essl_spi_rdbuf() function

Read the shared buffer from the slave in ISR way

Syntax

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Summary

Declaration

Definition

from essl_spi.h:157

esp_err_t essl_spi_rdbuf(spi_device_handle_t spi, uint8_t *out_data, int addr, int len, uint32_t flags);

Implemented in essl_spi.c:99

Arguments

Argument

Description

spi

SPI device handle representing the slave

out_data

Buffer for read data, strongly suggested to be in the DRAM and aligned to 4

addr

Address of the slave shared buffer

len

Length to read

flags

`SPI_TRANS_*` flags to control the transaction mode of the transaction to send.

Return value

- ESP_OK: on success - or other return value from :cpp:func:`spi_device_transmit`.

Notes

The slave's HW doesn't guarantee the data in one SPI transaction is consistent. It sends data in unit of byte. In other words, if the slave SW attempts to update the shared register when a rdbuf SPI transaction is in-flight, the data got by the master will be the combination of bytes of different writes of slave SW. ``out_data`` should be prepared in words and in the DRAM. The buffer may be written in words by the DMA. When a byte is written, the remaining bytes in the same word will also be overwritten, even the ``len`` is shorter than a word.