kopia lustrzana https://github.com/espressif/esp-idf
116 wiersze
5.2 KiB
Markdown
116 wiersze
5.2 KiB
Markdown
### SDIO Example
|
|
|
|
## Introduction
|
|
|
|
These two projects illustrate the SDIO driver (host and slave). The host
|
|
example shows how to initialize a SDIO card, respond to a slave interrupt, as
|
|
well as reading and writing registers and buffers. The slave is a dedicated
|
|
peripheral, providing 8 interrupts, 52 8-bit R/W registers, an input FIFO and
|
|
an output FIFO. The example shows how to configure the driver and use these
|
|
feature.
|
|
|
|
The host first tell the slave to write the registers to a specified value,
|
|
then reads and prints the value from the slave. Then tell the slave to send 8
|
|
interrupts to the host. Then the host start sending data to the slave FIFO
|
|
and then reads from the slave FIFO in loops.
|
|
|
|
## Wiring
|
|
|
|
The SDIO protocol requires at least 4 lines (one more line than SD memory
|
|
protocol): CMD, CLK, DAT0 and DAT1. DAT1 is mandatory for the interrupt. DAT2
|
|
is required if 4-bit mode is used. DAT3 is required in 4-bit mode (connected
|
|
to host), or required by the slave as mode detect in 1-bit mode (pull up). It
|
|
is okay in 1-bit mode to leave DAT3 of host disconnected.
|
|
|
|
Please run wires between the slave and master to make the example function
|
|
(pins are the same for the host and the slave):
|
|
|
|
======== =========
|
|
Signal GPIO NUM
|
|
======== =========
|
|
CLK GPIO14
|
|
CMD GPIO15
|
|
DAT0 GPIO2
|
|
DAT1 GPIO4
|
|
DAT2 GPIO12
|
|
DAT3 GPIO13
|
|
Ground GND
|
|
======== =========
|
|
|
|
CMD and DAT0-3 lines require to be pulled up by 50KOhm resistors even in
|
|
1-bit mode. See *Board Compability* below for details. In 1-bit mode, the
|
|
host can make use of DAT2 and DAT3, however the slave should leave them alone
|
|
but pulled up.
|
|
|
|
Be aware that the example uses lines normally reserved for JTAG. If you're
|
|
using a board with JTAG functions, please remember to remove jumpers
|
|
connecting to the JTAG adapter. The SD peripheral works at a high frequency
|
|
and uses native pins, there's no way to configure it to other pins through
|
|
the GPIO matrix.
|
|
|
|
Please make sure CMD and DATA lines are pulled up by 50KOhm resistors even in
|
|
1-bit mode or SPI mode, which is required by the SD specification.
|
|
|
|
The 4-bit mode can be configured in the menuconfig. If the 4-bit mode is not
|
|
used, the host will not control the DAT3 line, the slave hardware is
|
|
responsible to pull-up the line (or the slave may run into the SPI mode and
|
|
cause a crash).
|
|
|
|
The host uses HS mode by default. If the example does not work properly,
|
|
please try connecting two boards by short wires, grounding between two boards
|
|
better or disabling the HS mode in menuconfig.
|
|
|
|
## Board compatibility
|
|
|
|
1. If you're using a board (e.g. WroverKit v2 and before, PICO, DevKitC)
|
|
which is not able to drive GPIO2 low on downloading, please remember to
|
|
disconnect GPIO2 between two boards when downloading the application.
|
|
|
|
2. It is suggested to use the official Wrover Kit as the slave. This is
|
|
because Wrover Kits have pullups on CMD, DAT0 and DAT1. Otherwise you'll have
|
|
to connect the pullups manually (or use the Wrover Kit as the host). However,
|
|
due to a PCB issue, Wrover Kits v3 and earlier have pullup v.s. pulldown
|
|
conflicts on DAT3 line. You'll have to:
|
|
|
|
1. Pull up GPIO13 by resistor of 5KOhm or smaller (2KOhm suggested)
|
|
in 4-bit mode.
|
|
2. Pull up, or tie GPIO13 to VDD3.3 in 1-bit mode.
|
|
|
|
To help you faster evaluate the SDIO example on devkits without pullups,
|
|
you can uncomment the pullup enable flags in the initialization code of
|
|
the app_main of host or slave. This enables internal weak pullups on CMD,
|
|
DAT0 and DAT1 and DAT3 lines. However please don't rely on internal weak
|
|
pullups in your own design.
|
|
|
|
3. Moreover, if your slave devkit is using code flash of 3.3V, it is required
|
|
to pull down DAT2 line to set proper flash voltage. This conflicts with SDIO
|
|
pullup requirements. Currently devkits using PICO-D4 and Wroom-32 series
|
|
modules have this problem. You can either:
|
|
|
|
- Use Wrover Kit v3 which integrates a Wrover module
|
|
- Still use PICO-D4 or Wroom-32 Series modules as the slave, however:
|
|
- Don't connect the DAT2 pin and leave it floating. This means
|
|
you have to use 1-bit mode in the host. ``SDIO_DAT2_DISABLED``
|
|
option should be enabled in the menuconfig to avoid using of
|
|
DAT2. Or:
|
|
- Burn the EFUSE to force the module using 3.3V as the flash
|
|
voltage. In this way the voltage of flash doesn't depend on MTDI
|
|
any more, connect DAT2 to the host and make sure it is pulled up
|
|
correctly. See document below.
|
|
|
|
See docs in the programming guide ``api_reference/peripherals/sdio_slave``
|
|
and ``api_reference/peripherals/sd_pullup_requirements`` to see more
|
|
descriptions about pullups and MTDI requirements and solutions of official
|
|
modules and devkits.
|
|
|
|
## About esp_slave component in this example
|
|
|
|
The component in this example shows how to communicate with esp32 sdio slave
|
|
correctly. However, currently it is for example purpose only.
|
|
|
|
The example shows how to talk with the slave, but doesn't show how to handle
|
|
exceptions. Assertion fails if any of the preconditions (connections,
|
|
grounding, slave data preparation, etc.) is not met.
|
|
|
|
Please do check and handle the return value in your real product.
|