Kinetis MicrocontrollersのトピックRe: LPUART0 FRDM K82F

LPUART0 FRDM K82F

akimata — Sun, 06 May 2018 12:47:52 GMT

Hello i've been trying to send some informations throught UART for some time but i can't get it to work, i'm probably missing something. The problem is that if i check with logic analyzer my TX line i can clearly see that data is correct but in realterm or any other software connected through USB-TTL only what i get is null(00).

Here is my simple code:

#include <stdio.h>
#include "board.h"
#include "peripherals.h"
#include "pin_mux.h"
#include "clock_config.h"
#include "MK82F25615.h"

uint16_t sbr;
int main(void) {
/* Init board hardware. */
BOARD_InitBootPins();
BOARD_InitBootClocks();
BOARD_InitBootPeripherals();
/* Init FSL debug console. */
BOARD_InitDebugConsole();
SIM -> CLKDIV1 &= ~SIM_CLKDIV1_OUTDIV1_MASK;
SIM -> CLKDIV1 &= ~SIM_CLKDIV1_OUTDIV2_MASK;
SIM -> SCGC5 |= SIM_SCGC5_PORTB_MASK;
SIM -> SCGC2 |= SIM_SCGC2_LPUART0_MASK;
SIM -> SOPT2 |= SIM_SOPT2_LPUARTSRC(0x01);
MCG -> C6 &= ~ MCG_C6_PLLS_MASK;
MCG -> C4 |= MCG_C4_DMX32_MASK;
MCG -> C4 |= MCG_C4_DRST_DRS(0);
PORTB-> PCR[16] = PORT_PCR_MUX(0x03);
PORTB-> PCR[17] = PORT_PCR_MUX(0x03);
LPUART0 -> CTRL &= ~LPUART_CTRL_TE_MASK;
LPUART0 -> CTRL &= ~LPUART_CTRL_RE_MASK;
LPUART0 -> BAUD |=LPUART_BAUD_OSR(15);
sbr = (23986176/(16*9600));
LPUART0 -> BAUD |= LPUART_BAUD_SBR(sbr);
LPUART0 -> CTRL &= ~LPUART_CTRL_M_MASK;
LPUART0 -> CTRL &= ~LPUART_CTRL_PE_MASK;
LPUART0 -> BAUD &= ~LPUART_BAUD_SBNS_MASK;
LPUART0 -> CTRL |= LPUART_CTRL_TE_MASK;
LPUART0 -> CTRL |= LPUART_CTRL_RE_MASK;
while(1)
{
LPUART0 -> CTRL |= LPUART_CTRL_TE_MASK;
LPUART0 -> DATA = 0x53;
while(!(LPUART0 -> STAT & LPUART_STAT_TC_MASK) );
LPUART0 -> CTRL &= ~LPUART_CTRL_TE_MASK;
}
return 0 ;
}

Any ideas? i'm suspecting baudrate but i have no idea what could be wrong in calculations.

Re: LPUART0 FRDM K82F

mjbcswitzerland — Mon, 07 May 2018 20:17:35 GMT

Hi Rufus

What baud rate do you measure?
Is 23986176 the PLL/FLL speed that you really have?

For more exact 9600 Baud calculation use:
(((LPUART_CLOCK/8/9600) + 1)/2)

Regards

Mark

uTasker developer and supporter (+5'000 hours experience on +60 Kinetis derivatives in +80 product developments)
Kinetis: http://www.utasker.com/kinetis.html

Re: LPUART0 FRDM K82F

akimata — Tue, 08 May 2018 05:21:16 GMT

According to MCG_C4 with 32.768kHz reference mutiplied by FLL Factor 732 i receive 23986176.

I switched to internal fast clock 4Mhz and transmission seems to be working but the data i put do the register it's not what i receive on my PC so it seems like the baudrate is still off with new formula.

I used this to switch for internal fast clock:

MCG -> SC &= ~MCG_SC_FCRDIV_MASK;
MCG -> C1 |=MCG_C1_IRCLKEN_MASK |MCG_C1_IREFSTEN_MASK;
MCG -> C2 |=MCG_C2_IRCS_MASK;
SIM -> SCGC5 |= SIM_SCGC5_PORTB_MASK;
SIM -> SCGC2 |= SIM_SCGC2_LPUART0_MASK;
SIM -> SOPT2 |= SIM_SOPT2_LPUARTSRC(3);

Re: LPUART0 FRDM K82F

mjbcswitzerland — Tue, 08 May 2018 14:40:58 GMT

Grzegorz

You really need to "measure" the Baud rate - if it is off by a certain factor knowing it will help you identify why.

Regards

Mark

Re: LPUART0 FRDM K82F

akimata — Wed, 18 Jul 2018 13:36:24 GMT

Changing oversampling ratio solved the baudrate problem. How oversampling affects TX side?