SDIO Card Slave Driver
Overview
The ESP32 SDIO Card host and slave peripherals share two sets of pins, as shown in the table below. The first set is usually occupied by the SPI0 bus, which is responsible for the SPI flash holding the code to run. This means the SDIO slave driver can only run on the second set of pins while the SDIO host is not using it.
The SDIO slave can run under three modes: SPI, 1-bit SD, and 4-bit SD modes. Based on the signals on the interface, the device can determine the current mode and configure itself to adapt to that mode. Later, the slave driver can communicate with the slave device to properly handle commands and data transfers. According to the SDIO specification, the CMD and DAT0-3 signal lines should be pulled up whether in 1-bit SD, 4-bit SD or SPI mode.
Connections
Pin Name |
Corresponding Pins in SPI Mode |
GPIO Number (Slot 1) |
GPIO Number (Slot 2) |
---|---|---|---|
CLK |
SCLK |
6 |
14 |
CMD |
MOSI |
11 |
15 |
DAT0 |
MISO |
7 |
2 |
DAT1 |
Interrupt |
8 |
4 |
DAT2 |
N.C. (pullup) |
9 |
12 |
DAT3 |
#CS |
10 |
13 |
1-bit SD mode: Connect CLK, CMD, DAT0, DAT1 pins, and the ground.
4-bit SD mode: Connect all pins, and the ground.
SPI mode: Connect SCLK, MOSI, MISO, Interrupt, #CS pins, and the ground.
Note
Please check if CMD and DATA lines DAT0-DAT3 of the card are properly pulled up by 10 KOhm - 90 KOhm resistors, which should be ensured even in 1-bit mode or SPI mode. Most official modules do not offer these pullups internally. If you are using official development boards, check Overview of Compatibility to see whether your development boards have such pullups.
Note
Most official modules have conflicts on strapping pins with the SDIO slave function. If you are using an ESP32 module with 3.3 V flash inside, when you are developing on the module for the first time, you will need to perform an eFuse burn-in prior to development. This will adjust the pin configuration of the module to make the module compatible with SDIO functionality. See Overview of Compatibility for details on how to configure this.
Here is a list of modules/kits with 3.3 V flash:
Modules: All modules except ESP32-WROVER, ESP32-WROVER-I, ESP32-S3-WROOM-2, and please check Modules Overview for module list
Kits: ESP32-PICO-KIT, ESP32-DevKitC (up to v4), ESP32-WROVER-KIT (v4.1 [also known as ESP32-WROVER-KIT-VB], v2, v1 [also known as DevKitJ v1])
You can tell the version of your ESP23-WROVER-KIT version from the module on it: v4.1 are with ESP32-WROVER-B modules, v3 are with ESP32-WROVER modules, while v2 and v1 are with ESP32-WROOM-32 modules.
Refer to SD Pull-up Requirements for more technical details of the pullups.
The host initializes the slave into SD mode by sending the CMD0 command with the DAT3 pin set to a high level. Alternatively, the host initializes the SPI mode by sending CMD0 with CS pin low, which is the same pin as DAT3.
After the initialization, the host can enable the 4-bit SD mode by writing CCCR register 0x07 by CMD52. All the bus detection processes are handled by the slave peripheral.
The host has to communicate with the slave by an ESP-slave-specific protocol.
The slave driver offers three services over Function 1 access by CMD52 and CMD53:
sending and receiving FIFO
52 R/W registers (8-bit) shared by host and slave
16 interrupt sources (8 from host to slave, and 8 from slave to host)
Terminology
The SDIO slave driver uses the following terms:
A transfer is initiated by a command token from the host and may consist of a response and multiple data blocks. The core mechanism of the ESP32 SDIO slave driver involves data exchange and communication through transfers.
Sending: slave to host transfers.
Receiving: host to slave transfers.
