TM4C1294 connected with SPI to 23LC1024 SRAM

Daniel Norris

I'm back with another SPI question.

I am still using the TM4C1294 development board, but this time I am trying to get an external SPI SRAM chip to work. The SRAM being used is a Microchip brand 23LC1024.

The issue I am having is that the SRAM chip is not sending data back to me under any circumstance. I am not sure if my issue is code or hardware at this point because both seem to follow what I can find every where else on the web. Code and Connections below. I use an oscilloscope on all four lines and I see exactly what i expect sent to the SRAM but that is all.

Any help is appreciated as I am stuck.

Connections to 23LC1024:

Pin 1: CS: Pulled up through 10k resistor, connected to PQ1 on board

Pin2: SO: connected to PQ3

Pin3: connected to 3.3V

Pin4: Vss: connect to ground

Pin5: SI: Connected to PQ2

Pin6: SCK: connected to PQ0

Pin7: connected to Vss Vcc

Pin8: Vss: connected to 3.3V (Edit as Pointed out by Amit)

Pin8: Vcc: connected to 3.3V

Fullscreen 8304.main.c Download

//*****************************************************************************
//
// spi_master.c - Example demonstrating how to configure SSI0 in SPI master
//                mode.
//
// Copyright (c) 2010-2015 Texas Instruments Incorporated.  All rights reserved.
// Software License Agreement
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//
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//   notice, this list of conditions and the following disclaimer.
//
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//   distribution.
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//
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
// (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 2.1.1.71 of the Tiva Firmware Development Package.
//
//*****************************************************************************

#include <stdbool.h>
#include <stdint.h>
#include <string.h>
#include <math.h>
#include "inc/hw_memmap.h"
#include "driverlib/gpio.h"
#include "driverlib/pin_map.h"
#include "driverlib/ssi.h"
#include "driverlib/sysctl.h"
#include "driverlib/uart.h"
#include "utils/ustdlib.h"
#include "utils/uartstdio.h"

//*****************************************************************************
//
// 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 SSI0 in master Freescale (SPI) 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 junk = 0;
    uint32_t pui32DataRx  = 0;

    //
    // 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), 120000000);
#else
    SysCtlClockSet(SYSCTL_SYSDIV_1 | SYSCTL_USE_OSC | SYSCTL_OSC_MAIN |
                   SYSCTL_XTAL_16MHZ);
#endif

    //
    // Set up the serial console to use for displaying messages.  This is
    // just for this example program and is not needed for SSI operation.
    //
    InitConsole();

    //
    // Display the setup on the console.
    //
    UARTprintf("\033[2J\033[H");
    UARTprintf("SSI ->\n");
    UARTprintf("  Mode: SPI\n");
    UARTprintf("  Data: 16-bit\n\n");

    //
    // The SSI0 peripheral must be enabled for use.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_SSI3);

    //
    // For this example SSI0 is used with PortA[5:2].  The actual port and pins
    // used may be different on your part, consult the data sheet for more
    // information.  GPIO port A needs to be enabled so these pins can be used.
    // TODO: change this to whichever GPIO port you are using.
    //
    SysCtlPeripheralEnable(SYSCTL_PERIPH_GPIOQ);

    //
    // Configure the pin muxing for SSI0 functions on port A2, A3, A4, and A5.
    // 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_PQ0_SSI3CLK);
    GPIOPinTypeGPIOOutput(GPIO_PORTQ_BASE, GPIO_PIN_1); //CS
    GPIOPinConfigure(GPIO_PQ3_SSI3XDAT1);
    GPIOPinConfigure(GPIO_PQ2_SSI3XDAT0);

    //
    // Configure the GPIO settings for the SSI pins.  This function also gives
    // control of these pins to the SSI hardware.  Consult the data sheet to
    // see which functions are allocated per pin.
    // The pins are assigned as follows:
    //      PQ2 - SSI0Tx
    //      PQ3 - SSI0Rx
    //      PQ1 - SSI0Fss
    //      PQ0 - SSI0CLK
    // TODO: change this to select the port/pin you are using.
    //
    GPIOPinTypeSSI(GPIO_PORTQ_BASE, GPIO_PIN_0 | /*GPIO_PIN_1 |*/ GPIO_PIN_2 | GPIO_PIN_3);

    //
    // Configure and enable the SSI port for SPI master mode.  Use SSI0,
    // system clock supply, idle clock level low and active low clock in
    // freescale SPI mode, master mode, 1MHz SSI frequency, and 8-bit data.
    // For SPI mode, you can set the polarity of the SSI clock when the SSI
    // unit is idle.  You can also configure what clock edge you want to
    // capture data on.  Please reference the datasheet for more information on
    // the different SPI modes.
    //
#if defined(TARGET_IS_TM4C129_RA0) ||                                         \
	defined(TARGET_IS_TM4C129_RA1) ||                                         \
    defined(TARGET_IS_TM4C129_RA2)
    SSIConfigSetExpClk(SSI3_BASE, ui32SysClock, SSI_FRF_MOTO_MODE_1,
                       SSI_MODE_MASTER, 10000000, 8);
#else
    SSIConfigSetExpClk(SSI3_BASE, SysCtlClockGet(), SSI_FRF_MOTO_MODE_0,
                       SSI_MODE_MASTER, 1000000, 32);
#endif

    //
    // Enable the SSI0 module.
    //
    SSIEnable(SSI3_BASE);

