Merge branch 'feat/sdio_slave_init_doc' into 'master'

sdio_slave: add documentation for the standard init process

See merge request idf/esp-idf!3548
This commit is contained in:
Angus Gratton 2018-10-29 09:07:30 +08:00
commit 7efbe8178b
2 changed files with 94 additions and 12 deletions

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@ -1,5 +1,79 @@
Communication with ESP SDIO Slave
====================================
.. _esp_slave_init:
ESP SDIO slave initialization
------------------------------
The host should initialize the ESP32 SDIO slave according to the standard
SDIO initialization process (Sector 3.1.2 of `SDIO Simplified
Specification <https://www.sdcard.org/downloads/pls/>`_). In this specification
and below, the SDIO slave is also called an (SD)IO card. All the
initialization CMD52 and CMD53 are sent to Func 0 (CIA region). Here is an
brief example on how to do this:
1. SDIO reset
CMD52 (Write 0x6=0x8)
2. SD reset
CMD0
3. Check whether IO card (optional)
CMD8
4. Send SDIO op cond and wait for card ready
CMD5 arg = 0x00000000
CMD5 arg = 0x00ff8000 (according to the response above, poll until ready)
**Example:**
Arg of R4 after first CMD5 (arg=0x00000000) is 0xXXFFFF00.
Keep sending CMD5 with arg=0x00FFFF00 until the R4 shows card ready (arg bit 31=1).
5. Set address
CMD3
6. Select card
CMD7 (arg address according to CMD3 response)
**Example:**
Arg of R6 after CMD3 is 0x0001xxxx.
Arg of CMD7 should be 0x00010000.
7. Select 4-bit mode (optional)
CMD52 (Write 0x07=0x02)
8. Enable func1
CMD52 (Write 0x02=0x02)
9. Enable SDIO interrupt (required if interrupt line (DAT1) is used)
CMD52 (Write 0x04=0x03)
10. Set Func0 blocksize (optional, default value is 512 (0x200))
CMD52/53 (Read 0x10~0x11)
CMD52/53 (Write 0x10=0x00)
CMD52/53 (Write 0x11=0x02)
CMD52/53 (Read 0x10~0x11, read to check the final value)
11. Set Func1 blocksize (optional, default value is 512 (0x200))
CMD52/53 (Read 0x110~0x111)
CMD52/53 (Write 0x110=0x00)
CMD52/53 (Write 0x111=0x02)
CMD52/53 (Read 0x110~0x111, read to check the final value)
.. _esp_slave_protocol_layer:
ESP SDIO slave protocol
=======================
-----------------------
The protocol is based on Function 1 access by CMD52 and CMD53, offering 3 services: (1) sending and receiving FIFO, (2) 52 8-bit R/W
register shared by host and slave, (3) 8 general purpose interrupt sources from host to slave and 8 in the oppsite direction.
@ -7,10 +81,11 @@ register shared by host and slave, (3) 8 general purpose interrupt sources from
The host should access the registers below as described to communicate with slave.
Slave register table
--------------------
^^^^^^^^^^^^^^^^^^^^
32-bit
^^^^^^^
#######
- 0x044 (TOKEN_RDATA): in which bit 27-16 holds the receiving buffer number.
- 0x058 (INT_ST): holds the interrupt source bits from slave to host.
- 0x060 (PKT_LEN): holds the accumulated length (by byte) to be sent from slave to host.
@ -18,7 +93,8 @@ Slave register table
- 0x0DC (INT_ENA): mask bits for interrupts from slave to host.
8-bit
^^^^^
#####
Shared general purpose registers:
- 0x06C-0x077: R/W registers 0-11 shared by slave and host.
@ -31,7 +107,7 @@ Interrupt Registers:
- 0x08D (SLAVE_INT): bits for host to interrupt slave. auto clear.
FIFO (sending and receiving)
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
############################
0x090 - 0x1F7FF are reserved for FIFOs.
@ -59,7 +135,7 @@ or discard (receiving).
supports that) to address 0x1F7F9=0x1F800-**7**.
Interrupts
----------
^^^^^^^^^^
For the host interrupts, the slave raise the interrupt by pulling DAT1 line down at a proper time (level sensitive).
The host detect this and read the INT_ST register to see the source. Then the host can clear it by writing the INT_CLR
@ -72,7 +148,7 @@ For the slave interrupts, the host send transfers to write the SLAVE_INT registe
the slave hardware and driver will detect it and inform the app.
Receiving FIFO
--------------
^^^^^^^^^^^^^^
To write the receiving FIFO in the slave, host should work in the following steps:
@ -86,7 +162,7 @@ To write the receiving FIFO in the slave, host should work in the following step
4. Calculate used buffers, note that non-full buffer at the tail should be seen as one that is used.
Sending FIFO
------------
^^^^^^^^^^^^
To read the sending FIFO in the slave, host should work in the following steps:

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@ -89,11 +89,17 @@ The SDIO slave driver uses the following terms:
and from slave to host (called host interrupts below). See more in :ref:`interrupts`.
- Registers: specific address in Function 1 access by CMD52 or CMD53.
ESP SDIO Slave Protocol
^^^^^^^^^^^^^^^^^^^^^^^
Communication with ESP SDIO Slave
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The communication protocol slave used to communicate with the host is ESP32 specific, please refer to
:doc:`esp_slave_protocol`, or example :example:`peripherals/sdio` for designing a host.
The host should initialize the ESP32 SDIO slave according to the standard
SDIO initialization process (Sector 3.1.2 of `SDIO Simplified
Specification <https://www.sdcard.org/downloads/pls/>`_), which is described
briefly in :ref:`esp_slave_init`.
However, there's an ESP32-specific upper-level communication protocol upon
the CMD52/CMD53 to Func 1. Please refer to :ref:`esp_slave_protocol_layer`,
or example :example:`peripherals/sdio` when programming your host.
.. toctree::
:hidden: