268 lines
10 KiB
ReStructuredText
268 lines
10 KiB
ReStructuredText
SD Pullup Requirements
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======================
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CMD and DATA lines D0-D3 of the slave should be pulled up by 10 kOhm resistor
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even in 1-bit mode or SPI mode. The pullups of the slave cards should be
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connected even if they're not connected to the host.
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The MTDI strapping pin by default is incompatible with DAT2 line pullup when
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the flash is 3.3 V. See :ref:`technical_detail_sdio` below.
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.. _existing_issues_official_modules_sdio:
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Possible Issues
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---------------
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Here is a list of Espressif chips, official modules and development kits and
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the issues they may have during SDIO development. Since the requirements are
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for the pullups on the SD bus, the issues should be resolved no matter if it
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is a host or slave. Each issue is linked to its solution. The solution for a
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specific issue may be different for host and slave.
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Official modules are usually without the sufficient pullups on all 6 pins, it
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is suggested to select one of the development kits for either host or slave
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to provide such pullups.
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Chips
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^^^^^
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- ESP32 (except D2WD, see `ESP32 datasheet <https://www.espressif.com/sites/default/files/documentation/esp32_datasheet_en.pdf>`_):
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:ref:`sd_pullup_no_pullups`, whether the strapping conflicts with DAT2 is determined
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by the flash you are using. Please see :ref:`strapping_conflicts_dat2` if
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your flash chip is 3.3 V.
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- ESP32-D2WD:
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:ref:`sd_pullup_no_pullups`, :ref:`no_pullup_on_gpio12`
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- ESP32-PICO-D4:
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:ref:`sd_pullup_no_pullups`, :ref:`strapping_conflicts_dat2`
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Modules
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^^^^^^^
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- ESP32-WROOM-32 Series:
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Including ESP32-WROOM-32, ESP32-WROOM-32D, ESP32-WROOM-32U and
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ESP32-SOLO-1.
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:ref:`sd_pullup_no_pullups`, :ref:`strapping_conflicts_dat2`.
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- ESP32-WROVER Series:
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Including ESP32-WROVER and ESP32-WROVER-I.
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:ref:`sd_pullup_no_pullups`.
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- ESP32-WROVER-B Series:
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Including ESP32-WROVER-B and ESP32-WROVER-IB.
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:ref:`sd_pullup_no_pullups`, :ref:`strapping_conflicts_dat2`.
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.. _sdio_dev_kits:
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Development Boards
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^^^^^^^^^^^^^^^^^^
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- ESP32-PICO-KIT:
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Including PICO-KIT v4.1, v4.0 and v3.
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:ref:`sd_pullup_no_pullups`, :ref:`strapping_conflicts_dat2`,
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:ref:`gpio2_strapping_pin`.
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- ESP32-DevKitC:
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Including ESP32-DevKitC v4 and v2.
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:ref:`sd_pullup_no_pullups`, :ref:`strapping_conflicts_dat2`,
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:ref:`gpio2_strapping_pin`.
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- ESP-WROVER-KIT:
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v4.1: Have pullups, but :ref:`pullup_conflicts_on_gpio13` ,
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:ref:`strapping_conflicts_dat2`.
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v3: Have pullups, but :ref:`pullup_conflicts_on_gpio13`.
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v2 and v1: Have pullups, but :ref:`pullup_conflicts_on_gpio13`,
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:ref:`strapping_conflicts_dat2`, :ref:`gpio2_strapping_pin`.
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You can tell the version of your ESP23-WROVER-KIT version from the module
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on it: v4.1 are with ESP32-WROVER-B modules, v3 are with ESP32-WROVER
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modules, while v2 and v1 are with ESP32-WROOM-32 modules.
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- ESP32-LyraTD-MSC:
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:ref:`strapping_conflicts_dat2`. Have pullups.
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- ESP32-LyraT:
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Have pullups, but :ref:`pullup_conflicts_on_gpio13`
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Non-Espressif Hosts
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^^^^^^^^^^^^^^^^^^^
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Please make sure that your 3rd party SDIO host has correct pullups for all
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the signals.
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Solutions
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---------
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.. _sd_pullup_no_pullups:
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No Pullups
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^^^^^^^^^^
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When developing on boards without pullups, you can either:
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1. If your host and slave are on seperated boards, you can change one of them
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to a board with pullups. Please see :ref:`sdio_dev_kits` to find Espressif
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official boards with pullups.
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2. Connect external pullups to VDD by yourself. Connect these pins without
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pullups to the VDD through a 10 kOhm resistor.
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.. _pullup_conflicts_on_gpio13:
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Pullup Conflicts on GPIO13
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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The DAT3 of slave may not be properly pulled up. You can either:
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1. Use 1-bit mode, and tie DAT3 of slave to VDD.
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2. Use SPI mode.
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3. Remove the pulldown resistors on GPIO13; or pull it up by resistor less
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than 5 kOhm (2 kOhm suggested); or pull it up or drive it high by host or
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VDD3.3V in 1-bit mode.
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.. _strapping_conflicts_dat2:
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Conflicts Between Bootstrap and SDIO on DAT2
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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The strapping requirements conflict with SDIO protocol. See
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:ref:`mtdi_strapping_pin` for the details of this issue. You can either:
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1. (Recomended) Burn the flash voltage selection eFuses. This will
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permanently select 3.3 V output voltage for the internal regulator, and GPIO12
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will not be used as a bootstrapping pin. Then connect a pullup resistor
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to GPIO12.
