Tool/software:
I am having trouble seeing the I2C SDA and SCL signals on my EK-TM4C123GXL Launchpad using example code.
I have pins PB2 on CH1 and PB3 on CH2.
Both PB2 and PB3 are connected to 1.5k pull up resistors.
Below is the code I am using,
//*****************************************************************************
//
// master_slave_loopback.c - Example demonstrating a simple I2C message
// transmission and reception.
//
// Copyright (c) 2010-2020 Texas Instruments Incorporated. All rights reserved.
// Software License Agreement
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
//
// Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
//
// Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in the
// documentation and/or other materials provided with the
// distribution.
//
// Neither the name of Texas Instruments Incorporated nor the names of
// its contributors may be used to endorse or promote products derived
// from this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
//
// This is part of revision 2.2.0.295 of the Tiva Firmware Development Package.
//
//*****************************************************************************
#include <stdbool.h>
#include <stdint.h>
#include "inc/hw_i2c.h"
#include "inc/hw_memmap.h"
#include "inc/hw_types.h"
#include "driverlib/gpio.h"
#include "driverlib/i2c.h"
#include "driverlib/pin_map.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/uartstdio.h"
//*****************************************************************************
//
//! \addtogroup i2c_examples_list
//! <h1>I2C Master Loopback (i2c_master_slave_loopback)</h1>
//!
//! This example shows how to configure the I2C0 module for loopback mode.
//! This includes setting up the master and slave module. Loopback mode
//! internally connects the master and slave data and clock lines together.
//! The address of the slave module is set in order to read data from the
//! master. Then the data is checked to make sure the received data matches
//! the data that was transmitted. This example uses a polling method for
//! sending and receiving data.
//!
//! This example uses the following peripherals and I/O signals. You must
//! review these and change as needed for your own board:
//! - I2C0 peripheral
//! - GPIO Port B peripheral (for I2C0 pins)
//! - I2C0SCL - PB2
//! - I2C0SDA - PB3
//!
//! The following UART signals are configured only for displaying console
//! messages for this example. These are not required for operation of I2C.
//! - UART0 peripheral
//! - GPIO Port A peripheral (for UART0 pins)
//! - UART0RX - PA0
//! - UART0TX - PA1
//!
//! This example uses the following interrupt handlers. To use this example
//! in your own application you must add these interrupt handlers to your
//! vector table.
//! - None.
//
//*****************************************************************************
//*****************************************************************************
//
// Number of I2C data packets to send.
//
//*****************************************************************************
#define NUM_I2C_DATA 3
//*****************************************************************************
//
// Set the address for slave module. This is a 7-bit address sent in the
// following format:
// [A6:A5:A4:A3:A2:A1:A0:RS]
//
// A zero in the "RS" position of the first byte means that the master
// transmits (sends) data to the selected slave, and a one in this position
// means that the master receives data from the slave.
//
//*****************************************************************************
#define SLAVE_ADDRESS 0x3C
//*****************************************************************************
//
// This function sets up UART0 to be used for a console to display information
// as the example is running.
//
//*****************************************************************************
void
InitConsole(void)
{
//
// Enable GPIO port A which is used for UART0 pins.
// TODO: change this to whichever GPIO port you are using.
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOA);
//
// Configure the pin muxing for UART0 functions on port A0 and A1.
// This step is not necessary if your part does not support pin muxing.
// TODO: change this to select the port/pin you are using.
//
GPIOPinConfigure(GPIO_PA0_U0RX);
GPIOPinConfigure(GPIO_PA1_U0TX);
//
// Enable UART0 so that we can configure the clock.
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_UART0);
//
// Use the internal 16MHz oscillator as the UART clock source.
//
UARTClockSourceSet(UART0_BASE, UART_CLOCK_PIOSC);
//
// Select the alternate (UART) function for these pins.
// TODO: change this to select the port/pin you are using.
//
GPIOPinTypeUART(GPIO_PORTA_BASE, GPIO_PIN_0 | GPIO_PIN_1);
//
// Initialize the UART for console I/O.
//
UARTStdioConfig(0, 115200, 16000000);
}
//*****************************************************************************
//
// Configure the I2C0 master and slave and connect them using loopback mode.
