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nrf/uart: Use formula instead of switch for baudrate calculation.

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This saves a bit of code:
nrf51: -176
nrf52: -152
This commit is contained in:
Ayke van Laethem 2018-08-02 13:46:18 +02:00 committed by Damien George
parent 2f5d113fad
commit a293fa3d6d
1 changed files with 14 additions and 47 deletions
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61
ports/nrf/modules/machine/uart.c
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@ -170,55 +170,22 @@ STATIC mp_obj_t machine_hard_uart_make_new(const mp_obj_type_t *type, size_t n_a
config.interrupt_priority = 6;
#endif
switch (args[ARG_baudrate].u_int) {
case 1200:
config.baudrate = NRF_UART_BAUDRATE_1200;
break;
case 2400:
config.baudrate = NRF_UART_BAUDRATE_2400;
break;
case 4800:
config.baudrate = NRF_UART_BAUDRATE_4800;
break;
case 9600:
config.baudrate = NRF_UART_BAUDRATE_9600;
break;
case 14400:
config.baudrate = NRF_UART_BAUDRATE_14400;
break;
case 19200:
config.baudrate = NRF_UART_BAUDRATE_19200;
break;
case 28800:
config.baudrate = NRF_UART_BAUDRATE_28800;
break;
case 38400:
config.baudrate = NRF_UART_BAUDRATE_38400;
break;
case 57600:
config.baudrate = NRF_UART_BAUDRATE_57600;
break;
case 76800:
config.baudrate = NRF_UART_BAUDRATE_76800;
break;
case 115200:
config.baudrate = NRF_UART_BAUDRATE_115200;
break;
case 230400:
config.baudrate = NRF_UART_BAUDRATE_230400;
break;
case 250000:
config.baudrate = NRF_UART_BAUDRATE_250000;
break;
case 1000000:
config.baudrate = NRF_UART_BAUDRATE_1000000;
break;
default:
nlr_raise(mp_obj_new_exception_msg_varg(&mp_type_ValueError,
"UART baudrate not supported, %u", args[ARG_baudrate].u_int));
break;
// These baudrates are not supported, it seems.
if (args[ARG_baudrate].u_int < 1200 || args[ARG_baudrate].u_int > 1000000) {
mp_raise_ValueError("UART baudrate not supported");
}
// Magic: calculate 'baudrate' register from the input number.
// Every value listed in the datasheet will be converted to the
// correct register value, except for 192600. I believe the value
// listed in the nrf52 datasheet (0x0EBED000) is incorrectly rounded
// and should be 0x0EBEE000, as the nrf51 datasheet lists the
// nonrounded value 0x0EBEDFA4.
// Some background:
// https://devzone.nordicsemi.com/f/nordic-q-a/391/uart-baudrate-register-values/2046#2046
config.baudrate = args[ARG_baudrate].u_int / 400 * (uint32_t)(400ULL * (uint64_t)UINT32_MAX / 16000000ULL);
config.baudrate = (config.baudrate + 0x800) & 0xffffff000; // rounding
config.pseltxd = MICROPY_HW_UART1_TX;
config.pselrxd = MICROPY_HW_UART1_RX;