Note
The register names in ESP32 Technical Reference Manual > SDIO Slave Controller [PDF] are organized from the host's perspective. For instance, RX
registers indicate sending, while TX
registers denote receiving. In our driver implementation, we've chosen not to utilize the terms TX
or RX
to prevent any potential ambiguities.
FIFO: A designated address within Function 1 that can be accessed using CMD53 commands for reading or writing substantial volumes of data. The address corresponds to the length intended for reading from or writing to the slave in a single transfer: requested length = 0x1F800 – address.
Ownership: When the driver assumes ownership of a buffer, it means that the driver has the capability to perform random read/write operations on the buffer (often via DMA). The application should not read/write the buffer until the ownership is returned to the application. If the application reads from a buffer owned by a receiving driver, the data read can be random; similarly, if the application writes to a buffer owned by a sending driver, the data sent may be corrupted.
Requested length: The length requested in one transfer determined by the FIFO address.
Transfer length: The length requested in one transfer determined by the CMD53 byte/block count field.
Note
Requested length is different from the transfer length. In the context of ESP32 SDIO slave DMA, the operation is based on the requested length rather than the transfer length. This means the DMA controller will process the data transfer according to the requested length, ensuring that only data within the requested length is transferred. The transfer length should be no shorter than the requested length, and the rest part is filled with 0 during sending or discard during receiving.
Receiving buffer size: The buffer size is pre-defined between the host and the slave before communication starts. The slave application has to set the buffer size during initialization by the
recv_buffer_size
parameter in thesdio_slave_config_t
structure.Interrupts: The ESP32 SDIO slave supports interrupts in two directions: from host to slave (referred to as slave interrupts) and from slave to host (referred to as host interrupts). For more details, refer to Interrupts.
Registers: Specific addresses in Function 1 accessed by CMD52 or CMD53.
Communication with ESP SDIO Slave
The host should initialize the ESP32 SDIO slave according to the standard SDIO initialization process (Sector 3.1.2 of SDIO Simplified Specification), which is described briefly in ESP SDIO Slave Initialization.
Furthermore, there is an ESP32-specific upper-level communication protocol built upon the foundation of CMD52/CMD53 to Function 1. Within this particular communication protocol, the master and slave engage in data exchange and communication through the utilization of CMD52/CMD53 commands. For more detailed information, please consult the ESP SDIO Slave Protocol section.
There is also a component ESP Serial Slave Link designed for ESP32 master to communicate with ESP32 SDIO slave. See example peripherals/sdio when programming your host.
Interrupts
There are interrupts from host to slave, and from slave to host to help communicating conveniently.
Slave Interrupts
The host can trigger an interruption in the slave by writing a single bit to the 0x08D register. As soon as any bit within the register is set, an interrupt is generated, prompting the SDIO slave driver to invoke the callback function specified in the slave_intr_cb
member of the sdio_slave_config_t
structure.
Note
The callback function is called in the ISR. Do not use any delay, loop or blocking function in the callback, e.g., mutex.
Similar to the previous information, there's an alternative set of functions available. You can call sdio_slave_wait_int
to wait for an interrupt within a certain time, or call sdio_slave_clear_int
to clear interrupts from host. The callback function can work with the wait functions perfectly.
Host Interrupts
The slave can interrupt the host by an interrupt line at certain time, which is level-sensitive, i.e., the interrupt signal can be triggered by detecting the level change of the interrupt line. When the host see the interrupt line pulled down, it may read the slave interrupt status register, to see the interrupt source. Host can clear interrupt bits, or choose to disable a interrupt source. The interrupt line holds active until all the sources are cleared or disabled.
There are several dedicated interrupt sources as well as general-purpose sources. see sdio_slave_hostint_t
for more information.
Receiving FIFO
When the host is going to send the slave some packets, it has to check whether the slave is ready to receive by reading the buffer number of slave.
