colonIdx = rcvStr.IndexOf(':');
int lineIdx = rcvStr.IndexOf("lines");
string compareStr = rcvStr.Substring(colonIdx + 1, lineIdx - colonIdx - 1);
compareStr = compareStr.Trim();
int numTeensyLines = Convert.ToInt16(compareStr);
Console.WriteLine("sent {0} teensy replied {1}", numlines, numTeensyLines);
if (numTeensyLines == numlines)
{
Console.WriteLine("numlines {0} matches numTeensyLines {1} - send confirmation",
numlines, numTeensyLines);
_serport.WriteLine(compareStr);
}
}
}
}
catch (Exception)
{
throw;
}
try
{
}
catch (Exception)
{
throw;
}
}
static string chksum(string input)
{
int TwosComplement(string s)
{
if (s.Length % 2 != 0)
throw new FormatException(nameof(input));
var checksum = 0;
for (var i = 0; i < s.Length; i += 2)
{
var value = int.Parse(s.Substring(i, 2), System.Globalization.NumberStyles.AllowHexSpecifier);
checksum = (checksum + value) & 0xFF;
}
return 256 - checksum & 0xFF;
}
//return string.Concat(":", input, " ", TwosComplement(input).ToString("X2"));
return TwosComplement(input).ToString("X2");
}
private static void SetTimer()
{
// Create a timer with a two second interval.
aTimer = new System.Timers.Timer(2000);
// Hook up the Elapsed event for the timer.
aTimer.Elapsed += OnTimedEvent;
//aTimer.AutoReset = true;
aTimer.Enabled = true;
}
private static void OnTimedEvent(Object source, ElapsedEventArgs e)
{
Console.WriteLine("The Elapsed event was raised at {0:HH:mm:ss.fff}",
e.SignalTime);
bTimedOut = true;
}
}
}
The code that actually does the file transfer is:
Stopwatch stopwatch2 = Stopwatch.StartNew();
int numlines = 0;
string[] lines = System.IO.File.ReadAllLines(hexfilename);
foreach (string item in lines)
{
numlines++;
_serport.WriteLine(item);
}
Console.WriteLine("total lines = {0}, time = {1} mSec", numlines, stopwatch2.ElapsedMilliseconds);
When the '_serport.WriteLine(item);' line is commented out, the reported elapsed time is 0 mSec, as expected - so the 'ReadAllLines()' step isn't the problem.
Anyone have an idea why the 'WriteLine(item)' processing is so slow?