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.. warning:: Burning eFuse is irreversible. The issue list above may be
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out of date. Do make sure the module you are burning is using a 3.3 V flash
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according to the information on http://www.espressif.com/. If you burn the
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3.3 V eFuses on an 1.8 V module, the module will get broken.
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Run the command below under your IDF folder:
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::
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components/esptool_py/esptool/espefuse.py set_flash_voltage 3.3V
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This command will burn the `XPD_SDIO_TIEH`, `XPD_SDIO_FORCE`, and
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`XPD_SDIO_REG` eFuses. With all three burned to value 1, the internal
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VDD_SDIO flash voltage regulator is permanently set to 3.3 V. You will
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see the following log if the burning succeeds:
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::
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espefuse.py v2.6
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Connecting....
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Enable internal flash voltage regulator (VDD_SDIO) to 3.3 V.
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The following eFuses are burned: XPD_SDIO_FORCE, XPD_SDIO_REG, XPD_SDIO_TIEH.
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This is an irreversible operation.
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Type 'BURN' (all capitals) to continue.
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BURN
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VDD_SDIO setting complete.
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You can also run ``components/esptool_py/esptool/espefuse.py summary`` to
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check the status of the eFuses above.
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`espefuse.py` has a ``--do-not-confirm`` option if running from an
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automated flashing script.
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See the ESP32 Technical Reference Manual for more details.
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2. **When using 1-bit mode or SPI mode**, DAT2 signal is not needed (though it
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still has to be pulled up). If the device works as the host, you can leave
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the DAT2 of host floating, and directly connect DAT2 of slave to VDD; or if
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the device works as the slave, specify ``SDIO_SLAVE_FLAG_DAT2_DISABLED`` in
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the slave app to avoid slave detecting on DAT2 line. Note the host will
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not know that 4-bit mode is not supported any more by the standard CCCR
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register. You have to forbid the host from using 4-bit mode.
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.. _no_pullup_on_gpio12:
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No Pullup on GPIO12
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^^^^^^^^^^^^^^^^^^^
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Your module is compatible with the SDIO protocol. Just connect GPIO12 to the
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VDD through a 10 kOhm resistor.
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.. _gpio2_strapping_pin:
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Auto-program Not Working (minor issue)
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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GPIO2 pin is used as a bootstrapping pin, and should be low to enter UART
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download mode. You may find it unable to enter the UART download mode if you
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correctly connect the pullup of SD on GPIO2.
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Some official kits pull down GPIO2 when downloading. For other boards, you
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may try to connect GPIO0 and GPIO2 using a jumper, and then the auto-reset
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circuit on most development boards will pull GPIO2 low along with GPIO0, when
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entering download mode. (Some boards have pulldown and/or LED on GPIO2. LED
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is usually ok, but the pulldown resistor will interfere with D0 signals and
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must be removed. Check the schematic of your development board for anything
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connected to GPIO2.)
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If the above way is not working, please just turn off the other device and
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remove the pullups on GPIO2 when you are programming the slave.
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.. _technical_detail_sdio:
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Technical Details
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-----------------
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.. _mtdi_strapping_pin:
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MTDI Strapping Pin
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^^^^^^^^^^^^^^^^^^
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MTDI (GPIO12) is used as a bootstrapping pin to select output voltage of an
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internal regulator which powers the flash chip (VDD_SDIO). This pin has an
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internal pulldown so if left unconnected it will read low at startup
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(selecting default 3.3 V operation).
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For ESP32-WROVER modules, excluding ESP32-WROVER-B, they use 1.8 V flash, and
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have pullup on GPIO12 inside. For other modules, which use 3.3 V flash, have
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no pullups on GPIO12, and GPIO12 is weakly pulled down internally.
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When adding a pullup to this pin for SD card operation, consider the
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following:
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- For boards which don't use the internal regulator (VDD_SDIO) to power the
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flash, GPIO12 can be pulled high.
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- For boards which use 1.8 V flash chip, GPIO12 needs to be pulled high at
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reset. This is fully compatible with SD card operation.
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- On boards which use the internal regulator and a 3.3 V flash chip, GPIO12
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must be low at reset. This is incompatible with SD card operation. Please
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check :ref:`existing_issues_official_modules_sdio` to see whether your board
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has this issue, and how to solve it.
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Internal Pullups and Strapping Requirements
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^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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It is never recommended to rely on internal weak pullups for SDIO
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communications, since internal weak pullups are insufficient. But information
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of the strapping requirements and internal pullups may be useful. For
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Espressif official modules, different weak pullups / pulldowns are connected
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to CMD, and DATA pins as below.
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+-----------------------+-----+--------------------------+------+-----------------------+------+
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| GPIO | 15 | 2 | 4 | 12 | 13 |
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+=======================+=====+==========================+======+=======================+======+
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| Name | CMD | DAT0 | DAT1 | DAT2 | DAT3 |
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+-----------------------+-----+--------------------------+------+-----------------------+------+
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| At startup | WPU | WPD | WPD | PU for 1.8 V flash; | WPU |
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| | | | | WPD for 3.3 V flash | |
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+-----------------------+-----+--------------------------+------+-----------------------+------+
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| Strapping requirement | | Low to download to flash | | High for 1.8 V flash; | |
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| | | | | Low for 3.3 V flash | |
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+-----------------------+-----+--------------------------+------+-----------------------+------+
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- WPU: Weak pullup
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- WPD: Weak pulldown
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- PU: Pullup inside the module |