Rather than post hundreds of lines of C++ Builder code that you could build to illustrate data transfers that take only a few dozen lines, I bit the bullet and came up with a couple of Python scripts. The first script opens a file, then reads the data and sends it to the Teensy on one of the USB Serial connections. The T4.x stuffs the incoming data into a buffer (in DMAMEM in the example).
A second Python script asks the T4.x to return the data from the buffer and the script writes the data to a new file. I used a .bmp image file for testing because is was easy to check for errors by looking at the returned file. The Pythons scripts are very simple--I only have about 15 hours of Python programming experience--and a lot of that was spent stumbling around the internet looking for example code. The Teensy program that talks to the Python scripts is a bit more refined--but then I've got about a thousand times more hours with C and C++ than with Python.
This Python script sends the file to the Teensy 4.x:
Code:
# Send a file to Teensy in binary format
# I'm using a .bmp file in the example
# because it's easy to look at the returned data
# and see if it has survived the round trip to the
# Teensy and back
import serial
from os.path import getsize
## You will need to make sure which PC Comm Ports are
## used in your system and adjust the comm port numbers
## If you're using IOS or Linux, I hope you know how to
## make the changes----I sure don't!
datport = serial.Serial('COM9', 115200, timeout=5)
ctlport = serial.Serial('COM10', 115200, timeout=3.5)
print("Serial ports open");
ctlport.write(b'r') # tell the teensy that data is coming
fname = "test.bmp" # change the following for your own test file
binfile = open(fname, 'rb')
filesize = getsize(fname)
print("File Size: ", filesize)
datport.write(filesize.to_bytes(4,byteorder='little'))
## Read the whole file and write it in one line! Nice!
datport.write(binfile.read())
binfile.close()
print("Sent " , fname);
##*****************************************************
##optional request to have teensy play back first part of
##buffer data.
##ctlport.write(b'p') # tell the teensy to send buffer data
##print("Requesting buffer playback")
ch = b' '
while(ch.decode() != 'q'):
ch = ctlport.read(1)
print(ch.decode(), end='')
print("Program ended with received <q>");
datport.close()
ctlport.close()
print("Serial ports closed.");
This Python script asks the Teensy 4.x to send back the data sent by the first script. It writes the received data to a different file for later comparison:
Code:
# Receive a data buffer from the Teensy and write to file
# I'm receiving from a .bmp file in the example
# because it's easy to look at the returned data
# and see if it has survived the round trip to the
# Teensy and back
import serial
from os.path import getsize
## You will need to make sure which PC Comm Ports are
## used in your system and adjust the comm port numbers
## If you're using IOS or Linux, I hope you know how to
## make the changes----I sure don't!
datport = serial.Serial('COM9', 115200, timeout=0.5)
ctlport = serial.Serial('COM10', 115200, timeout=3.5)
print("Serial ports open");
ctlport.write(b's') # tell the teensy to send data
fname = "rcvtest.bmp" # get back 154KB QVGA RGB565 test file
binfile = open(fname, 'wb')
blocksize = 4096
## Teensy will tell us how many bytes to expect
mybytes = bytearray([0,0,0,0])
## Read 4 bytes from Teensy to get # bytes to expect
mybytes = datport.read(4)
filesize = int.from_bytes(mybytes,"little")
bytesleft = filesize
print("Data length is ",filesize, " bytes")
while (bytesleft > 0):
if bytesleft > blocksize:
bytestoread = blocksize
else:
bytestoread = bytesleft
## Read and write a block all in one line! Nice!
binfile.write(datport.read(bytestoread))
bytesleft = bytesleft - bytestoread
binfile.close()
## Now we read and display anything the Teensy sent before <q>
ch = b' '
while(ch.decode() != 'q'):
ch = ctlport.read(1)
print(ch.decode(), end='') # no EOL after each character
print("Program ended with received <q>");
datport.close()
ctlport.close()
print("Serial ports closed.");
print("Saved to " , fname);
datport.close()
ctlport.close()
print("Serial ports closed.");
Here is the Teensy sketch that responds to the PC and transfers data over the second USB serial connection:
Code:
/**************************************
* Minimal binary transfer using 2 serial channels
* control channel receives requests to send or receive
* data channel sends or receives binary data
* This program is written for T4X and saves buffered
* data in either DMAMEM or EXTMEM
*/
const int ledpin = 13;
#define LEDON digitalWriteFast(ledpin, HIGH);
#define LEDOFF digitalWriteFast(ledpin, LOW);
#define BUFFSIZE 300*1024
uint8_t buffer[BUFFSIZE] DMAMEM;
elapsedMillis trtimer = 0;
void setup() {
Serial.begin(9600); // the control channel
SerialUSB1.begin(9600); // the data channel
delay(400);
pinMode(ledpin, OUTPUT);
Serial.println("Sending q");
memset(buffer, 0x44,BUFFSIZE);
}
// This global gets set by RcvBuffer call
uint32_t rcvbytes = 100;
void loop() {
char ch;
if (Serial.available()) {
ch = Serial.read();
switch (ch) {
case 's' :
SendBuffer(rcvbytes);
break;
case 'r' :
rcvbytes = RcvBuffer();
break;
} // end of switch(ch)
} // end of if(Serial.available())
}
void SendBuffer(uint32_t numbytes){
uint32_t datlen, endmillis;
float frate;
LEDON
trtimer = 0;
datlen = numbytes;
// Tell the PC how many bytes to expect
SerialUSB1.write((uint8_t *)&datlen,4);
// Now send the bytes from the buffer
// I write the whole thing in one chunk---just because I can!
SerialUSB1.write((unsigned char *)&buffer[0], datlen);
LEDOFF
endmillis = trtimer;
Serial.printf("Teensy Sent %lu bytes in %lu mSec ", datlen,endmillis);
frate = (float)datlen/1024.0/(endmillis /1024.0);
Serial.printf(" or %6.1f KBytes/Second\n", frate);
Serial.println("q");
}
// RcvBuffer expects a 4-byte unsigned long indicating the
// number of bytes to receive, then that many following
// bytes. The data is stored in buffer.
#define TIMEOUT 2000
uint32_t RcvBuffer(void){
uint32_t datlen, dcount, endmillis;
float frate;
dcount = 0;
do {
delay(1);
dcount ++;
} while((dcount <TIMEOUT) && (SerialUSB1.available()<4));
if(dcount >= TIMEOUT) {
Serial.println("Timeout waiting for data\n");
Serial.println("q"); // tells PC that we're done
return 0;
}
LEDON
trtimer = 0;
SerialUSB1.readBytes((char *)&datlen,4);
if(datlen > BUFFSIZE) datlen = BUFFSIZE;
// now read the data into buffer
SerialUSB1.readBytes((char *)&buffer, datlen);
endmillis = trtimer;
LEDOFF
Serial.printf("Teensy Received %lu bytes in %lu mSec. ", datlen,endmillis);
frate = (float)datlen/1024.0/(endmillis /1024.0);
Serial.printf(" or %6.1f KBytes/Second\n", frate);
// Uncomment the next line to have the teensy echo back 200 bytes
// PlayBuffer();
Serial.print("\nq");// Tell PC we're done
return datlen;
}
// Send back some buffer contentsin hex format over the control USB Serial link
void PlayBuffer(void){
uint16_t i;
for(i= 0; i< 200; i++){
Serial.printf("%02X ",buffer[i]);
}
Serial.println("Playback done. q");
}
The Teensy sketch sends back some timing data on the transfers---but I'm not sure how how much to rely on the indicated speeds. Both the Teensy 4.x and the PC could be moving data around with DMA many milliseconds after they tell you they are finished.
Here's what the Idle shell reported with one set of transfers:
Code:
===================== RESTART: C:\Users\User\Python39\sendfile.py =====================
Serial ports open
File Size: 154178
Sent test.bmp
Teensy Received 154178 bytes in 5 mSec. or 30835.6 KBytes/Second
qProgram ended with received <q>
Serial ports closed.
>>>
====================== RESTART: C:/Users/User/Python39/rcvfile.py =====================
Serial ports open
Data length is 154178 bytes
Teensy Sent 154178 bytes in 4 mSec or 38544.5 KBytes/Second
qProgram ended with received <q>
Serial ports closed.
Saved to rcvtest.bmp
Serial ports closed.
>>>
Now that I've satisfied my curiosity about whether Python can be used for USB data transfers, I'll see if I can write similar routines to do the same thing in C++builder without all the GUI overhead. It's been a decade or more since I wrote a non-GUI app with C++builder, so that ought to be an interesting experience.
Originally Posted by weedogt
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