Setup/background
- MIMXRT1021CAG4A on custom PCB similar to MIMXRT1020-EVK
- Trying to establish I2C communication between LPI2C4 acting as a master and a slave device with address 0x6E
My project and my code
I started by clicking “Create a new C/C++ project” in the Quickstart panel and then selecting “evkmimxrt1020” as my SDK.
I also made sure to include the LPI2C driver (version 2.4.1) in my project by selecting i2c on the Drivers tab.
I configured my pins as follows:
And then clicked Project Explorer > Open Peripherals and added a new LPI2C peripheral. I used the default settings except I changed the Peripheral from LPI2C1 to LPI2C4 and I changed the slave address to 0x6E.
I then wrote the following code:
/*
*/
#include <stdio.h>
#include "board.h"
#include "peripherals.h"
#include "pin_mux.h"
#include "clock_config.h"
#include "MIMXRT1021.h"
#include "fsl_debug_console.h"
#include "fsl_lpi2c.h"
/* Defines */
#define BUFFER_SIZE 1
/* Variables */
lpi2c_master_config_t masterConfig;
uint8_t status;
status_t result = kStatus_Success;
uint8_t txBuff[BUFFER_SIZE];
int main(void) {
/* Init board hardware. */
BOARD_ConfigMPU();
BOARD_InitBootPins();
BOARD_InitBootClocks();
BOARD_InitBootPeripherals();
#ifndef BOARD_INIT_DEBUG_CONSOLE_PERIPHERAL
/* Init FSL debug console. */
BOARD_InitDebugConsole();
#endif
PRINTF("MCP3424 Utility\n");
/* Gets the default configuration for master. */
LPI2C_MasterGetDefaultConfig(&masterConfig);
/* Initializes the I2C master. */
//LPI2C_MasterInit(base, masterConfig, sourceClock_Hz);
LPI2C_MasterInit(LPI2C4_PERIPHERAL, &masterConfig, LPI2C4_CLOCK_FREQ);
/* Sends a start and a slave address. */
//LPI2C_MasterStart(base, address, dir);
LPI2C_MasterStart(LPI2C4_PERIPHERAL, LPI2C4_MASTER_SLAVE_ADDRESS, kLPI2C_Write/kLPI2C_Read);
/* Force the counter to be placed into memory. */
volatile static int i = 0 ;
/* Enter an infinite loop, just incrementing a counter. */
while(1) {
i++ ;
/* 'Dummy' NOP to allow source level single stepping of
tight while() loop */
__asm volatile ("nop");
}
return 0 ;
}
Issue
I realize the code is not finished but shouldn’t LPI2C_MasterStart at least send the slave address? I thought so but when I run the code my scope shows nothing on the SDA line (it never goes low). I do see a 100 kHz clock signal on the SCL line however.
When calling LPI2C_MasterInit, I changed &masterConfig to &LPI2C4_masterConfig and now it appears the start condition is being transmitted on SDL.
Yellow: SDL
Violet: SCL
However the slave address is still not being transmitted. I checked the return value of LPI2C_MasterStart and it is 0.
