From 65b01e5ab1b51c5ae82466fc9d02f5aa496730f3 Mon Sep 17 00:00:00 2001 From: Cai Xin Ying Date: Wed, 27 Sep 2023 06:35:53 +0800 Subject: [PATCH] docs: provide CN translation for api-reference/peripherals/sdspi_share.rst --- .../api-reference/peripherals/sdspi_share.rst | 62 ++++++++------- .../api-reference/peripherals/sdspi_share.rst | 77 ++++++++++++++++++- 2 files changed, 110 insertions(+), 29 deletions(-) diff --git a/docs/en/api-reference/peripherals/sdspi_share.rst b/docs/en/api-reference/peripherals/sdspi_share.rst index 5b8d0c2d40..ea178813b7 100644 --- a/docs/en/api-reference/peripherals/sdspi_share.rst +++ b/docs/en/api-reference/peripherals/sdspi_share.rst @@ -1,70 +1,76 @@ -Sharing the SPI bus among SD card and other SPI devices -======================================================= +Sharing the SPI Bus Among SD Cards and Other SPI Devices +======================================================== -The SD card has a SPI mode, which allows it to be communicated to as a SPI device. But there are some restrictions that we need to pay attention to. +:link_to_translation:`zh_CN:[中文]` -Pin loading of other devices +The SD card has an SPI mode, enabling it to function as an SPI device, but there are some restrictions that we need to pay attention to. + +Pin Loading of Other Devices ---------------------------- When adding more devices onto the same bus, the overall pin loading increases. The loading consists of AC loading (pin capacitor) and DC loading (pull-ups). -AC loading +AC Loading ^^^^^^^^^^ -SD cards, which are designed for high-speed communications, have small pin capacitors (AC loading) to work until 50MHz. However, the other attached devices will increase the pin's AC loading. +SD cards, designed for high-speed communications, have small pin capacitors (AC loading) to work until 50 MHz. However, the other attached devices will increase the pin's AC loading. -Heavy AC loading of a pin may prevent the pin from being toggled quickly. By using an oscilloscope, you will see the edges of the pin become smoother and not ideal any more (the gradient of the edge is smaller). The setup timing requirements of an SD card may be violoated when the card is connected to such bus. Even worse, the clock from the host may not be recognized by the SD card and other SPI devices on the same bus. +Heavy AC loading of a pin may prevent the pin from being toggled quickly. By using an oscilloscope, you will see the edges of the pin become smoother, i.e., the gradient of the edge is smaller. The setup timing requirements of an SD card may be violated when the card is connected to a bus with a high AC load. Even worse, high AC loads may cause the SD card and other SPI devices to fail to properly resolve clock signals from the host, affecting communication stability. -This issue may be more obvious if other attached devices are not designed to work at the same frequency as the SD card, because they may have larger pin capacitors. +This issue may be more obvious if other attached devices are not designed to work at the same frequency as the SD card, because they may have larger pin capacitors. The larger the pin capacity, the greater the pin response time, the smaller the max frequency the SD bus can work. To see if your pin AC loading is too heavy, you can try the following tests: -(Terminology: **launch edge**: at which clock edge the data start to toggle; **latch edge**: at which clock edge the data is supposed to be sampled by the receiver, for SD cad, it's the rising edge.) +Terminology: -1. Use an oscilloscope to see the clock and compare the data line to the clock. - - If you see the clock is not fast enough (for example, the rising/falling edge is longer than 1/4 of the clock cycle), it means the clock is skewed too much. + - **launch edge**: at which clock edge the data starts to toggle; + - **latch edge**: at which clock edge the data is supposed to be sampled by the receiver. For SD card, it is the rising edge. + +1. Use an oscilloscope to see the