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spi_master: fix the timing a little so that can assign delay half clock manually

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This commit is contained in:
Michael (XIAO Xufeng) 2018-12-06 17:32:48 +08:00
parent 58955a79a2
commit 155006243e
1 changed files with 7 additions and 2 deletions
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9
components/driver/spi_master.c
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@ -380,11 +380,14 @@ esp_err_t spi_bus_free(spi_host_device_t host)
void spi_get_timing(bool gpio_is_used, int input_delay_ns, int eff_clk, int* dummy_o, int* cycles_remain_o)
{
const int apbclk_kHz = APB_CLK_FREQ/1000;
//calculate how many apb clocks a period has
const int apbclk_n = APB_CLK_FREQ/eff_clk;
const int gpio_delay_ns = gpio_is_used ? 25 : 0;
//calculate how many apb clocks a period has, the 1 is to compensate in case ``input_delay_ns`` is rounded off.
//calculate how many apb clocks the delay is, the 1 is to compensate in case ``input_delay_ns`` is rounded off.
int apb_period_n = (1 + input_delay_ns + gpio_delay_ns)*apbclk_kHz/1000/1000;
if (apb_period_n < 0) apb_period_n = 0;
int dummy_required = apb_period_n/apbclk_n;
int miso_delay = 0;
@ -406,8 +409,10 @@ int spi_get_freq_limit(bool gpio_is_used, int input_delay_ns)
const int apbclk_kHz = APB_CLK_FREQ/1000;
const int gpio_delay_ns = gpio_is_used ? 25 : 0;
//calculate how many apb clocks a period has, the 1 is to compensate in case ``input_delay_ns`` is rounded off.
//calculate how many apb clocks the delay is, the 1 is to compensate in case ``input_delay_ns`` is rounded off.
int apb_period_n = (1 + input_delay_ns + gpio_delay_ns)*apbclk_kHz/1000/1000;
if (apb_period_n < 0) apb_period_n = 0;
return APB_CLK_FREQ/(apb_period_n+1);
}