Zephyr API for getting SPI reading data length

RE: Zephyr API for getting SPI reading data length

Jørgen Holmefjord — Fri, 29 Sep 2023 15:07:43 GMT

As long as you are the master, you decide how much data should be read out from the slave. If the slave only have 100bytes to clock out, and you read 300 bytes, the slave will typically clock out the ORC for the remaining 200 bytes. This is implementation dependent, and should be specified in the datasheet of the SPI slave device.

RE: Zephyr API for getting SPI reading data length

snowuyl — Wed, 27 Sep 2023 14:45:28 GMT

Thanks for your reply! If I request more data than actual data (E.g. I request 300 bytes data, but only 100 bytes), what will happen?

RE: Zephyr API for getting SPI reading data length

Jørgen Holmefjord — Wed, 27 Sep 2023 14:19:18 GMT

spi_buf_set is a struct that contains a pointer to the buffer and the count of number of bytes in the buffer. The function will not return the actual read length, but the read length will always be what you request when calling the function.

RE: Zephyr API for getting SPI reading data length

snowuyl — Wed, 27 Sep 2023 12:48:29 GMT

Thanks for your reply! From spi_read (const struct device*dev, const struct spi_config*config, const struct spi_buf_set*rx_bufs), how to decide rx_bugs array size and does spi_read() returns actual reading data length?

RE: Zephyr API for getting SPI reading data length

Jørgen Holmefjord — Wed, 27 Sep 2023 12:26:13 GMT

Hi,

What do you mean by this?

[quote user=""]can't find any API can get reading data length[/quote]

The API spi_read() is used to read a specified number if bytes on the SPI bus.

Best regards,
Jørgen