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nRF Connect SDK Fundamentals : Lesson 5 Quizz : RTS question

MDev

I have problem with one question of the lesson 5 Quizz of the "nRF Connect SDK Fundamentals" course (Dev Academy)

https://academy.nordicsemi.com/courses/nrf-connect-sdk-fundamentals/lessons/lesson-4-serial-communication-uart/quizzes/lesson-5-quiz/

Here is the question :

Regarding the name, RTS is "request to send", so RTS indicate that the device is ready to receive and not to send, so the answer 2 seems not the good one.

RTS is used to indicate that the device is busy or not, and ready or not to accept new data. So answer 4 seems to be the closest one to what can be a good answer.

What do you think ?

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    Hi,

    Upon further scrutiny, it turns out the original text of the lesson was not technically wrong, although it did not paint the full picture either. Therefore, we consider it to have been slightly misleading.

    What typically happens, when using HWFC and Device A wants to send data to Device B, is the following:

    1. Device A sets its RTS active, to indicate that it wants to send
    2. Device B reads the active signal on its CTS, and prepares to receive
    3. Device B, once ready to receive, sets its RTS active
    4. Device A reads the active signal on its CTS, indicating it is allowed to send the data

    As such, it is technically true that a device, when it wants to send, "use its RTS to indicate that it is ready to send new data and read its CTS to see if it is allowed to send [the] data to the other end". However, the description is easily misunderstood, it does not give the full picture, and one might easily get confused.

    Still, for most intents and purposes the main mechanism is that of the receiving device setting RTS active when it is ready to receive, and the sending device sending only when reading an active signal on CTS. This is the mechanism at play once the transmission has started, where the receiver disables RTS whenever the buffers are full, and reenables RTS whenever the buffers are empty, signalling to the sender when it can send data. The course has been changed to reflect this. This is also how HWFC is explained in most of our Product Specifications and Datasheets.

    Regards,
    Terje

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  • 0

    Hi,

    Upon further scrutiny, it turns out the original text of the lesson was not technically wrong, although it did not paint the full picture either. Therefore, we consider it to have been slightly misleading.

    What typically happens, when using HWFC and Device A wants to send data to Device B, is the following:

    1. Device A sets its RTS active, to indicate that it wants to send
    2. Device B reads the active signal on its CTS, and prepares to receive
    3. Device B, once ready to receive, sets its RTS active
    4. Device A reads the active signal on its CTS, indicating it is allowed to send the data

    As such, it is technically true that a device, when it wants to send, "use its RTS to indicate that it is ready to send new data and read its CTS to see if it is allowed to send [the] data to the other end". However, the description is easily misunderstood, it does not give the full picture, and one might easily get confused.

    Still, for most intents and purposes the main mechanism is that of the receiving device setting RTS active when it is ready to receive, and the sending device sending only when reading an active signal on CTS. This is the mechanism at play once the transmission has started, where the receiver disables RTS whenever the buffers are full, and reenables RTS whenever the buffers are empty, signalling to the sender when it can send data. The course has been changed to reflect this. This is also how HWFC is explained in most of our Product Specifications and Datasheets.

    Regards,
    Terje

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