153 lines
8 KiB
ReStructuredText
153 lines
8 KiB
ReStructuredText
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.
|