Good afternoon, I would like to know how I could use pins D0 and D1 of my NUCLEO STM32-F401RE board as PWMs, because by default it comes as a virtual communication port STLink. I would change it for UART6, PC_6 (UART6_TX) and PA_12 (UART_RX).
I read that you have to close the SB62 / SB63 and open the SB13 / SB14 welding jumpers on the board and I have done it, but it still does not work, you may have to change some of the mbed configuration, but I do not know what .
I attached the code that I have with which I do my tests:
#include “mbed.h”
PwmOut servo (PA_3);
Serial my_serial (PC_6, PA_12);
int main () {
servo.period_us (20000);
int servopulsewidth = 1500;
int pata_si = 1200;
int pata_no = 1900;
bool mov = false;
servo.pulsewidth_us (servopulsewidth);
while (1) {
if (mov == true) {
servo.pulsewidth_us (pata_si);
my_serial.printf ("Hello! \ n", servo.read ());
} else {
servo.pulsewidth_us (pata_no);
}
mov =! mov;
wait_ms (250);
}
Essentially, what you will want to do is create an mbed_app.json file in the root of your Mbed OS project. Copy and paste the following code into the mbed_app.json file:
You will also need to connect the PC_6 via a jumper wire to the CN3-RX pin and the PA_12 pin to the CN3-TX pin. I’ve done this on my board as shown in the image below (the red wire connects PC_6 to CN3-RX and the green wire connects PA_12 to CN3-TX):
I’ve also updated your code to print out the value of the PwmOut pin in the printf call, here’s the updated code:
#include "mbed.h"
PwmOut servo(PA_3);
Serial my_serial(PC_6, PA_12);
int main() {
servo.period_us(20000);
int servopulsewidth = 1500;
int pata_si = 1200;
int pata_no = 1900;
bool mov = false;
servo.pulsewidth_us(servopulsewidth);
while(1) {
if (mov == true) {
servo.pulsewidth_us(pata_si);
my_serial.printf("Read: %f\r\n", servo.read());
} else {
servo.pulsewidth_us(pata_no);
}
mov = !mov;
wait_ms(250);
}
}
Then compile your program and flash it to the board. Connect to your board via a serial terminal viewer using the 9600 baud rate and you should see output similar to the screenshot below:
Good morning, I have a question when creating the file mbed_app.json. I have my program called "Nucleo_pwm" and I have created the file "mbed_app.json" with the content previously indicated by you within this program, as shown in the image.<img src="//cdck-file-uploads-global.s3.dualstack.us-west-2.amazonaws.com/standard17/uploads/mbed/original/1X/2f87453ea2b64d0d27b7e9613fdae98f86364041.png" width="472" height="181" style="font-family: inherit;">
Would the file be created there or would it be somewhere else?
Finally I would like to thank your answers.
Good again, I have another question: I have run the serial terminal and I get the same as in your image of “Read: 0.060000” with baud rate 9600, but I get the same connecting it to the PA_3 pin that is not connected to any pin , I do not know if that’s normal, that is, I always get “Read: 0.060000”. Thank you!!
I just wanted to let you know that the “Nucleo_pwm” program uses an old version of Mbed OS, to get the most recent version of Mbed OS 5 I would recommend importing this PWM example program and copying/pasting your existing code from above into main.cpp: https://os.mbed.com/docs/latest/reference/pwmout.html#pwmout-hello-world
Also, I am able to read a different value from the PwmOut by adding a printf statement to the else condition in your while loop:
#include "mbed.h"
PwmOut servo(PA_3);
Serial my_serial(PC_6, PA_12);
int main() {
servo.period_us(20000);
int servopulsewidth = 1500;
int pata_si = 1200;
int pata_no = 1900;
bool mov = false;
servo.pulsewidth_us(servopulsewidth);
while(1) {
if (mov == true) {
servo.pulsewidth_us(pata_si);
my_serial.printf("Pata si: %f\r\n", servo.read());
} else {
servo.pulsewidth_us(pata_no);
my_serial.printf("Pata no: %f\r\n", servo.read());
}
mov = !mov;
wait_ms(250);
}
}
Then I read the following output from the serial terminal:
Good again! I have already changed to the version of the indicated program, but I have made a change that is: change PwmOut servo (PA_3) by SoftPWM servo (PA_3) and in this case if I move the servo with the indicated PIN (PA_3), it is that with PwmOut servo (PA_3) did not go and with this change yes. I do not know what can be due. Doing it this way would not require the mbed_app.json.
I do not know if the used will work, anyway it has been executed and the same as its capture.
