USB CDC on Nucleo 476RG

[ghost]

Hi,

Thanks for this awesome core! It makes it so much easier to program those STM32L4 chips...

I am trying to add a CDC UART on a Nucleo 476 board, with a micro USB adapter on pins PA9/PA11/PA12. This setup is programmed as a Dragonfly variant, via the onboard ST-Link.

When plugged through its USB CDC port, the board is correctly recognized by Windows, and I can connect to it with a terminal application on the computer. It receives the strings sent via the serial terminal on the PC, but an exception is raised on the microcontroller when it tries to send some data to the PC, and the data never makes it to the terminal application.

Any clue as to what might be going on? Is the USB CDC code only compatible with the Dragonfly's L476RE, and not the Nucleo's L476RG chip? Thanks,

Armel

[GrumpyOldPizza]

That actually should work. You should be able to do that without PA9, by using this define in variant.h:

define STM32L4_CONFIG_USB_VBUS GPIO_PIN_NONE

I'd not recommend using the "Dragonfly" entry for that. Just add #define USBCON to variant.h (and the upper define), and modify boards.txt to include the USB settings for the Nucleo board. "Dragonfly" uses different clocking internally.

Mind trying the simple example called "Asciitable", so that we are on the same page ?

• Thomas

On Fri, Feb 24, 2017 at 7:38 AM, TTrml notifications@github.com wrote:

Hi,

Thanks for this awesome core! It makes it so much easier to program those STM32L4 chips...

I am trying to add a CDC UART on a Nucleo 476 board, with a micro USB adapter on pins PA9/PA11/PA12. This setup is programmed as a Dragonfly variant, via the onboard ST-Link.

When plugged through its USB CDC port, the board is correctly recognized by Windows, and I can connect to it with a terminal application on the computer. It receives the strings sent via the serial terminal on the PC, but an exception is raised on the microcontroller when it tries to send some data to the PC, and the data never makes it to the terminal application.

Any clue as to what might be going on? Is the USB CDC code only compatible with the Dragonfly's L476RE, and not the Nucleo's L476RG chip? Thanks,

Armel

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[ghost]

Thanks Thomas for the quick response!

I followed your advice and got the "Asciitable" example to work... but surprisingly enough, if I take away the content of the loop() function, then the part printed in setup() doesn't show up, even though it is displayed when the content of loop() is kept!

Here is the code that doesn't print anything, even though the "Asciitable" example does: void setup() { //Initialize serial and wait for port to open: Serial.begin(9600); while (!Serial) { ; // wait for serial port to connect. Needed for native USB port only } // prints title with ending line break Serial.println("ASCII Table ~ Character Map"); } void loop() { }

[GrumpyOldPizza]

Excellent feedback. Is this with the latest code off github ? Or a downloaded release via json file ?

• Thomas

On Fri, Feb 24, 2017 at 10:53 AM, TTrml notifications@github.com wrote:

Thanks Thomas for the quick response!

I followed your advice and got the "Asciitable" example to work... but surprisingly enough, if I take away the content of the loop() function, then the part printed in setup() doesn't show up, even though it is displayed when the content of loop() is kept! Here is the code that doesn't print anything, even though the "Asciitable" example does: void setup() { //Initialize serial and wait for port to open: Serial.begin(9600); while (!Serial) { ; // wait for serial port to connect. Needed for native USB port only } // prints title with ending line break Serial.println("ASCII Table ~ Character Map"); } void loop() { }

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[ghost]

The code is from Github as of 3 days ago, and the same happens with the current code.

[ghost]

Ah just got it now! Text is only displayed if it exceeds a certain length - for instance, the previous example works if "ASCII Table ~ Character Map" is replaced with "ASCII Table ~ Charapppppppppppppppppppppppppppppppppppppppppcter Map", in which case the whole lot is shown

[GrumpyOldPizza]

Yup. There is a mechanism to avoid sending too small USB/CDC packets. I changed the code yesterday to use USB SOF callbacks over the previously SysTick based approach. So something is not flushing the packets. Thanx for investigating.

• Thomas

On Fri, Feb 24, 2017 at 11:34 AM, TTrml notifications@github.com wrote:

Ah just got it now! Text is only displayed if it exceeds a certain length - for instance, the previous example works if "ASCII Table ~ Character Map" is replaced with "ASCII Table ~ Charapppppppppppppppppppppppppppppppppppppppppcter Map", in which case the whole lot is shown

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[GrumpyOldPizza]

Fixed. STM32L433 always turned on SOF, STM32L476 needed a flag for that.

Is the crash still an issue ?

[ghost]

All good now, thanks a lot Thomas!