    //
    // Read any residual data from the SSI port.  This makes sure the receive
    // FIFOs are empty, so we don't read any unwanted junk.  This is done here
    // because the SPI SSI mode is full-duplex, which allows you to send and
    // receive at the same time.  The SSIDataGetNonBlocking function returns
    // "true" when data was returned, and "false" when no data was returned.
    // The "non-blocking" function checks if there is any data in the receive
    // FIFO and does not "hang" if there isn't.
    //
    while(SSIDataGetNonBlocking(SSI3_BASE, &pui32DataRx))
    {
    }

    uint32_t Reset = 0xff;           //0b 1111 1111
    uint32_t write = 0x01;
    uint32_t write_2 = 0x40;
    uint32_t read = 0x05;

	GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, GPIO_PIN_1);
	SysCtlDelay(ui32SysClock / (10) );

	GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, 0);
//	SSIDataPut(SSI3_BASE, Reset);
	SSIDataPut(SSI3_BASE, write);                          //write to write mode register 0x01
	SSIDataPut(SSI3_BASE, write_2);						   //Write the mode 0x40
	SSIDataGet(SSI3_BASE, &junk);						   //Junk reads
	SSIDataGet(SSI3_BASE, &junk);
//	SSIDataGet(SSI3_BASE, &junk);
	GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, GPIO_PIN_1);

	GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, 0);
	SSIDataPut(SSI3_BASE, read);							//write to read mode register 0x05
	SSIDataPut(SSI3_BASE, 0x00);							//Junk write
	SSIDataGet(SSI3_BASE, &junk);							//Junk read, watching osciloscope for responces
	SSIDataGet(SSI3_BASE, &junk);
	GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, GPIO_PIN_1);
	SysCtlDelay(ui32SysClock / (10) );


	while(1)
	{

		//test write to the RAM at memory location 0x000002
		GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, 0);
		SSIDataPut(SSI3_BASE, 0x02);
		SSIDataPut(SSI3_BASE, 0x00);
		SSIDataPut(SSI3_BASE, 0x00);
		SSIDataPut(SSI3_BASE, 0x02);
		SSIDataPut(SSI3_BASE, 0x44);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, GPIO_PIN_1);

		//test read from RAM at memory location 0x000002
		GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, 0);
		SSIDataPut(SSI3_BASE, 0x03);
		SSIDataPut(SSI3_BASE, 0x00);
		SSIDataPut(SSI3_BASE, 0x00);
		SSIDataPut(SSI3_BASE, 0x02);
		SSIDataPut(SSI3_BASE, 0x00);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		SSIDataGet(SSI3_BASE, &junk);
		GPIOPinWrite(GPIO_PORTQ_BASE, GPIO_PIN_1, GPIO_PIN_1);

		//See results on osciloscope but in the event that the string is to long catch it in UART as well
		int i;
		for(i = 0; i < 1; i++)
		{
			UARTprintf("%x", junk);
		}
		UARTprintf("\n");
	}

}

over 9 years ago

0 Amit Ashara over 9 years ago

TI__Guru**** 244400 points

Hello Daniel

"Pin8: Vss: connected to 3.3V" VSS is GND. Can you confirm one more time your connections between the TM4C and the serial SRAM?

0 Daniel Norris over 9 years ago in reply to Amit Ashara

Prodigy 180 points

Yep sorry that is a typo, Pin 8 is Vcc and is connected to 3.3V. All other connections are the same as listed in my original post and I will edit the original post to reflect the correction you pointed out.

0 Amit Ashara over 9 years ago in reply to Daniel Norris

TI__Guru**** 244400 points

Hello Daniel,

Can you please post a single write and read to the SRAM with an oscilloscope trace,

0 Daniel Norris over 9 years ago in reply to Amit Ashara

Prodigy 180 points

Hello Amit,

Assuming I understood you correctly, attached are two images. The first is the write sequence from the while loop and the second is the read sequence from the while loop.

Write:

Read:

Thank you for the speed of responses.

0 Amit Ashara over 9 years ago in reply to Daniel Norris

TI__Guru**** 244400 points

Hello Daniel,

What mode has been selected for SSI. As per the timing the SI must be sampled at the rising edge, but as per the waveform it seems that the SI is being sent after the rising edge of the clock.

0 Daniel Norris over 9 years ago in reply to Amit Ashara

Prodigy 180 points

Hello Amit,

The code I have is:
SSIConfigSetExpClk(SSI3_BASE, ui32SysClock, SSI_FRF_MOTO_MODE_1, SSI_MODE_MASTER, 100000, 8);

So If I understand your question I am using, SSI_FRF_MOTO_MODE_1. Which I thought set the clock for rising edge triggers, but my understanding of phase may be wrong.

0 Daniel Norris over 9 years ago in reply to Amit Ashara

Prodigy 180 points

Hello Amit

It would appear my understanding of phase is wrong and that I should instead be using SSI_FRF_MOTO_MODE_0. I had tried it before, but apparently had other issues in the code at that point.
Thank you for the help, it is greatly appreciated.

0 Amit Ashara over 9 years ago in reply to Daniel Norris

TI__Guru**** 244400 points

Hello Daniel,

Did it work after making the changes?

0 Daniel Norris over 9 years ago in reply to Amit Ashara

Prodigy 180 points

Hello Amit,

Yes changing SSI_FRF_MOTO_MODE_1 to SSI_FRF_MOTO_MODE_0 made it so I saw communication over the SO line.

Thank you for your help.

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TM4C1294 connected with SPI to 23LC1024 SRAM