cpu/esp8266: allow arbitrary SPI clocks#20410
Conversation
benpicco
added
Type: enhancement
github-actions
bot
added
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; | ||
|
|
There was a problem hiding this comment.
Why was this change necessary if the enum values are (no longer?) used?
There was a problem hiding this comment.
The enum values only go from 0 to 4, with this you can just write the desired SPI frequency to the clk parameter instead.
There was a problem hiding this comment.
Where is the original enum definition? I somehow doubt it is a good idea to override those only for a single platform?
There was a problem hiding this comment.
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.
There was a problem hiding this comment.
Hum, maybe worth an issue to clean up the original interface then in a subsequent PR?
There was a problem hiding this comment.
We might introduce a new feature for platforms where you can select arbitrary SPI clocks, so drivers can rely on this.
Teufelchen1
left a comment
Teufelchen1
left a comment
There was a problem hiding this comment.
I did not test this physically.
|
Sorry, #20438 will never get in if every merge conflicts and kicks it out. I will requeue when ready. |
5 participants
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