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Enable custom UART baudrate for nRF52 #712

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Merged
hathach merged 4 commits into from
May 12, 2026
Merged

Enable custom UART baudrate for nRF52 #712

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d410cd7
Enable custom UART baudrate for nRF52
Jan 8, 2022
5e92a1f
Fix the compilation error
Jan 8, 2022
73a0e86
Merge branch 'master' into fork/deepindeep/variable_baudrate_iso
hathach May 11, 2026
45103a9
update UART to use pre-computed baudrate values for standard rates wi…
hathach May 11, 2026
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64 changes: 28 additions & 36 deletions cores/nRF5/Uart.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -90,42 +90,34 @@ void Uart::begin(unsigned long baudrate, uint16_t config)

uint32_t nrfBaudRate;

if (baudrate <= 1200) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud1200;
} else if (baudrate <= 2400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud2400;
} else if (baudrate <= 4800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud4800;
} else if (baudrate <= 9600) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud9600;
} else if (baudrate <= 14400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud14400;
} else if (baudrate <= 19200) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud19200;
} else if (baudrate <= 28800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud28800;
} else if (baudrate <= 31250) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud31250;
} else if (baudrate <= 38400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud38400;
} else if (baudrate <= 56000) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud56000;
} else if (baudrate <= 57600) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud57600;
} else if (baudrate <= 76800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud76800;
} else if (baudrate <= 115200) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud115200;
} else if (baudrate <= 230400) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud230400;
} else if (baudrate <= 250000) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud250000;
} else if (baudrate <= 460800) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud460800;
} else if (baudrate <= 921600) {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud921600;
} else {
nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud1M;
// Use Nordic's pre-computed values for standard baudrates to match other
// nRF devices exactly; fall back to runtime computation for custom values.
switch (baudrate) {
case 1200: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud1200; break;
case 2400: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud2400; break;
case 4800: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud4800; break;
case 9600: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud9600; break;
case 14400: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud14400; break;
case 19200: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud19200; break;
case 28800: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud28800; break;
case 31250: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud31250; break;
case 38400: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud38400; break;
case 56000: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud56000; break;
case 57600: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud57600; break;
case 76800: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud76800; break;
case 115200: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud115200; break;
case 230400: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud230400; break;
case 250000: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud250000; break;
case 460800: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud460800; break;
case 921600: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud921600; break;
case 1000000: nrfBaudRate = UARTE_BAUDRATE_BAUDRATE_Baud1M; break;
default: {
// BAUDRATE = round(baudrate * 2^32 / 16e6) and round to nearest 0x1000.
// https://devzone.nordicsemi.com/f/nordic-q-a/391/uart-baudrate-register-values
const uint32_t regValue = (uint32_t)(((uint64_t)baudrate * 268435456ULL + 500000ULL) / 1000000ULL);
nrfBaudRate = (regValue + 0x800) & 0xFFFFF000;
break;
}
}

nrfUart->BAUDRATE = nrfBaudRate;
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