FaSTTUBe/ams-slave-22
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Trim clock downwards during frequency hopping

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This commit is contained in:
jazzpi
2022-08-04 15:44:46 +02:00
parent 40bbb3d4c0
commit 4f02c21bd9
1 changed files with 14 additions and 13 deletions
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27
Core/Src/ClockSync.c
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@ -70,10 +70,11 @@
* STAGE 1 * STAGE 1
* ------- * -------
* Stage 1 trims the HSI until at least one MASTER_HEARTBEAT frame has been * Stage 1 trims the HSI until at least one MASTER_HEARTBEAT frame has been
* received. The frequency alternates between lower and higher values, i.e. if * received. The frequency first goes down until it reaches 0, then goes up from
* the trim was initially 16, it will go through the following values: * the initial value. I.e. if the trim was initially 5, it will go through the
* following values:
* *
* 16 -> 14 -> 18 -> 12 -> 20 -> 10 -> 22 -> ... * 5 -> 3 -> 1 -> 6 -> 8 -> ...
* *
* Once a MASTER_HEARTBEAT frame has been received, the slave transitions to * Once a MASTER_HEARTBEAT frame has been received, the slave transitions to
* stage 2. * stage 2.
@ -81,7 +82,7 @@
* STAGE 2 * STAGE 2
* ------- * -------
* Stage 2 trims the HSI further until at least three consecutive * Stage 2 trims the HSI further until at least three consecutive
* MASTER_HEARTBEAT frames have been received. The frequency alternates in the * MASTER_HEARTBEAT frames have been received. The frequency is trimmed in the
* same fashion as in stage 1, but now around the frequency where a * same fashion as in stage 1, but now around the frequency where a
* MASTER_HEARTBEAT frame was received in stage 1, and more slowly. * MASTER_HEARTBEAT frame was received in stage 1, and more slowly.
* *
@ -314,15 +315,15 @@ void trim_hsi_by(int32_t delta) {
} }
uint8_t calculate_freq_hopping_trim(uint32_t freq_hopping_iteration) { uint8_t calculate_freq_hopping_trim(uint32_t freq_hopping_iteration) {
int32_t trim_delta = (freq_hopping_iteration + 1) * FREQ_HOPPING_TRIM_STEPS; int32_t trim_delta =
if (freq_hopping_iteration % 2 == 0) { ((freq_hopping_iteration + 1) * FREQ_HOPPING_TRIM_STEPS) %
trim_delta = -trim_delta; (RCC_CR_HSITRIM_MAX + 1);
int32_t new_trim = freq_hopping_start_trim - trim_delta;
if (new_trim < 0) {
// Trim upwards from the start trim
new_trim = trim_delta;
} }
int32_t new_trim = freq_hopping_start_trim + trim_delta; return new_trim;
if (new_trim < 0) {
new_trim += RCC_CR_HSITRIM_MAX + 1;
} else if (new_trim > RCC_CR_HSITRIM_MAX) {
new_trim -= RCC_CR_HSITRIM_MAX + 1;
}
} }