cpu/esp8266: allow arbitrary SPI clocks #20410
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benpicco
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Type: enhancement
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Platform: ESP
| /** | ||
| * @brief Override SPI clock speed values | ||
| * @{ | ||
| */ | ||
| #define HAVE_SPI_CLK_T | ||
| typedef enum { | ||
| SPI_CLK_100KHZ = KHZ(100), /**< drive the SPI bus with 100KHz */ | ||
| SPI_CLK_400KHZ = KHZ(400), /**< drive the SPI bus with 400KHz */ | ||
| SPI_CLK_1MHZ = MHZ(1), /**< drive the SPI bus with 1MHz */ | ||
| SPI_CLK_5MHZ = MHZ(5), /**< drive the SPI bus with 5MHz */ | ||
| SPI_CLK_10MHZ = MHZ(10), /**< drive the SPI bus with 10MHz */ | ||
| } spi_clk_t; | ||
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Why was this change necessary if the enum values are (no longer?) used?
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The enum values only go from 0 to 4, with this you can just write the desired SPI frequency to the clk parameter instead.
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Where is the original enum definition? I somehow doubt it is a good idea to override those only for a single platform?
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The previous definition was here - you will find that overwriting this is done by most platforms already since the original interface is pretty bad/limiting.
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Hum, maybe worth an issue to clean up the original interface then in a subsequent PR?
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We might introduce a new feature for platforms where you can select arbitrary SPI clocks, so drivers can rely on this.
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Sorry, #20438 will never get in if every merge conflicts and kicks it out. I will requeue when ready. |
Contribution description
The formula for the ESP8266 SPI clock is
clk_spi = clk_src / ((prediv + 1) * (N + 1))where N has to be at least 1.Since
predivis 13 bit, this gets us down to 4882 Hz without further touching N, so just use that.Testing procedure
I connected an oscilloscope to the clock pin of
esp8266-esp-12xand tried out all pre-defined SPI clocks withtests/periph/spi:100 kHz
400 kHz
1 MHz
5 MHz
10 MHz
Issues/PRs references
useful for #20218