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Merge branch 'feat/spi_check_length_buffer' into 'master'

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spi: add checks for slave buffer valid and master length

See merge request idf/esp-idf!3744
This commit is contained in:
Jeroen Domburg
2018-12-04 11:48:32 +08:00
parent 2b557523ba cfba157fdd
commit d6ee27e313
6 changed files with 48 additions and 20 deletions
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docs/en/api-reference/peripherals/spi_slave.rst
+20 -10
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@@ -7,7 +7,7 @@ Overview
The ESP32 has four SPI peripheral devices, called SPI0, SPI1, HSPI and VSPI. SPI0 is entirely dedicated to
the flash cache the ESP32 uses to map the SPI flash device it is connected to into memory. SPI1 is
connected to the same hardware lines as SPI0 and is used to write to the flash chip. HSPI and VSPI
are free to use, and with the spi_slave driver, these can be used as a SPI slave, driven from a
are free to use, and with the spi_slave driver, these can be used as a SPI slave, driven from a
connected SPI master.
The spi_slave driver
@@ -21,9 +21,9 @@ Terminology
The spi_slave driver uses the following terms:
* Host: The SPI peripheral inside the ESP32 initiating the SPI transmissions. One of HSPI or VSPI.
* Host: The SPI peripheral inside the ESP32 initiating the SPI transmissions. One of HSPI or VSPI.
* Bus: The SPI bus, common to all SPI devices connected to a master. In general the bus consists of the
miso, mosi, sclk and optionally quadwp and quadhd signals. The SPI slaves are connected to these
miso, mosi, sclk and optionally quadwp and quadhd signals. The SPI slaves are connected to these
signals in parallel. Each SPI slave is also connected to one CS signal.
- miso - Also known as q, this is the output of the serial stream from the ESP32 to the SPI master
@@ -50,15 +50,15 @@ the master makes CS high again.
Using the spi_slave driver
^^^^^^^^^^^^^^^^^^^^^^^^^^^
- Initialize a SPI peripheral as a slave by calling ``spi_slave_initialize``. Make sure to set the
- Initialize a SPI peripheral as a slave by calling ``spi_slave_initialize``. Make sure to set the
correct IO pins in the ``bus_config`` struct. Take care to set signals that are not needed to -1.
A DMA channel (either 1 or 2) must be given if transactions will be larger than 32 bytes, if not
the dma_chan parameter may be 0.
- To set up a transaction, fill one or more spi_transaction_t structure with any transaction
- To set up a transaction, fill one or more spi_transaction_t structure with any transaction
parameters you need. Either queue all transactions by calling ``spi_slave_queue_trans``, later
quering the result using ``spi_slave_get_trans_result``, or handle all requests synchroneously
by feeding them into ``spi_slave_transmit``. The latter two functions will block until the
by feeding them into ``spi_slave_transmit``. The latter two functions will block until the
master has initiated and finished a transaction, causing the queued data to be sent and received.
- Optional: to unload the SPI slave driver, call ``spi_slave_free``.
@@ -69,7 +69,7 @@ Transaction data and master/slave length mismatches
Normally, data to be transferred to or from a device will be read from or written to a chunk of memory
indicated by the ``rx_buffer`` and ``tx_buffer`` members of the transaction structure. The SPI driver
may decide to use DMA for transfers, so these buffers should be allocated in DMA-capable memory using
may decide to use DMA for transfers, so these buffers should be allocated in DMA-capable memory using
``pvPortMallocCaps(size, MALLOC_CAP_DMA)``.
The amount of data written to the buffers is limited by the ``length`` member of the transaction structure:
@@ -78,13 +78,23 @@ length of the SPI transaction; this is determined by the master as it drives the
transferred can be read from the ``trans_len`` member of the ``spi_slave_transaction_t`` structure after transaction.
In case the length of the transmission is larger than the buffer length, only the start of the transmission
will be sent and received, and the ``trans_len`` is set to ``length`` instead of the actual length. It's recommended to
set ``length`` longer than the maximum length expected if the ``trans_len`` is required. In case the transmission
set ``length`` longer than the maximum length expected if the ``trans_len`` is required. In case the transmission
length is shorter than the buffer length, only data up to the length of the buffer will be exchanged.
Warning: Due to a design peculiarity in the ESP32, if the amount of bytes sent by the master or the length
of the transmission queues in the slave driver, in bytes, is not both larger than eight and dividable by
Warning: Due to a design peculiarity in the ESP32, if the amount of bytes sent by the master or the length
of the transmission queues in the slave driver, in bytes, is not both larger than eight and dividable by
four, the SPI hardware can fail to write the last one to seven bytes to the receive buffer.
Restrictions and Known issues
-------------------------------
1. If the DMA is enabled, the rx buffer should be WORD aligned, i.e. Start
from the boundary of 32-bit and have length of multiples of 4 bytes. Or the
DMA may write incorrectly or out of the boundary.The driver will check for
this.
Also, master should write lengths which are a multiple of 4 bytes. Data
longer than that will be discarded.
Application Example
-------------------