Hello,
a few days ago I decided to make a simple oscilloscope with my due and being the way I am, I wanted maximum sampling frequency which in turn demanded fast communication with my PC. I've been at it a while now, looking for solutions, but it turns out there isn't much documentation on this matter. Anyway, I managed to put something together and due to the lack of information on the internet I will share my project on this forum so it may help a fellow due user. Also, I will aprpeciate hints and ideas for improvments or other solutions anyone might think of or has already done so in the past.
To clarify, this is simply one way to use the due's native usb port to communicate with your pc at high speeds.
This is some simple arduino code to generate output:
uint16_t buf[256];
void setup() {
SerialUSB.begin(9600);
while(!SerialUSB);
for(int i = 0; i < 256; i++)
buf[i] = (uint16_t)i;
}
void loop() {
SerialUSB.write((uint8_t*)buf, 512);
}
Note: the specified baud rate at SerialUSB.begin(baud) is irrelevant, you can also set it to 0. As far as I know this is because the communication will always run at maximum speed the two devices can handle. So instead of sending data constantly at a slower rate it will send the data at higher speeds in packets. I would like for someone who knows this in more detail to confirm(or not) this and write a short classification of all the parts(protocol, communication,...) at work here since I can't even name the protocol that is being used. (help)
With the arduino side complete, there are many ways to read the data from the serial port on your PC. I wanted a simple solution for this, but I couldn't get things to work with Processing, I believe this was because with SerialUSB arduino doesn't get reset when you open the port on the PC side (help!).
Nor did I manage to use python, because I had some library problems.
Next was C#, which worked, but I wanted to be able to access the code in C++ so I created a dll in C# and then failed to use it in C++.
And lastly I turned to C++ alone. Now I copied most of this code from Arduino Playground, I just changed it a bit to make it work the way I wanted it to.
Link: Arduino Playground - CPPWindows
Code:
Serial.h
#ifndef SERIALCLASS_H_INCLUDED
#define SERIALCLASS_H_INCLUDED
#define ARDUINO_WAIT_TIME 2000
#include <windows.h>
#include <stdio.h>
#include <stdlib.h>
class Serial
{
private:
//Serial comm handler
HANDLE hSerial;
//Connection status
bool connected;
//Get various information about the connection
COMSTAT status;
//Keep track of last error
DWORD errors;
public:
//Initialize Serial communication with the given COM port
Serial(char *portName);
//Close the connection
~Serial();
//Read data in a buffer, if nbChar is greater than the
//maximum number of bytes available, it will return only the
//bytes available. The function return -1 when nothing could
//be read, the number of bytes actually read.
int ReadData(char *buffer, unsigned int nbChar, unsigned int *queue);
//Writes data from a buffer through the Serial connection
//return true on success.
bool WriteData(char *buffer, unsigned int nbChar);
//Check if we are actually connected
bool IsConnected();
};
#endif // SERIALCLASS_H_INCLUDED
Serial.cpp
#include "Serial.h"
Serial::Serial(char *portName)
{
//We're not yet connected
this->connected = false;
//Try to connect to the given port throuh CreateFile
this->hSerial = CreateFile(portName,
GENERIC_READ | GENERIC_WRITE,
0,
NULL,
OPEN_EXISTING,
FILE_ATTRIBUTE_NORMAL,
NULL);
//Check if the connection was successfull
if (this->hSerial == INVALID_HANDLE_VALUE)
{
//If not success full display an Error
if (GetLastError() == ERROR_FILE_NOT_FOUND) {
//Print Error if neccessary
printf("ERROR: Handle was not attached. Reason: %s not available.\n", portName);
}
else
{
printf("ERROR!!!");
}
}
else
{
//If connected we try to set the comm parameters
DCB dcbSerialParams = { 0 };
//Try to get the current
if (!GetCommState(this->hSerial, &dcbSerialParams))
{
//If impossible, show an error
printf("failed to get current serial parameters!");
}
else
{
//Define serial connection parameters for the arduino board
dcbSerialParams.BaudRate = CBR_9600;
dcbSerialParams.ByteSize = 8;
dcbSerialParams.StopBits = ONESTOPBIT;
dcbSerialParams.Parity = NOPARITY;
//Setting the DTR to Control_Enable ensures that the Arduino is properly
//reset upon establishing a connection
dcbSerialParams.fDtrControl = DTR_CONTROL_ENABLE;
//Set the parameters and check for their proper application
if (!SetCommState(hSerial, &dcbSerialParams))
{
printf("ALERT: Could not set Serial Port parameters");
}
else
{
//If everything went fine we're connected
this->connected = true;
//Flush any remaining characters in the buffers
PurgeComm(this->hSerial, PURGE_RXCLEAR | PURGE_TXCLEAR);
//We wait 2s as the arduino board will be reseting
Sleep(ARDUINO_WAIT_TIME);
}
}
}
}
Serial::~Serial()
{
//Check if we are connected before trying to disconnect
if (this->connected)
{
//We're no longer connected
this->connected = false;
//Close the serial handler
CloseHandle(this->hSerial);
}
}
int Serial::ReadData(char *buffer, unsigned int nbChar, unsigned int *queue)
{
//Number of bytes we'll have read
DWORD bytesRead;
//Use the ClearCommError function to get status info on the Serial port
ClearCommError(this->hSerial, &this->errors, &this->status);
*queue = (unsigned int)status.cbInQue;
//Check if there is something to read
if (this->status.cbInQue>nbChar)
{
//Try to read the required number of chars, and return the number of read bytes on success
if (ReadFile(this->hSerial, buffer, nbChar, &bytesRead, NULL))
{
return bytesRead;
}
}
//If nothing has been read, or that an error was detected return 0
return 0;
}
bool Serial::WriteData(char *buffer, unsigned int nbChar)
{
DWORD bytesSend;
//Try to write the buffer on the Serial port
if (!WriteFile(this->hSerial, (void *)buffer, nbChar, &bytesSend, 0))
{
//In case it don't work get comm error and return false
ClearCommError(this->hSerial, &this->errors, &this->status);
return false;
}
else
return true;
}
bool Serial::IsConnected()
{
//Simply return the connection status
return this->connected;
}
main.cpp
#include <stdio.h>
#include <tchar.h>
#include "Serial.h" // Library described above
#include <string>
#include <time.h>
// application reads from the specified serial port and reports the collected data
int main(int argc, char* argv[])
{
printf("Welcome to the serial test app!\n\n");
Serial* SP = new Serial("COM4"); // adjust as needed
if (SP->IsConnected())
printf("We're connected");
char incomingData[512] = ""; // don't forget to pre-allocate memory
unsigned short data[256]; //printf("%s\n",incomingData);
int dataLength = 512;
clock_t clk = clock();
unsigned int que, read = 0, total = 0;
while (SP->IsConnected())
{
if (SP->ReadData(incomingData, dataLength, &que)) {
for (int i = 0; i < 256; i++) {
data[i] = incomingData[2 * i + 1] << 8 | (incomingData[2 * i] & 0xFF);
}
read += 512;
}
if (clock() - clk > CLOCKS_PER_SEC) {
system("cls");
total += read;
printf("Bytes read so far: %u B\nCurrent communication speed: %u B/s\nBytes in queue: %u B\n\n", total, read, que);
read = 0;
clk = clock();
}
//Sleep(100);
}
return 0;
}
There are some imperfections in what I supplied, but that's because I have just made it work and I was eager to share it.
Questions and answers welcome!