To allow the host sending data to the slave, the application has to load buffers to the slave driver by the following steps:
Register the buffer by calling
sdio_slave_recv_register_buf
, and get the handle of the registered buffer. The driver allocates memory for the linked-list descriptor needed to link the buffer onto the hardware. The size of these buffers should equal to the Receiving buffer size.Load buffers onto the driver by passing the buffer handle to
sdio_slave_recv_load_buf
.Get the received data by calling
sdio_slave_recv
orsdio_slave_recv_packet
. If a non-blocking call is needed, setwait=0
.The difference between two APIs is that,
sdio_slave_recv_packet
gives more information about packet, which can consist of several buffers.When
ESP_ERR_NOT_FINISHED
is returned by this API, you should call this API iteratively until the return value isESP_OK
. All the continuous buffers returned withESP_ERR_NOT_FINISHED
, together with the last buffer returned withESP_OK
, belong to one packet from the host.Call
sdio_slave_recv_get_buf
to get the address of the received data, and the actual length received in each buffer. The packet length is the sum of received length of all the buffers in the packet.If the host never send data longer than the Receiving buffer size, or you do not care about the packet boundary (e.g., the data is only a byte stream), you can call the simpler version
sdio_slave_recv
instead.Pass the handle of processed buffer back to the driver by
sdio_recv_load_buf
again.
Note
To minimize data copying overhead, the driver itself does not maintain any internal buffer; it is the responsibility of the application to promptly provide new buffers. The DMA system automatically stores received data into these buffers.
Sending FIFO
Each time the slave has data to send, it raises an interrupt, and the host requests the packet length. There are two sending modes:
Stream Mode: When a buffer is loaded into the driver, the buffer length is included into the packet length requested by host in the incoming communications. This is irrespective of whether previous packets have been sent or not. In other words, the length of the newly loaded buffer is included into the length of the packet requested by the host, even if there are previously unsent packets. This enables the host to receive data from several buffers in a single transfer.
Packet Mode: The packet length is updated packet by packet, and only when previous packet is sent. This means that the host can only get data of one buffer in one transfer.
Note
To avoid overhead from copying data, the driver itself does not have any buffer inside. Namely, the DMA takes data directly from the buffer provided by the application. The application should not touch the buffer until the sending is finished, so as to ensure that the data is transferred correctly.
The sending mode can be set in the sending_mode
member of sdio_slave_config_t
, and the buffer numbers can be set in the send_queue_size
. All the buffers are restricted to be no larger than 4092 bytes. Though in the stream mode, several buffers can be sent in one transfer, each buffer is still counted as one in the queue.
The application can call sdio_slave_transmit
to send packets. In this case, the function returns when the transfer is successfully done, so the queue is not fully used. When higher efficiency is required, the application can use the following functions instead:
Pass buffer information (address, length, as well as an
arg
indicating the buffer) tosdio_slave_send_queue
.If non-blocking call is needed, set
wait=0
.If the
wait
is notportMAX_DELAY
(wait until success), application has to check the result to know whether the data is put in to the queue or discard.
Call
sdio_slave_send_get_finished
to get and deal with a finished transfer. A buffer should be kept unmodified until returned fromsdio_slave_send_get_finished
. This means the buffer is actually sent to the host, rather than just staying in the queue.
There are several ways to use the arg
in the queue parameter:
Directly point
arg
to a dynamic-allocated buffer, and use thearg
to free it when transfer finished.Wrap transfer information in a transfer structure, and point
arg
to the structure. You can use the structure to do more things like:typedef struct { uint8_t* buffer; size_t size; int id; }sdio_transfer_t; //and send as: sdio_transfer_t trans = { .buffer = ADDRESS_TO_SEND, .size = 8, .id = 3, //the 3rd transfer so far }; sdio_slave_send_queue(trans.buffer, trans.size, &trans, portMAX_DELAY); //... maybe more transfers are sent here //and deal with finished transfer as: sdio_transfer_t* arg = NULL; sdio_slave_send_get_finished((void**)&arg, portMAX_DELAY); ESP_LOGI("tag", "(%d) successfully send %d bytes of %p", arg->id, arg->size, arg->buffer); some_post_callback(arg); //do more thingsWork with the receiving part of this driver, and point
arg
to the receive buffer handle of this buffer, so that we can directly use the buffer to receive data when it is sent:uint8_t buffer[256]={1,2,3,4,5,6,7,8}; sdio_slave_buf_handle_t handle = sdio_slave_recv_register_buf(buffer); sdio_slave_send_queue(buffer, 8, handle, portMAX_DELAY); //... maybe more transfers are sent here //and load finished buffer to receive as sdio_slave_buf_handle_t handle = NULL; sdio_slave_send_get_finished((void**)&handle, portMAX_DELAY); sdio_slave_recv_load_buf(handle);For more about this, see peripherals/sdio.
