/**
* @brief Compute UxBRG and set BRGH if needed.
*
* @param[in] uart_num
* @param[in] baudrate
* @return -1 if the baudrate error is greater than 3%, 0 otherwise
*/
static int compute_divisor(unsigned int uart_num, uint32_t baudrate)
{
uint32_t divisor0, divisor1;
uint32_t baudrate0, baudrate1;
uint32_t error0, error1;
int use_brgh = 0;
const uint32_t pclk = mcu_get_system_clock() >> 1;
/* Compute divisor with BRGH=0 */
divisor0 = (pclk / (16 * baudrate)) - 1;
if (divisor0 > UINT16_MAX)
divisor0 = UINT16_MAX;
/* Compute divisor with BRGH=1 */
divisor1 = (pclk / (4 * baudrate)) - 1;
if (divisor1 > UINT16_MAX)
divisor1 = UINT16_MAX;
/* Compute error */
baudrate0 = pclk / (16 * (divisor0 + 1));
baudrate1 = pclk / (4 * (divisor1 + 1));
if (baudrate > baudrate0)
error0 = baudrate - baudrate0;
else
error0 = baudrate0 - baudrate;
if (baudrate > baudrate1)
error1 = baudrate - baudrate1;
else
error1 = baudrate1 - baudrate;
use_brgh = error1 < error0;
/* Check if error is less than 3%. This uses the fact that 1/32 ~ 3% */
if (use_brgh) {
if ((error1 << 5) >= baudrate)
return -1;
} else if ((error0 << 5) >= baudrate) {
return -1;
}
/* Configure UART module */
if (use_brgh) {
UxMODE(uart_num) |= _U1MODE_BRGH_MASK;
UxBRG(uart_num) = divisor1;
} else {
UxBRG(uart_num) = divisor0;
}
return 0;
}
int uart_init(uart_t uart, uint32_t baudrate, uart_rx_cb_t rx_cb, void *arg)
{
assert(uart <= UART_NUMOF && uart != 0); /*No uart 0 on pic32*/
/* Pin Mux should be setup in board file */
pic_uart[uart].regs =
(volatile uint32_t *)(_UART1_BASE_ADDRESS + (uart - 1) * REGS_SPACING);
pic_uart[uart].clock = PERIPHERAL_CLOCK;
UxBRG(pic_uart[uart])= (pic_uart[uart].clock / (16 * baudrate)) - 1;
UxSTA(pic_uart[uart])= 0;
UxMODE(pic_uart[uart])= _U1MODE_ON_MASK;
UxSTASET(pic_uart[uart])= _U1STA_URXEN_MASK;
UxSTASET(pic_uart[uart])= _U1STA_UTXEN_MASK;
return 0;
}