doc(sdio_slave): add descriptions about conflicts on MTDI pin
This commit is contained in:
michael
parent
9b1f2df900
commit
85b08684e3
153
docs/en/api-reference/peripherals/sd_pullup_requirements.rst
Normal file
153
docs/en/api-reference/peripherals/sd_pullup_requirements.rst
Normal file
|
|
@ -0,0 +1,153 @@
|
|||
SD Pullup Requirements
|
||||
======================
|
||||
|
||||
CMD and DATA lines D0-D3 of the slave should be pulled up by 50KOhm resistor
|
||||
even in 1-bit mode or SPI mode. The pullups of the slave cards should be
|
||||
connected even if they're not connected to the host.
|
||||
|
||||
The MTDI strapping pin is incompatible with DAT2 line pull-up by default
|
||||
when the code flash is 3.3V. See :ref:`mtdi_strapping_pin` below.
|
||||
|
||||
Pullup inside Official Modules
|
||||
------------------------------
|
||||
|
||||
For Espressif official modules, different weak pullups / pulldowns are
|
||||
connected to CMD, and DATA pins as below. To use these modules,
|
||||
these pins are required to be pulled up by 50KOhm resistors, since internal
|
||||
weak pullups are insufficient.
|
||||
|
||||
+-----------------------+-----+--------------------------+------+----------------------+------+
|
||||
| GPIO | 15 | 2 | 4 | 12 | 13 |
|
||||
+=======================+=====+==========================+======+======================+======+
|
||||
| Name | CMD | DAT0 | DAT1 | DAT2 | DAT3 |
|
||||
+-----------------------+-----+--------------------------+------+----------------------+------+
|
||||
| At startup | WPU | WPD | WPD | PU for 1.8v flash; | WPU |
|
||||
| | | | | WPD for 3.3v flash | |
|
||||
+-----------------------+-----+--------------------------+------+----------------------+------+
|
||||
| Strapping requirement | | Low to download to flash | | High for 1.8v flash; | |
|
||||
| | | | | Low for 3.3v flash | |
|
||||
+-----------------------+-----+--------------------------+------+----------------------+------+
|
||||
|
||||
- WPU: Weak pullup
|
||||
- WPD: Weak pulldown
|
||||
- PU: Pullup inside the module
|
||||
|
||||
For Wrover modules, they use 1.8v flash, and have pullup on GPIO12 inside.
|
||||
For Wroom-32 Series, PICO-D4 modules, they use 3.3v flash, and is weakly
|
||||
pulled down internally. See :ref:`mtdi_strapping_pin` below.
|
||||
|
||||
Pullup on Official Devkit (WroverKit)
|
||||
--------------------------------------
|
||||
|
||||
For official Wrover Kit (till version 3), some of the pullups are provided on
|
||||
the board as the table below. For other devkits that don't have pullups,
|
||||
please connect them yourselves.
|
||||
|
||||
+-----------------------+-----+------+------+------+---------+
|
||||
| GPIO | 15 | 2 | 4 | 12 | 13 |
|
||||
+=======================+=====+======+======+======+=========+
|
||||
| Name | CMD | DAT0 | DAT1 | DAT2 | DAT3 |
|
||||
+-----------------------+-----+------+------+------+---------+
|
||||
| Pullup on the Kit | PU | PU | PU | | PU & PD |
|
||||
+-----------------------+-----+------+------+------+---------+
|
||||
|
||||
- PU: Pullup
|
||||
- PD: Pulldown
|
||||
|
||||
The DAT3 pullup conflicts with JTAG pulldown in WroverKit v3 and earlier, please
|
||||
either:
|
||||
|
||||
1. pull it up by resistor less than 5KOhm (2kOhm suggested) in 4-bit mode.
|
||||
2. pull it up or drive it high by host or VDD3.3V in 1-bit mode.
|
||||
|
||||
.. _mtdi_strapping_pin:
|
||||
|
||||
MTDI strapping pin
|
||||
------------------
|
||||
|
||||
MTDI (GPIO12) is used as a bootstrapping pin to select output voltage of an
|
||||
internal regulator which powers the flash chip (VDD_SDIO). This pin has an
|
||||
internal pulldown so if left unconnected it will read low at reset (selecting
|
||||
default 3.3V operation). When adding a pullup to this pin for SD card
|
||||
operation, consider the following:
|
||||
|
||||
- For boards which don't use the internal regulator (VDD_SDIO) to power the
|
||||
flash, GPIO12 can be pulled high.
|
||||
- For boards which use 1.8V flash chip, GPIO12 needs to be pulled high at
|
||||
reset. This is fully compatible with SD card operation.