Application Example
peripherals/sdio/host and peripherals/sdio/slave demonstrate how to use a host to communicate with an ESP SDIO slave device.
API Reference
Header File
This header file can be included with:
#include "hal/sdio_slave_types.h"
Enumerations
-
enum sdio_slave_hostint_t
Mask of interrupts sending to the host.
Values:
-
enumerator SDIO_SLAVE_HOSTINT_BIT0
General purpose interrupt bit 0.
-
enumerator SDIO_SLAVE_HOSTINT_BIT1
-
enumerator SDIO_SLAVE_HOSTINT_BIT2
-
enumerator SDIO_SLAVE_HOSTINT_BIT3
-
enumerator SDIO_SLAVE_HOSTINT_BIT4
-
enumerator SDIO_SLAVE_HOSTINT_BIT5
-
enumerator SDIO_SLAVE_HOSTINT_BIT6
-
enumerator SDIO_SLAVE_HOSTINT_BIT7
-
enumerator SDIO_SLAVE_HOSTINT_SEND_NEW_PACKET
New packet available.
-
enumerator SDIO_SLAVE_HOSTINT_BIT0
-
enum sdio_slave_timing_t
Timing of SDIO slave.
Values:
-
enumerator SDIO_SLAVE_TIMING_PSEND_PSAMPLE
Send at posedge, and sample at posedge. Default value for HS mode. If :c:macro:
SDIO_SLAVE_FLAG_HIGH_SPEED
is specified in :cpp:class:sdio_slave_config_t
, this should be selected. Normally there's no problem using this to work in DS mode.
-
enumerator SDIO_SLAVE_TIMING_NSEND_PSAMPLE
Send at negedge, and sample at posedge. Default value for DS mode and below. If :c:macro:
SDIO_SLAVE_FLAG_DEFAULT_SPEED
is specified in :cpp:class:sdio_slave_config_t
, this should be selected.
-
enumerator SDIO_SLAVE_TIMING_PSEND_NSAMPLE
Send at posedge, and sample at negedge.
-
enumerator SDIO_SLAVE_TIMING_NSEND_NSAMPLE
Send at negedge, and sample at negedge.
-
enumerator SDIO_SLAVE_TIMING_PSEND_PSAMPLE
-
enum sdio_slave_sending_mode_t
Configuration of SDIO slave mode.
Values:
-
enumerator SDIO_SLAVE_SEND_STREAM
Stream mode, all packets to send will be combined as one if possible.
-
enumerator SDIO_SLAVE_SEND_PACKET
Packet mode, one packets will be sent one after another (only increase packet_len if last packet sent).
-
enumerator SDIO_SLAVE_SEND_STREAM
Header File
This header file can be included with:
#include "driver/sdio_slave.h"
This header file is a part of the API provided by the
esp_driver_sdio
component. To declare that your component depends onesp_driver_sdio
, add the following to your CMakeLists.txt:REQUIRES esp_driver_sdio
or
PRIV_REQUIRES esp_driver_sdio
Functions
-
esp_err_t sdio_slave_initialize(sdio_slave_config_t *config)
Initialize the sdio slave driver
- Parameters
config -- Configuration of the sdio slave driver.