//
//*****************************************************************************
int
main(void)
{
#if defined(TARGET_IS_TM4C129_RA0) || \
defined(TARGET_IS_TM4C129_RA1) || \
defined(TARGET_IS_TM4C129_RA2)
uint32_t ui32SysClock;
#endif
uint32_t pui32DataTx[NUM_I2C_DATA];
uint32_t pui32DataRx[NUM_I2C_DATA];
uint32_t ui32Index;
//
// Set the clocking to run directly from the external crystal/oscillator.
// TODO: The SYSCTL_XTAL_ value must be changed to match the value of the
// crystal on your board.
//
#if defined(TARGET_IS_TM4C129_RA0) || \
defined(TARGET_IS_TM4C129_RA1) || \
defined(TARGET_IS_TM4C129_RA2)
ui32SysClock = SysCtlClockFreqSet((SYSCTL_XTAL_25MHZ |
SYSCTL_OSC_MAIN |
SYSCTL_USE_OSC), 25000000);
#else
SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
SYSCTL_XTAL_16MHZ);
#endif
//
// The I2C0 peripheral must be enabled before use.
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_I2C0);
//
// For this example I2C0 is used with PortB[3:2]. The actual port and
// pins used may be different on your part, consult the data sheet for
// more information. GPIO port B needs to be enabled so these pins can
// be used.
// TODO: change this to whichever GPIO port you are using.
//
SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOB);
//
// Configure the pin muxing for I2C0 functions on port B2 and B3.
// This step is not necessary if your part does not support pin muxing.
// TODO: change this to select the port/pin you are using.
//
GPIOPinConfigure(GPIO_PB2_I2C0SCL);
GPIOPinConfigure(GPIO_PB3_I2C0SDA);
//
// Select the I2C function for these pins. This function will also
// configure the GPIO pins pins for I2C operation, setting them to
// open-drain operation with weak pull-ups. Consult the data sheet
// to see which functions are allocated per pin.
// TODO: change this to select the port/pin you are using.
//
GPIOPinTypeI2CSCL(GPIO_PORTB_BASE, GPIO_PIN_2);
GPIOPinTypeI2C(GPIO_PORTB_BASE, GPIO_PIN_3);
//
// Enable loopback mode. Loopback mode is a built in feature that is
// useful for debugging I2C operations. It internally connects the I2C
// master and slave terminals, which effectively let's you send data as
// a master and receive data as a slave.
// NOTE: For external I2C operation you will need to use external pullups
// that are stronger than the internal pullups. Refer to the datasheet for
// more information.
//
//I2CLoopbackEnable(I2C0_BASE);
//
// Enable and initialize the I2C0 master module. Use the system clock for
// the I2C0 module. The last parameter sets the I2C data transfer rate.
// If false the data rate is set to 100kbps and if true the data rate will
// be set to 400kbps. For this example we will use a data rate of 100kbps.
//
#if defined(TARGET_IS_TM4C129_RA0) || \
defined(TARGET_IS_TM4C129_RA1) || \
defined(TARGET_IS_TM4C129_RA2)
I2CMasterInitExpClk(I2C0_BASE, ui32SysClock, false);
#else
I2CMasterInitExpClk(I2C0_BASE, SysCtlClockGet(), false);
#endif
//
// Enable the I2C0 slave module. This module is enabled only for testing
// purposes. It does not need to be enabled for proper operation of the
// I2Cx master module.
//
I2CSlaveEnable(I2C0_BASE);
//
// Set the slave address to SLAVE_ADDRESS. In loopback mode, it's an
// arbitrary 7-bit number (set in a macro above) that is sent to the
// I2CMasterSlaveAddrSet function.
//
I2CSlaveInit(I2C0_BASE, SLAVE_ADDRESS);
//
// Tell the master module what address it will place on the bus when
// communicating with the slave. Set the address to SLAVE_ADDRESS
// (as set in the slave module). The receive parameter is set to false
// which indicates the I2C Master is initiating a writes to the slave. If
// true, that would indicate that the I2C Master is initiating reads from
// the slave.