|
||||
- On boards which use the internal regulator and a 3.3V flash chip, GPIO12
|
||||
must be low at reset. This is incompatible with SD card operation. Please
|
||||
check the table below to see whether your modules/kits use 3.3v flash.
|
||||
|
||||
+-----------------+---------------+--------------------------------------+
|
||||
| Module | Flash voltage | DAT2 connections |
|
||||
+=================+===============+======================================+
|
||||
| PICO-D4 | 3.3V | Internal PD, change EFUSE and pullup |
|
||||
+-----------------+ + or disable DAT2 line* +
|
||||
| Wroom-32 Series | | |
|
||||
+-----------------+---------------+--------------------------------------+
|
||||
| Wrover | 1.8V | Internal PU, pullup suggested |
|
||||
+-----------------+---------------+--------------------------------------+
|
||||
|
||||
Official devkits of different types and version mount different types of
|
||||
modules, please refer to the table below to see whether your devkit can
|
||||
support SDIO slave without steps above.
|
||||
|
||||
+--------------------------+-----------------+---------------+
|
||||
| Devkit | Module | Flash voltage |
|
||||
+==========================+=================+===============+
|
||||
| PICO Kit | PICO-D4 | 3.3V |
|
||||
+--------------------------+-----------------+ (see steps +
|
||||
| DevKitC | Wroom-32 Series | below) |
|
||||
+--------------------------+ + +
|
||||
| WroverKit v2 and earlier | | |
|
||||
+--------------------------+-----------------+---------------+
|
||||
| WroverKit v3 | Wrover | 1.8V |
|
||||
+--------------------------+-----------------+---------------+
|
||||
|
||||
If your board requires internal regulator with 3.3v output, to make it
|
||||
compatible with SD pullup, you can either:
|
||||
|
||||
- **In the case using ESP32 host only**, external pullup can be omitted and an
|
||||
internal pullup can be enabled using a ``gpio_pullup_en(GPIO_NUM_12);`` call.
|
||||
Most SD cards work fine when an internal pullup on GPIO12 line is enabled.
|
||||
Note that if ESP32 experiences a power-on reset while the SD card is
|
||||
sending data, high level on GPIO12 can be latched into the bootstrapping
|
||||
register, and ESP32 will enter a boot loop until external reset with
|
||||
correct GPIO12 level is applied.
|
||||
- **In the case using ESP32 slave in 1-bit mode**, speicfy
|
||||
``SDIO_SLAVE_FLAG_DAT2_DISABLED`` in the slave to avoid slave detecting on
|
||||
DAT2 line. Note the host will not know 4-bit mode is not supported any more
|
||||
by the standard CCCR register. You have to tell the host use 1-bit only.
|
||||
- **For ESP32 host or slave**, another option is to burn the flash voltage
|
||||
selection efuses. This will permanently select 3.3V output voltage for the
|
||||
internal regulator, and GPIO12 will not be used as a bootstrapping pin.
|
||||
Then it is safe to connect a pullup resistor to GPIO12. This option is
|
||||
suggested for production use. NOTE this cannot be reverted once the EFUSE
|
||||
is burnt.
|
||||
|
||||
The following command can be used to program flash voltage selection efuses **to 3.3V**:
|
||||
|
||||
components/esptool_py/esptool/espefuse.py set_flash_voltage 3.3V
|
||||
|
||||
This command will burn the `XPD_SDIO_TIEH`, `XPD_SDIO_FORCE`, and
|
||||
`XPD_SDIO_REG` efuses. With all three burned to value 1, the internal
|
||||
VDD_SDIO flash voltage regulator is permanently enabled at 3.3V. See
|
||||
the technical reference manual for more details.
|
||||
|
||||
`espefuse.py` has a `--do-not-confirm` option if running from an automated flashing script.
|
||||
|
||||
GPIO2 Strapping pin
|
||||
-------------------
|
||||
|
||||
GPIO2 pin is used as a bootstrapping pin, and should be low to enter UART
|
||||
download mode. You may find it unable to enter the UART download mode if you
|
||||
correctly connect the pullup of SD on GPIO2. For WroverKit v3, there are
|
||||
dedicated circuits to pulldown the GPIO2 when downloading. For other boards,
|
||||
one way to do this is to connect GPIO0 and GPIO2 using a jumper, and then the
|
||||
auto-reset circuit on most development boards will pull GPIO2 low along with
|
||||
GPIO0, when entering download mode.
|
||||
|
||||
- Some boards have pulldown and/or LED on GPIO2. LED is usually ok, but
|
||||
pulldown will interfere with D0 signals and must be removed. Check the
|
||||
schematic of your development board for anything connected to GPIO2.
