Chapter 2. API Reference
• handle: Device handle obtained using spi_host_add_dev
• trans_desc: Pointer to variable able to contain a pointer to the description of the transac-
tion that is executed. The descriptor should not be modified until the descriptor is returned by
spi_device_get_trans_result.
• ticks_to_wait: Ticks to wait until there’s a returned item; use portMAX_DELAY to never
time out.
esp_err_t spi_device_transmit(spi_device_handle_t handle, spi_transaction_t *trans_desc)
Send a SPI transaction, wait for it to complete, and return the result.
This function is the equivalent of calling spi_device_queue_trans() followed by spi_device_get_trans_result().
Do not use this when there is still a transaction separately queued (started) from spi_device_queue_trans() or
polling_start/transmit that hasn’t been finalized.
Note This function is not thread safe when multiple tasks access the same SPI device. Normally a device
cannot start (queue) polling and interrupt transactions simutanuously.
Return
• ESP_ERR_INVALID_ARG if parameter is invalid
• ESP_OK on success
Parameters
• handle: Device handle obtained using spi_host_add_dev
• trans_desc: Description of transaction to execute
esp_err_t spi_device_polling_start(spi_device_handle_t handle, spi_transaction_t *trans_desc,
TickType_t ticks_to_wait)
Immediately start a polling transaction.
Note Normally a device cannot start (queue) polling and interrupt transactions simutanuously. Moreover, a
device cannot start a new polling transaction if another polling transaction is not finished.
Return
• ESP_ERR_INVALID_ARG if parameter is invalid. This can happen if
SPI_TRANS_CS_KEEP_ACTIVE flag is specified while the bus was not acquired
(spi_device_acquire_bus() should be called first)
• ESP_ERR_TIMEOUT if the device cannot get control of the bus before ticks_to_wait expired
• ESP_ERR_NO_MEM if allocating DMA-capable temporary buffer failed
• ESP_ERR_INVALID_STATE if previous transactions are not finished
• ESP_OK on success
Parameters
• handle: Device handle obtained using spi_host_add_dev
• trans_desc: Description of transaction to execute
• ticks_to_wait: Ticks to wait until there’s room in the queue; currently only port-
MAX_DELAY is supported.
esp_err_t spi_device_polling_end(spi_device_handle_t handle, TickType_t ticks_to_wait)
Poll until the polling transaction ends.
This routine will not return until the transaction to the given device has succesfully completed. The task is not
blocked, but actively busy-spins for the transaction to be completed.
Return
• ESP_ERR_INVALID_ARG if parameter is invalid
• ESP_ERR_TIMEOUT if the transaction cannot finish before ticks_to_wait expired
• ESP_OK on success
Parameters
• handle: Device handle obtained using spi_host_add_dev
• ticks_to_wait: Ticks to wait until there’s a returned item; use portMAX_DELAY to never
time out.
esp_err_t spi_device_polling_transmit(spi_device_handle_t handle, spi_transaction_t
*trans_desc)
Send a polling transaction, wait for it to complete, and return the result.
This function is the equivalent of calling spi_device_polling_start() followed by spi_device_polling_end(). Do
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