- Returns
ESP_ERR_NOT_FOUND if no free interrupt found.
ESP_ERR_INVALID_STATE if already initialized.
ESP_ERR_NO_MEM if fail due to memory allocation failed.
ESP_OK if success
-
void sdio_slave_deinit(void)
De-initialize the sdio slave driver to release the resources.
-
esp_err_t sdio_slave_start(void)
Start hardware for sending and receiving, as well as set the IOREADY1 to 1.
Note
The driver will continue sending from previous data and PKT_LEN counting, keep data received as well as start receiving from current TOKEN1 counting. See
sdio_slave_reset
.- Returns
ESP_ERR_INVALID_STATE if already started.
ESP_OK otherwise.
-
void sdio_slave_stop(void)
Stop hardware from sending and receiving, also set IOREADY1 to 0.
Note
this will not clear the data already in the driver, and also not reset the PKT_LEN and TOKEN1 counting. Call
sdio_slave_reset
to do that.
-
esp_err_t sdio_slave_reset(void)
Clear the data still in the driver, as well as reset the PKT_LEN and TOKEN1 counting.
- Returns
always return ESP_OK.
-
sdio_slave_buf_handle_t sdio_slave_recv_register_buf(uint8_t *start)
Register buffer used for receiving. All buffers should be registered before used, and then can be used (again) in the driver by the handle returned.
Note
The driver will use and only use the amount of space specified in the
recv_buffer_size
member set in thesdio_slave_config_t
. All buffers should be larger than that. The buffer is used by the DMA, so it should be DMA capable and 32-bit aligned.- Parameters
start -- The start address of the buffer.
- Returns
The buffer handle if success, otherwise NULL.
-
esp_err_t sdio_slave_recv_unregister_buf(sdio_slave_buf_handle_t handle)
Unregister buffer from driver, and free the space used by the descriptor pointing to the buffer.
- Parameters
handle -- Handle to the buffer to release.
- Returns
ESP_OK if success, ESP_ERR_INVALID_ARG if the handle is NULL or the buffer is being used.
-
esp_err_t sdio_slave_recv_load_buf(sdio_slave_buf_handle_t handle)
Load buffer to the queue waiting to receive data. The driver takes ownership of the buffer until the buffer is returned by
sdio_slave_send_get_finished
after the transaction is finished.- Parameters
handle -- Handle to the buffer ready to receive data.
- Returns
ESP_ERR_INVALID_ARG if invalid handle or the buffer is already in the queue. Only after the buffer is returened by
sdio_slave_recv
can you load it again.ESP_OK if success
-
esp_err_t sdio_slave_recv_packet(sdio_slave_buf_handle_t *handle_ret, TickType_t wait)
Get buffer of received data if exist with packet information. The driver returns the ownership of the buffer to the app.
When you see return value is
ESP_ERR_NOT_FINISHED
, you should call this API iteratively until the return value isESP_OK
. All the continuous buffers returned withESP_ERR_NOT_FINISHED
, together with the last buffer returned withESP_OK
, belong to one packet from the host.You can call simpler
sdio_slave_recv
instead, if the host never send data longer than the Receiving buffer size, or you don't care about the packet boundary (e.g. the data is only a byte stream).Note
Call
sdio_slave_load_buf
with the handle to re-load the buffer onto the link list, and receive with the same buffer again. The address and length of the buffer got here is the same as got fromsdio_slave_get_buffer
.- Parameters
handle_ret -- Handle of the buffer holding received data. Use this handle in
sdio_slave_recv_load_buf()
to receive in the same buffer again.wait -- Time to wait before data received.
- Returns
ESP_ERR_INVALID_ARG if handle_ret is NULL
ESP_ERR_TIMEOUT if timeout before receiving new data
ESP_ERR_NOT_FINISHED if returned buffer is not the end of a packet from the host, should call this API again until the end of a packet
ESP_OK if success
-
esp_err_t sdio_slave_recv(sdio_slave_buf_handle_t *handle_ret, uint8_t **out_addr, size_t *out_len, TickType_t wait)
Get received data if exist. The driver returns the ownership of the buffer to the app.
