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CDC abnormal behaviour on STM32F767ZI - CDC Transimission broken after reset

Andrea Dall'Era
Associate II

My system -> Pc with WIN7 + STMF767ZI demo board + Putty for recive/transmitt data​.

In File.zip you can find the program that i write using CubeMX + Atollic 9.2.0.

q1) When i reset the board by clicking on reset button on the board, only the communication on UART3 staying alive why?

Reading some post on internet, i found one that tell:

When the device disconnects, PC application should close the COM port handle immediately, before the device re-connects. After the device connects, the app opens the COM port again. That is, the PC app has to monitor device disconnection / connection.

Unfortunately, the major terminal apps, like TeraTerm, PuTTY, br@y++, RealTerm, don’t take care of this "feature"

q2) If is it true? -> so if i write my own application to send/receive the data, i resolve the trouble ? I think after the connection is broken down by the reset i have to rebuilt the connection in my program by monitor the active connection, for example by using LIBUSB(Is the first time that i operate with com-protocol & uC - i'm a student on Electronics); or i have to integrate my code even in uC file? If is true what i miss or what i have to do?

q3) To avoid that the board start to transmit before mine application is connected is it the right/best way to test the channel if is it right open, like sending a test message ("TEST CDC COM")and wait the response ("CDC COM OK") -> Is it present in HAL a call back that inform the user if the connection is broken down or not active? or inform the user, that after a time, the transmissione isn't reach the goal, or i have to start a timer an after this is elapsed test the state of the connection (for example CDC_BUSY where i can find it?), or i think i have ro read a value of a register (that the transimssion is in progress or the peripheric is busy), which?

Please answer as well only a question (q1or q2 or q3), if it better that have rewrite q3 in an othet post, tell me, thank you.

1 REPLY 1
Andrea Dall'Era
Associate II

​P.S.: i have read only at once this documents: UM1734 Rev.4 + UM1720 DocID025799 Rev 3.

q4) Where i can find more informations?