Panicked at examples/uart_loopback_test.rs

[blietaer]

Dear SAM Team,

I am afraid the UART examples are not working out of the box on the SAM V71 Xultra (blue) Board anymore (? I can't confirm it ever did, first time I try it).
Maybe I am doing something wrong, or oversight of a minimum (undocumented) wiring here ?

Sounds like a Clock issue as we can easily track this error msg down to uart.rs:358 (might want to try and play with both MCK and PCK values).

I have the (exact) same situation for both the examples/uart_loopback_test.rs and the examples/uart_interrupts, while both examples/usart_loopback.rs (using a small wiring PB00-PB01 on J505) and examples/usb_serial_echo.rs (using second 9target) USB port) are working just fine.

Any hint/correction/suggestion is welcome here ! :)

Cheers,
Ben

[michalfita]

@blietaer for clarity as you haven't mentioned: Is it on released version (which one?) or from top of development branch?

Have you changed anything in the example code anywhere else?

Maybe @martinmortsell would have a quick hint for you?

[martinmortsell]

I think what happened is that there was a refactor of the clock API done after the uart examples where written, which caused the examples to break and this was never checked.

The problem is that there's a requirement that mck needs to be at least 3 times bigger than pck, and this is not fulfilled as the prescaler value is set to 1. Changing the HccPrescaler should fix this issue.

[blietaer]

Wow many thanks to both of you for this super quick feedback.

@blietaer for clarity as you haven't mentioned: Is it on released version (which one?) or from top of development branch?

Ah yes, this is development branch, sorry.

Have you changed anything in the example code anywhere else?

No no, this is a vanilla clone from repo.

The problem is that there's a requirement that mck needs to be at least 3 times bigger than pck, and this is not fulfilled as the prescaler value is set to 1. Changing the HccPrescaler should fix this issue.

Yes, this is my understanding just reviewing uart.rs: mmmh let me check if I can play with HccPrescaler directly from the example code, without touching anything under the HAL/PAC hood.

[blietaer]

Changing the pres value (second parameter of configure() ) from 1 to 3 seems indeed to fix this:

[michalfita]

@blietaer PR this change, please.

[blietaer]

Will do, but actually I was a bit quick: this only solves the example\uart_interrupts.rs but not the example\uart_loopback_test: I can't have anything printed (and I wired the same) not sure if my modification is suspicious here...can't hardly debug it :/
Trying different Tx/Rx pin (loop-wired too..), but not joy...