|
||||
|
|
@ -4,9 +4,6 @@ SDIO Card Slave Driver
|
|||
Overview
|
||||
--------
|
||||
|
||||
.. note:: At the moment, this code has been proven to work on the Wrover-Kit V3. Earlier versions of the Wrover-Kit
|
||||
and other development kits are electrically incompatible with this code. Functionality on other devboards is untested.
|
||||
|
||||
The ESP32 SDIO Card peripherals (Host, Slave) shares two sets of pins as below table.
|
||||
The first set is usually occupied by SPI0 bus which is responsible for the SPI flash holding the code to run.
|
||||
This means SDIO slave driver can only runs on the second set of pins while SDIO host is not using it.
|
||||
|
|
@ -29,15 +26,33 @@ This means SDIO slave driver can only runs on the second set of pins while SDIO
|
|||
| DAT3 | 10 | 13 |
|
||||
+----------+-------+-------+
|
||||
|
||||
The SDIO slave can run under 3 modes: SPI, 1-bit SD and 4-bit SD modes, which is detected automatically by the
|
||||
hardware. According to the SDIO specification, the host initialize the slave into SD mode by first sending CMD0 with
|
||||
DAT3 pin high, while initialize the slave into SPI mode by sending CMD0 with CS pin (the same pin as DAT3) low. After the
|
||||
initialization, the host can enable the 4-bit SD mode by writing CCCR register 0x07 by CMD52. All the bus detection
|
||||
process are handled by the slave peripheral.
|
||||
The SDIO slave can run under 3 modes: SPI, 1-bit SD and 4-bit SD modes, which
|
||||
is detected automatically by the hardware. According to the SDIO
|
||||
specification, CMD and DAT0-3 lines should be pulled up no matter in 1-bit,
|
||||
4-bit or SPI mode. Then the host initialize the slave into SD mode by first
|
||||
sending CMD0 with DAT3 pin high, while initialize the slave into SPI mode by
|
||||
sending CMD0 with CS pin (the same pin as DAT3) low.
|
||||
|
||||
The host has to communicate with the slave by an ESP-slave-specific protocol. The slave driver offers 3 services over
|
||||
Function 1 access by CMD52 and CMD53: (1) a sending FIFO and a receiving FIFO, (2) 52 8-bit R/W registers shared by
|
||||
host and slave, (3) 16 interrupt sources (8 from host to slave, and 8 from slave to host).
|
||||
.. note:: CMD and DATA lines D0-D3 of the card should be pulled up by 50KOhm resistor
|
||||
even in 1-bit mode or SPI mode. Most official devkits don't meet the pullup
|
||||
requirements by default, and there are conflicts on strapping pins as well.
|
||||
Please refer to :doc:`sd_pullup_requirements` to see how to setup your
|
||||
system correctly.
|
||||
|
||||
.. toctree::
|
||||
:hidden:
|
||||
|
||||
sd_pullup_requirements
|
||||
|
||||
After the initialization, the host can enable the 4-bit SD mode by writing
|
||||
CCCR register 0x07 by CMD52. All the bus detection process are handled by the
|
||||
slave peripheral.
|
||||
|
||||
The host has to communicate with the slave by an ESP-slave-specific protocol.
|
||||
The slave driver offers 3 services over Function 1 access by CMD52 and CMD53:
|
||||
(1) a sending FIFO and a receiving FIFO, (2) 52 8-bit R/W registers shared by
|
||||
host and slave, (3) 16 interrupt sources (8 from host to slave, and 8 from
|
||||
slave to host).
|
||||
|
||||
Terminology
|
||||
^^^^^^^^^^^
|
||||
|
|
@ -215,6 +230,7 @@ There are several ways to use the ``arg`` in the queue parameter:
|
|||
|
||||
More about this, see :example:`peripherals/sdio`.
|
||||
|
||||
|
||||
Application Example
|
||||
-------------------
|
||||
|
||||
|
|
|
|||
|
|
@ -60,6 +60,8 @@ See :doc:`SD/SDIO/MMC Driver <../storage/sdmmc>` for the higher level driver whi
|
|||
|
||||
See :doc:`SD SPI Host Driver <sdspi_host>` for a similar driver which uses SPI controller and is limited to SPI mode of SD protocol.
|
||||
|
||||
See :doc:`sd_pullup_requirements` for pullup support and compatiblities about modules and devkits.
|
||||
|
||||
API Reference
|
||||
-------------
|
||||
|
||||
|
|
|
|||
|
|
@ -0,0 +1 @@
|
|||
.. include:: ../../../en/api-reference/peripherals/sd_pullup_requirements.rst
|
||||
Loading…
Reference in a new issue