A similar problem, but the microcontroller is different.
I want to try to connect without transceivers. (distance 2 meters)
Your example for OS2. Is it possible for OS5?
Yes, you can use PA_11 and PA_12 for CAN bus communication
...
CAN can(PA_11, PA_12);
...
But then I do not recommend to power the board over the USB connector because inside some USB chargers the USB_DP and USB_DM lines are connected one another. When such USB charger is used the CAN RD and CAN TD pins become connected one another (because the USB_DP and USB_DM pins are connected to the PA_11, PA_12 pins, respectively) and the CAN bus fails to operate.
For short distances you can omit CAN transceivers as described here. But then you probably have to reduce the CAN speed (frequency) to 500 000 bps (or less). And also make sure the grounds of the CAN nodes are connected one another.
Mbed OS 5 does not allow to call printf in ISR context so you have to use polling:
...
void onCanReceived(void)
{
//can.read(rxMsg);
pc.printf("-------------------------------------\r\n");
pc.printf("CAN message received\r\n");
printMsg(rxMsg);
...
}
int main(void)
{
pc.baud(9600); // set serial speed
can.frequency(500000); // set CAN bit rate to 500 000 bps
can.filter(RX_ID, 0xFFF, CANStandard, 0); // set filter #0 to accept only standard messages with ID == RX_ID
//can.attach(onCanReceived); // polling is used (in main() ) rather than ISR
#if defined(BOARD1)
led = ON; // turn the LED on
timer.start(); // start timer
pc.printf("CAN_Hello board #1\r\n");
#else
led = OFF; // turn LED off
pc.printf("CAN_Hello board #2\r\n");
#endif
while(1) {
if(can.read(rxMsg)) // polling for CAN messages
onCanReceived();
if(timer.read_ms() >= 2000) { // check for timeout
timer.stop(); // stop timer
timer.reset(); // reset timer
...
Здравствуйте Золтан.
Спасибо за ответ.
Ваши рекомендации мне очень помогли.
Я слабо владею английским, поэтому у меня просьба:
укажите что почитать на темы:
разница между OS2 и OS5;
как выбрать OS2 или OS5 в он-лайн компиляторе.
Большое спасибо за Вашу хорошую работу и внимание к MBED.
С уважением, Орьев Павел.
Hello Zoltan.
Thanks for the answer.
Your recommendations helped me a lot.
I do not speak much English, so I have a request:
indicate what to read on the topics:
the difference between OS2 and OS5;
How to choose OS2 or OS5 in an online compiler.
Thank you very much for your good work and attention to MBED.
It is very similar to Arduino. The main difference is a timer interrupt running at 1 MHz (on most platforms, on some low end ones it’s slower) that is used for all of the Timers/Tickers/Timeouts to give a 1 us resolution.
RTOS isn’t available by default but can be added like a library.
Suitable for smaller target MCUs. However, more recent ones are not supported.
RTOS is on by default. For small targets (or if you don’t want to use it) you can turn it off by adding a mbed_app.json file with the following content to the project:
I have received a private message from you. But I’m not able to send a reply via the Mbed messaging system because it says “This user’s profile page is private”. So here is your question and my response:
It is not a typo. It is valid only for STM targets where in Open Drain Mode a “0” in the Output register activates the N-MOS while a “1” in the output register leaves the port in Hi-Z (the P-MOS is never activated). A read access to the Input Data Register gets the I/O state in open drain mode.
NOTE: The ‘\’ after the output(); tells the C-preprocessor that the macro continues on the following line
The MODE() macro is then used in OneWire.cpp :
OneWire::OneWire(PinName pin) :
DigitalInOut(pin)
{
MODE(); // set mode to either OpenDrain for STM or PullUp for others
INIT_WAIT;
#if ONEWIRE_SEARCH
reset_search();
#endif
}
When the C-preprocessor is run it replaces the MODE() and the INIT_WAIT macros in accordance with their’s definition:
OneWire::OneWire(PinName pin) :
DigitalInOut(pin)
{
output();
mode(OpenDrain); // set mode to either OpenDrain for STM or PullUp for others
; // INIT_WAIT is replaced with empty text
#if ONEWIRE_SEARCH
reset_search();
#endif
}
