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1. 

   oliver
   Member

   Hello,
   i have been trying to write a Library, which sends me a Message over USB every few milliseconds ... but it does not work
   is Timer2 needed for USB Connection?

   - - - - - - - - - - - - - - - - - - -timerlib.h:

   #ifndef timerlib_h
#define timerlib_h

   #include "WProgram.h"

   void core();
void start();

   #endif

   - - - - - - - - - - - - - - - - - - - -timerlib.cpp:

   #include <timerlib.h>

   void core(void){

   SerialUSB.println("hello!");

   }

   void start(void){

   Timer2.setChannel1Mode(TIMER_OUTPUTCOMPARE);
Timer2.setPeriod(50000); // in microseconds
Timer2.setCompare1(1); // overflow might be small
Timer2.attachCompare1Interrupt(core);

   }

   Posted 4 years ago #
2. 

   gbulmer
   Moderator

   Have you tested flashing an LED instead of sending characters over USB?
   That is so simple, that it is likely to work.

   Typically there is a conflict between the interrupts, but an interrupt every 50 millisecond are so slow that it's likely some other problem.

   (full disclosure: I am not a member of LeafLabs staff)

   Posted 4 years ago #
3. 

   oliver
   Member

   Thanks for your answer i have tested it to switch on and off LED 13 and it Works fine.
   But as i add the Row:

   SerialUSB.println("huuu!");

   into the core function,
   The LED stops flickering and the Maple does not send.

   I've tested it with Timer1 - Timer4 and non of them does his Job

   50milliseconds is very slow so i think there is no Timer-conflict with sysclock or others

   Posted 4 years ago #
4. 

   gbulmer
   Moderator

   I agree, it is so slow that it isn't likely a timer conflict.

   Looking at your code, do you provide your own main() or do you use setup() and loop()? If you do provide your own main, are you calling all of the USB initialisation?

   If the LED works, and USB initialisation is taken care of, then I think the problem is trying to use SerialUSB within an interrupt service routine.

   There have been problems, but I thought it had been improved, so I don't understand why this causes any.

   My 'knee-jerk' is to reduce interaction with USB to a minimum. E.g. send only one character using print instead of println; maybe bel (0x07) if it makes a noise would do as a test. Characters will get flushed when the buffer fills, which isn't exactly what you want, but the problem needs to be hunted down first.

   (full disclosure: I am not a member of Leaflabs staff)

   Posted 4 years ago #
5. 

   poslathian
   LeafLabs

   first, make sure that you can send bytes over USB at all by throwing a SerialUSB.println("hi");delay(1000); into your main loop.

   next, try using the lower level usb routine to send bytes asynchronously:
   

   #include "usb.h"
   
   .
   .
   .
   uint8 sendBuf[5] = {1,2,3,4,5};
   uint32 bytes_sent = usbSendBytes(sendBuf,1); // send one byte nonblocking

   does that work?

   my *guess* is that since SerialUSB.print is a blocking send, your program is getting hung up on that function, and then the interrupt rolls around again, interrupting from the interrupt so to speak, and breaking things. you might try disabling the timer interrupt as the first thing in your timer interrupt, and then re-enabling it on the way out. you loose your 50ms guarantee, but this may be a helpful debugging element. ex:
   

   void core(void) {
      Timer1.Pause()
      // other code
      Timer1.Resume()
   }

   Posted 4 years ago #
6. 

   oliver
   Member

   Thank very much you for your answers, i've finally done it :)
   with usbSendBytes() it seems to work very well:

   here is the code without using a library:

   #include "usb.h"
int toggle = 0;

   uint8 sendBuf[7] = "Hallo\n";

   void core(void);

   void setup()
{

   pinMode(13, OUTPUT);
Timer2.setChannel1Mode(TIMER_OUTPUTCOMPARE);
Timer2.setPeriod(50000); // in microseconds
Timer2.setCompare1(1); // overflow might be small
Timer2.attachCompare1Interrupt(core);

   }

   void loop()
{

   delay(1);

   }

   void core(void){

   toggle ^= 1;
digitalWrite(13,toggle);
uint32 bytes_sent = usbSendBytes(sendBuf,6);

   }

   Posted 4 years ago #

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