UART bootlader

[YDann.7]

Dear,

I'm using embedded STM32 UART bootloader to update the firmware of a slave STM32G070.

For some reasons, the host should maintain the slave in reset during a long time before starting slave bootloader.

Sometimes, when the slave is maintain in reset for a long time, the delay between the enable code from the host and the answer (ACK) from the slave takes greater time than espected.

In the Application note AN2606, the USART connection timing for a STM32G07xxx/08xxx expected is 0.16 ms for a communication at 115200 bauds. In my case, it takes around 20 ms.

Is it the typical timing ? And what can be the max timing for the USART connection ?

[TDK]

> In the Application note AN2606, the USART connection timing for a STM32G07xxx/08xxx expected is 0.16 ms for a communication at 115200 bauds.

Where are you seeing that? I don't see any guarantee on the time it takes for the chip to respond.

AN3155 is specific to the UART bootloader, but I don't see any guarantee in there either.

[YDann.7]

On page 279, there is the "Bootloader Startup timing" and on page 282, there is the "USART connection timing".

In table 122, you can see the USART bootloader minimum timing

It's no specify to be for a communication at 115200 bauds but I deduce it from the time of 1 USART byte.

I agree, there is any guarantee on the timing but I based my timeout for the response on the value of this table. I can increase this delay (and I do will do it).

The AN3155 describes only the USART protocol used by the STM32 bootlader without any timing diagram.

The AN2606 is more generic and talking about the STM32 bootloader.