clock and compare the data line to the clock. + + - If you see the clock is not fast enough, e.g., the rising/falling edge is longer than 1/4 of the clock cycle, it means the clock is skewed too much. - If you see the data line unstable before the latch edge of the clock, it means the load of the data line is too large. - You may also observed the corresponding phenomenon (data delayed largely from launching edge of clock) with logic analyzers. But it's not as obvious as with an oscilloscope. + You may also observe the corresponding phenomenon that data delayed largely from the launching edge of the clock with logic analyzers. But it is not as obvious as with an oscilloscope. -2. Try to use slower clock frequency. +2. Try to use a slower clock frequency. - If the lower frequency can work while the higher frequency can't, it's an indication of the AC loading on the pins is too large. + If the lower frequency can work while the higher frequency cannot, it is an indication that the AC loading on the pins is too large. -If the AC loading of the pins is too large, you can either use other faster devices (with lower pin load) or slow down the clock speed. +If the AC loading of the pins is too large, you can either use other faster devices with lower pin load or slow down the clock speed. -DC loading +DC Loading ^^^^^^^^^^ -The pull-ups required by SD cards are usually around 10 kOhm to 50 kOhm, which may be too strong for some other SPI devices. +The pull-ups required by SD cards are usually around 10 kOhm to 50 kOhm, which may be too strong for some other SPI devices. -Check the specification of your device about its DC output current , it should be larger than 700uA, otherwise the device output may not be read correctly. +Check the specification of your device about its DC output current, it should be larger than 700 μA, otherwise, the device output may not be read correctly. -Initialization sequence +Initialization Sequence ----------------------- .. note:: - If you see any problem in the following steps, please make sure the timing is correct first. You can try to slow down the clock speed (SDMMC_FREQ_PROBING = 400 KHz for SD card) to avoid the influence of pin AC loading (see above section). + If you see any problem in the following steps, please make sure the timing is correct first. You can try to slow down the clock speed, such as setting ``SDMMC_FREQ_PROBING`` to 400 kHz for SD card, to avoid the influence of pin AC loading, as discussed in the previous section. -When using ab SD card with other SPI devices on the same SPI bus, due to the restrictions of the SD card startup flow, the following initialization sequence should be followed: (See also :example:`storage/sd_card`) +When using an SD card with other SPI devices on the same SPI bus, due to the restrictions of the SD card startup flow, the following initialization sequence should be followed. Refer to :example:`storage/sd_card` for further details. -1. Initialize the SPI bus properly by `spi_bus_initialize`. +1. Initialize the SPI bus properly by :cpp:func:`spi_bus_initialize`. -2. Tie the CS lines of all other devices than the SD card to high. This is to avoid conflicts to the SD card in the following step. +2. Tie the CS lines of all other devices than the SD card to idle state (by default it's high). This is to avoid conflicts with the SD card in the following step. You can do this by either: - 1. Attach devices to the SPI bus by calling `spi_bus_add_device`. This function will initialize the GPIO that is used as CS to the idle level: high. + 1. Attach devices to the SPI bus by calling :cpp:func:`spi_bus_add_device`. This function will by default initialize the GPIO that is used as CS to the idle level: high. 2. Initialize GPIO on the CS pin that needs to be tied up before actually adding a new device. - 3. Rely on the internal/external pull-up (not recommended) to pull-up all the CS pins when the GPIOs of ESP are not initialized yet. You need to check carefull the pull-up is strong enough