//
I2CMasterSlaveAddrSet(I2C0_BASE, SLAVE_ADDRESS, false);
//
// Set up the serial console to use for displaying messages. This is
// just for this example program and is not needed for I2C operation.
//
InitConsole();
//
// Display the example setup on the console.
//
UARTprintf("I2C Loopback Example ->");
UARTprintf("\n Module = I2C0");
UARTprintf("\n Mode = Single Send/Receive");
UARTprintf("\n Rate = 100kbps\n\n");
//
// Initalize the data to send.
//
pui32DataTx[0] = 'I';
pui32DataTx[1] = '2';
pui32DataTx[2] = 'C';
//
// Initalize the receive buffer.
//
for(ui32Index = 0; ui32Index < NUM_I2C_DATA; ui32Index++)
{
pui32DataRx[ui32Index] = 0;
}
//
// Indicate the direction of the data.
//
UARTprintf("Tranferring from: Master -> Slave\n");
//
// Send 3 peices of I2C data from the master to the slave.
//
for(;;)
{
for(ui32Index = 0; ui32Index < NUM_I2C_DATA; ui32Index++)
{
//
// Display the data that the I2C0 master is transferring.
//
UARTprintf(" Sending: '%c' . . . ", pui32DataTx[ui32Index]);
//
// Place the data to be sent in the data register
//
I2CMasterDataPut(I2C0_BASE, pui32DataTx[ui32Index]);
//
// Initiate send of data from the master. Since the loopback
// mode is enabled, the master and slave units are connected
// allowing us to receive the same data that we sent out.
//
I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_SINGLE_SEND);
//
// Wait until the slave has received and acknowledged the data.
//
//hile(!(I2CSlaveStatus(I2C0_BASE) & I2C_SLAVE_ACT_RREQ))
//{
//}
//
// Read the data from the slave.
//
// pui32DataRx[ui32Index] = I2CSlaveDataGet(I2C0_BASE);
//
// Wait until master module is done transferring.
//
while(I2CMasterBusy(I2C0_BASE))
{
}
//
// Display the data that the slave has received.
//
//UARTprintf("Received: '%c'\n", pui32DataRx[ui32Index]);
}
}
//
// Reset receive buffer.
//
for(ui32Index = 0; ui32Index < NUM_I2C_DATA; ui32Index++)
{
pui32DataRx[ui32Index] = 0;
}
//
// Indicate the direction of the data.
//
UARTprintf("\n\nTranferring from: Slave -> Master\n");
//
// Modifiy the data direction to true, so that seeing the address will
// indicate that the I2C Master is initiating a read from the slave.
//
I2CMasterSlaveAddrSet(I2C0_BASE, SLAVE_ADDRESS, true);
//
// Do a dummy receive to make sure you don't get junk on the first receive.
//
I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_SINGLE_RECEIVE);
//
// Dummy acknowledge and wait for the receive request from the master.
// This is done to clear any flags that should not be set.
//
while(!(I2CSlaveStatus(I2C0_BASE) & I2C_SLAVE_ACT_TREQ))
{
}
for(ui32Index = 0; ui32Index < NUM_I2C_DATA; ui32Index++)
{
//
// Display the data that I2C0 slave module is transferring.
//
UARTprintf(" Sending: '%c' . . . ", pui32DataTx[ui32Index]);
//
// Place the data to be sent in the data register
//
I2CSlaveDataPut(I2C0_BASE, pui32DataTx[ui32Index]);
//
// Tell the master to read data.
//
I2CMasterControl(I2C0_BASE, I2C_MASTER_CMD_SINGLE_RECEIVE);
//
// Wait until the slave is done sending data.
//
while(!(I2CSlaveStatus(I2C0_BASE) & I2C_SLAVE_ACT_TREQ))
{
}
//
// Read the data from the master.
//
pui32DataRx[ui32Index] = I2CMasterDataGet(I2C0_BASE);
//
// Display the data that the slave has received.
//
UARTprintf("Received: '%c'\n", pui32DataRx[ui32Index]);
}
//
// Tell the user that the test is done.
//
UARTprintf("\nDone.\n\n");
//
// Return no errors
//
return(0);
}
Both CH1 and CH2 both stay at 3.3V constantly even when sending "I2C" constantly.
Thanks,
Allan