Note
Call
sdio_slave_load_buf
with the handle to re-load the buffer onto the link list, and receive with the same buffer again. The address and length of the buffer got here is the same as got fromsdio_slave_get_buffer
.- Parameters
handle_ret -- Handle to the buffer holding received data. Use this handle in
sdio_slave_recv_load_buf
to receive in the same buffer again.out_addr -- [out] Output of the start address, set to NULL if not needed.
out_len -- [out] Actual length of the data in the buffer, set to NULL if not needed.
wait -- Time to wait before data received.
- Returns
ESP_ERR_INVALID_ARG if handle_ret is NULL
ESP_ERR_TIMEOUT if timeout before receiving new data
ESP_OK if success
-
uint8_t *sdio_slave_recv_get_buf(sdio_slave_buf_handle_t handle, size_t *len_o)
Retrieve the buffer corresponding to a handle.
- Parameters
handle -- Handle to get the buffer.
len_o -- Output of buffer length
- Returns
buffer address if success, otherwise NULL.
-
esp_err_t sdio_slave_send_queue(uint8_t *addr, size_t len, void *arg, TickType_t wait)
Put a new sending transfer into the send queue. The driver takes ownership of the buffer until the buffer is returned by
sdio_slave_send_get_finished
after the transaction is finished.- Parameters
addr -- Address for data to be sent. The buffer should be DMA capable and 32-bit aligned.
len -- Length of the data, should not be longer than 4092 bytes (may support longer in the future).
arg -- Argument to returned in
sdio_slave_send_get_finished
. The argument can be used to indicate which transaction is done, or as a parameter for a callback. Set to NULL if not needed.wait -- Time to wait if the buffer is full.
- Returns
ESP_ERR_INVALID_ARG if the length is not greater than 0.
ESP_ERR_TIMEOUT if the queue is still full until timeout.
ESP_OK if success.
-
esp_err_t sdio_slave_send_get_finished(void **out_arg, TickType_t wait)
Return the ownership of a finished transaction.
- Parameters
out_arg -- Argument of the finished transaction. Set to NULL if unused.
wait -- Time to wait if there's no finished sending transaction.
- Returns
ESP_ERR_TIMEOUT if no transaction finished, or ESP_OK if succeed.
-
esp_err_t sdio_slave_transmit(uint8_t *addr, size_t len)
Start a new sending transfer, and wait for it (blocked) to be finished.
- Parameters
addr -- Start address of the buffer to send
len -- Length of buffer to send.
- Returns
ESP_ERR_INVALID_ARG if the length of descriptor is not greater than 0.
ESP_ERR_TIMEOUT if the queue is full or host do not start a transfer before timeout.
ESP_OK if success.
-
uint8_t sdio_slave_read_reg(int pos)
Read the spi slave register shared with host.
Note
register 28 to 31 are reserved for interrupt vector.
- Parameters
pos -- register address, 0-27 or 32-63.
- Returns
value of the register.
-
esp_err_t sdio_slave_write_reg(int pos, uint8_t reg)
Write the spi slave register shared with host.
Note
register 29 and 31 are used for interrupt vector.
- Parameters
pos -- register address, 0-11, 14-15, 18-19, 24-27 and 32-63, other address are reserved.
reg -- the value to write.
- Returns
ESP_ERR_INVALID_ARG if address wrong, otherwise ESP_OK.
Get the interrupt enable for host.
- Returns
the interrupt mask.
-
void sdio_slave_set_host_intena(sdio_slave_hostint_t mask)
Set the interrupt enable for host.
- Parameters
mask -- Enable mask for host interrupt.
-
esp_err_t sdio_slave_send_host_int(uint8_t pos)
Interrupt the host by general purpose interrupt.