and there are no other pull-downs that will influence the pull-up (For example, internal pull-down should be enabled). + 3. Rely on the internal/external pull-up (**not recommended**) to pull up all the CS pins when the GPIOs of ESP are not initialized yet. You need to check carefully the pull-up is strong enough and there are no other pull-downs that will influence the pull-up. For example, internal pull-down should be enabled. -3. Mount the card to the filesystem by calling `esp_vfs_fat_sdspi_mount`. +3. Mount the card to the filesystem by calling :cpp:func:`esp_vfs_fat_sdspi_mount`. - This step will put the SD card into the SPI mode, which SHOULD be done before all other SPI communications on the same bus. Otherwise the card will stay in the SD mode, in which mode it may randomly respond to any SPI communications on the bus, even when its CS line is not addressed. + This step will put the SD card into the SPI mode, which **should** be done before all other SPI communications on the same bus. Otherwise, the card will stay in the SD mode, in which mode it may randomly respond to any SPI communications on the bus, even when its CS line is not addressed. - If you want to test this behavior, please also note that, once the card is put into SPI mode, it will not return to SD mode before next power cycle, i.e. powered down and powered up again. + If you want to test this behavior, please also note that, once the card is put into SPI mode, it will not return to SD mode before the next power cycle, i.e., powered down and powered up again. 4. Now you can talk to other SPI devices freely! diff --git a/docs/zh_CN/api-reference/peripherals/sdspi_share.rst b/docs/zh_CN/api-reference/peripherals/sdspi_share.rst index 9c7b44f913..6dd2fc433a 100644 --- a/docs/zh_CN/api-reference/peripherals/sdspi_share.rst +++ b/docs/zh_CN/api-reference/peripherals/sdspi_share.rst @@ -1 +1,76 @@ -.. include:: ../../../en/api-reference/peripherals/sdspi_share.rst +SD 卡与其他 SPI 设备共享 SPI 总线 +======================================================== + +:link_to_translation:`en:[English]` + +SD 卡支持 SPI 模式，使其能够作为 SPI 设备通信，但使用时需注意其限制。 + +其他设备的管脚负载 +---------------------------- + +向同一总线添加设备会增加管脚的整体负载，包括交流负载（管脚电容）和直流负载（上拉电阻）。 + +交流负载 +^^^^^^^^^^ + +在通信速率不超过 50 MHz 的情况下，专为高速通信设计的 SD 卡采用小型管脚电容（交流负载小）。但在同一 SPI 总线上连接其他设备后，会增加管脚的交流负载。 + +管脚交流负载过高时，可能无法实现电平快速切换。通过使用示波器，你可以观察到管脚状态变化的边缘变得更加平滑，即边缘变化率更低。当 SD 卡连接到交流负载较高的总线时，可能无法满足 SD 卡建立时间 (setup) 的时序要求。高交流负载甚至可能导致 SD 卡和其他 SPI 设备无法正确解析主机发出的时钟信号，影响通信稳定性。 + +如果连接的其他设备的工作频率与 SD 卡工作频率不同，上述问题可能会更加明显。这是因为其他设备可能具有更大的管脚电容。管脚容量越大，响应时间越长，SD 总线可工作的最高频率越低。 + +你可以尝试以下测试，判断管脚交流负载是否过重： + +术语 + + - **启动边沿 (launch edge)**：数据开始切换的时钟边沿； + - **锁存边沿 (latch edge)**：数据接收侧应进行数据采样的时钟边沿，对 SD 卡来说是上升沿。 + +1. 使用示波器观察时钟，并比较数据线与时钟。 + + - 如果时钟不够快，例如上升/下降沿长于时钟周期的 1/4，表明时钟偏斜过大。 + - 如果在时钟锁存边沿之前数据线不稳定，表明数据线负载过大。 + + 借助逻辑分析仪，也可以观察到数据与时钟启动沿相比，延迟较大。但比起用示波器，用逻辑分析仪观察到的现象可能不太明显。 + +2. 尝试使用较低的时钟频率。 + + 如果设备可以在较低的通信频率下正常工作，而在较高的通信频率下出现问题，说明管脚交流负载过大。 + +如果管脚的交流负载过大，你可以选择使用其他管脚负载更低但通信速度更快的设备，或降低时钟速度。 + +直流负载 +^^^^^^^^^^ + +SD 卡所需的上拉电阻通常在 10 kΩ 至 50 kΩ 之间，注意对某些 SPI 设备来说，这可能是过强的上拉电阻。 + +请查阅设备的规格说明书，了解其直流输出电流。此直流输出电流应大于 700 μA，否则可能无法正确读取设备输出。 + +初始化顺序 +----------------------- + +.. note:: + + 如果在执行以下步骤时遇到任何问题，请首先确保时序正确。如前文所述，你可以尝试降低时钟速度，例如将 SD 卡的 ``SDMMC_FREQ_PROBING`` 设置为 400 kHz，排除管脚交流负载的影响。 + +在同一 SPI 总线上与其他 SPI 设备一起使用 SD 卡时，由于 SD 卡启动流程的限制，应遵循以下初始化顺序。有关详情，请参阅 :example:`storage/sd_card`。 + +1. 通过 :cpp:func:`spi_bus_initialize` 正确初始化总线。 + +2. 将除 SD 卡外所有设备的 CS 线置为空闲状态（默认为高电平），避免在后续步骤中与 SD 卡发生冲突。 + + 这可以通过以下任一方式实现： + + 1. 调用 :cpp:func:`spi_bus_add_device` 将设备连接到 SPI 总线，该函数将初始化用作 CS 的 GPIO 管脚到空闲电平：默认为高电平。 + + 2. 在添加新设备前，初始化需要拉高的 CS 管脚 GPIO。 + + 3. 在 ESP 的 GPIO 未初始化前，依靠内部/外部上拉电阻拉高所有 CS 管脚（**不推荐**）。请确保上拉电阻拥有足够强度，且没有其他下拉电阻影响拉高。例如，应启用内部下拉电阻。 + +3. 调用 :cpp:func:`esp_vfs_fat_sdspi_mount` 将卡挂载到文件系统。 + + 此步骤将使 SD 卡进入 SPI 模式，**应该** 在同一总线上的所有其他 SPI 通信前完成。否则，SD 卡会保持在 SD 模式，即使在未选中其 CS 线的情况下，SD 卡也可能随机响应总线上的任何 SPI 通信。 + + 如果你想测试这种行为，请注意，一旦 SD 卡置于 SPI 模式，在下次上电前，也就是断电后重新上电之前，SD 卡将不会返回 SD 模式 + +4. 此时，即可与其他 SPI 设备自由通信。