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rmt: add open-drain flag on tx channel

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wangyuanze
2022-07-04 14:59:45 +08:00
committed by morris
parent 8944479bcd
commit ab0c4abd6e
3 changed files with 6 additions and 4 deletions
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docs/en/api-reference/peripherals/rmt.rst
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@@ -82,7 +82,8 @@ To install an RMT TX channel, there's a configuration structure that needs to be
- :cpp:member:`rmt_tx_channel_config_t::trans_queue_depth` sets the depth of internal transaction queue, the deeper the queue, the more transactions can be prepared in the backlog.
- :cpp:member:`rmt_tx_channel_config_t::invert_out` is used to decide whether to invert the RMT signal before sending it to the GPIO pad.
- :cpp:member:`rmt_tx_channel_config_t::with_dma` is used to indicate if the channel needs a DMA backend. A channel with DMA attached can offload the CPU by a lot. However, DMA backend is not available on all ESP chips, please refer to [`TRM <{IDF_TARGET_TRM_EN_URL}#rmt>`__] before you enable this option. Or you might encounter :c:macro:`ESP_ERR_NOT_SUPPORTED` error.
- :cpp:member:`rmt_tx_channel_config_t::io_loop_back` is for debugging purposes only. It enables both the GPIO's input and output ability through the GPIO matrix peripheral. Meanwhile, if both TX and RX channels are bound to the same GPIO, then monitoring of the data transmission line can be realized.
- :cpp:member:`rmt_tx_channel_config_t::io_loop_back` enables both the GPIO's input and output ability through the GPIO matrix peripheral. Meanwhile, if both TX and RX channels are bound to the same GPIO, then monitoring of the data transmission line can be realized.
- :cpp:member:`rmt_tx_channel_config_t::io_od_mode` configures the GPIO as open-drain mode. It is useful for simulating bi-directional buses, sucn as 1-wire bus, combined with :cpp:member:`rmt_tx_channel_config_t::io_loop_back`.
Once the :cpp:type:`rmt_tx_channel_config_t` structure is populated with mandatory parameters, users can call :cpp:func:`rmt_new_tx_channel` to allocate and initialize a TX channel. This function will return an RMT channel handle if it runs correctly. Specifically, when there are no more free channels in the RMT resource pool, this function will return :c:macro:`ESP_ERR_NOT_FOUND` error. If some feature (e.g. DMA backend) is not supported by hardware, it will return :c:macro:`ESP_ERR_NOT_SUPPORTED` error.