- Parameters
pos -- Interrupt num, 0-7.
- Returns
ESP_ERR_INVALID_ARG if interrupt num error
ESP_OK otherwise
-
void sdio_slave_clear_host_int(sdio_slave_hostint_t mask)
Clear general purpose interrupt to host.
- Parameters
mask -- Interrupt bits to clear, by bit mask.
-
esp_err_t sdio_slave_wait_int(int pos, TickType_t wait)
Wait for general purpose interrupt from host.
Note
this clears the interrupt at the same time.
- Parameters
pos -- Interrupt source number to wait for. is set.
wait -- Time to wait before interrupt triggered.
- Returns
ESP_OK if success, ESP_ERR_TIMEOUT if timeout.
Structures
-
struct sdio_slave_config_t
Configuration of SDIO slave.
Public Members
-
sdio_slave_timing_t timing
timing of sdio_slave. see
sdio_slave_timing_t
.
-
sdio_slave_sending_mode_t sending_mode
mode of sdio_slave.
SDIO_SLAVE_MODE_STREAM
if the data needs to be sent as much as possible;SDIO_SLAVE_MODE_PACKET
if the data should be sent in packets.
-
int send_queue_size
max buffers that can be queued before sending.
-
size_t recv_buffer_size
If buffer_size is too small, it costs more CPU time to handle larger number of buffers. If buffer_size is too large, the space larger than the transaction length is left blank but still counts a buffer, and the buffers are easily run out. Should be set according to length of data really transferred. All data that do not fully fill a buffer is still counted as one buffer. E.g. 10 bytes data costs 2 buffers if the size is 8 bytes per buffer. Buffer size of the slave pre-defined between host and slave before communication. All receive buffer given to the driver should be larger than this.
-
sdio_event_cb_t event_cb
when the host interrupts slave, this callback will be called with interrupt number (0-7).
-
uint32_t flags
Features to be enabled for the slave, combinations of
SDIO_SLAVE_FLAG_*
.
-
sdio_slave_timing_t timing
Macros
-
SDIO_SLAVE_RECV_MAX_BUFFER
-
SDIO_SLAVE_FLAG_DAT2_DISABLED
It is required by the SD specification that all 4 data lines should be used and pulled up even in 1-bit mode or SPI mode. However, as a feature, the user can specify this flag to make use of DAT2 pin in 1-bit mode. Note that the host cannot read CCCR registers to know we don't support 4-bit mode anymore, please do this at your own risk.
-
SDIO_SLAVE_FLAG_HOST_INTR_DISABLED
The DAT1 line is used as the interrupt line in SDIO protocol. However, as a feature, the user can specify this flag to make use of DAT1 pin of the slave in 1-bit mode. Note that the host has to do polling to the interrupt registers to know whether there are interrupts from the slave. And it cannot read CCCR registers to know we don't support 4-bit mode anymore, please do this at your own risk.
-
SDIO_SLAVE_FLAG_INTERNAL_PULLUP
Enable internal pullups for enabled pins. It is required by the SD specification that all the 4 data lines should be pulled up even in 1-bit mode or SPI mode. Note that the internal pull-ups are not sufficient for stable communication, please do connect external pull-ups on the bus. This is only for example and debug use.
-
SDIO_SLAVE_FLAG_DEFAULT_SPEED
Disable the highspeed support of the hardware.
-
SDIO_SLAVE_FLAG_HIGH_SPEED
Enable the highspeed support of the hardware. This is the default option. The host will see highspeed capability, but the mode actually used is determined by the host.
Type Definitions
-
typedef void (*sdio_event_cb_t)(uint8_t event)
-
typedef void *sdio_slave_buf_handle_t
Handle of a receive buffer, register a handle by calling
sdio_slave_recv_register_buf
. Use the handle to load the buffer to the driver, or callsdio_slave_recv_unregister_buf
if it is no longer used.