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Compute fp on the fly

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This commit is contained in:
Philippe Teuwen
2019-05-18 22:20:47 +02:00
parent ec796f4d81
commit b17da830ed
1 changed files with 4 additions and 6 deletions
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10
common/usart.c
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@@ -236,13 +236,11 @@ void usart_init(uint32_t baudrate, uint8_t parity) {
// OVER = 1, -yes we are oversampling // OVER = 1, -yes we are oversampling
// baudrate == selected clock/8/CD --> this is ours // baudrate == selected clock/8/CD --> this is ours
// //
uint32_t fractional = 0;
if ( baudrate == 921600 )
fractional = 4;
else if ( baudrate == 1382400 )
fractional = 2;
uint32_t brgr = 48000000 / (usart_baudrate << 3); uint32_t brgr = 48000000 / (usart_baudrate << 3);
pUS1->US_BRGR = (fractional << 16) | brgr; // doing fp = round((mck / (usart_baudrate << 3) - brgr) * 8) with integers:
uint32_t fp = ((16 * 48000000 / (usart_baudrate << 3) - 16 * brgr)+1)/2;
pUS1->US_BRGR = (fp << 16) | brgr;
// Write the Timeguard Register // Write the Timeguard Register
pUS1->US_TTGR = 0; pUS1->US_TTGR = 0;