• State Not Answered
  • Locked Locked
  • Replies 3 replies
  • Subscribers 21 subscribers
  • Views 1290 views
  • Users 0 members are here
2025 survey

We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.

Options
Related
How was your experience today?
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

SPI communication between two STR910

E. U.

Hello,

I want to comunicate two STR910 micros via SPI. One of them will be the master, and other the slave. The code is very simple:

[b]MASTER:[/b]

/* CLK, MISO & MOSI configuration */
SCU->GPIOOUT[3] &= 0xC0FF;
SCU->GPIOOUT[3] |= 0x2200;
SCU->GPIOIN[3] |= 0x20;

/* SPI1 configuration */
SSP1->CR0 = 0x0007; /* CPHA=0, CPOL=0 */
SSP1->CR1 = 0x0002; /* Master mode & SSP Enable */
SSP1->PR = 0xFE;

/* Send data */
for(i=0;i<20;i++)
{ SSP1->DR = 0x41;
}

[b]SLAVE:[/b]

/* CLK, MISO & MOSI configuration */
SCU->GPIOOUT[3] &= 0xC0FF;
SCU->GPIOOUT[3] |= 0x0800;
SCU->GPIOIN[3] |= 0x40;
SCU->GPIOIN[3] |= 0x10;

/* SPI1 configuration */
SSP1->CR0 = 0x0007;
SSP1->CR1 = 0x0006; /* Slave Mode & SSP Enable */
SSP1->PR = 0xFE;

/* Receive data --> Status Register */
while((SSP1->SR & 0x04)==0);
for(i=0;i<20;i++)
{ buf[i] = SSP1->DR;
}

But I donÂ't receive anything. Which is the problem?

Thanks in advance.

Parents
  • 0 in reply to E. U.

    I haven't seen any comment saying what bit rate you are configuring your SPI for.

    Are you sure that the master is using a bit rate the same chip can support as a slave? Note that many SPI implementations have limitations on max bit rate for reception in comparison to the core frequency to make sure that the SPI receiver have time to sample the data at a proper interval before the master steps to the next bit.

    What bit rate do you want to send with, and what bit rate does the oscilloscope say you are using. The bit rate is easiest to check on the clock line, since it always show one pulse/bit.

    Have you measured the voltage swing on the MISO and MOSI signals? Have you connected them correctly so you haven't inadvertedly crossed the signal logic?
    MISO = Master In Slave Out.
    MOSI = Master Out Slave In.

    Remember that SPI is two-way, so you always send in both directions. If you write data to your slave, that data will be sent to the master when the master initializes a transfer in the other direction.

    And one very important thing: The slave-select. Do your master activate the slave-select input of the slave processor when you send data? If not, then the slave will ignore the SPI signals.

Reply
  • 0 in reply to E. U.

    I haven't seen any comment saying what bit rate you are configuring your SPI for.

    Are you sure that the master is using a bit rate the same chip can support as a slave? Note that many SPI implementations have limitations on max bit rate for reception in comparison to the core frequency to make sure that the SPI receiver have time to sample the data at a proper interval before the master steps to the next bit.

    What bit rate do you want to send with, and what bit rate does the oscilloscope say you are using. The bit rate is easiest to check on the clock line, since it always show one pulse/bit.

    Have you measured the voltage swing on the MISO and MOSI signals? Have you connected them correctly so you haven't inadvertedly crossed the signal logic?
    MISO = Master In Slave Out.
    MOSI = Master Out Slave In.

    Remember that SPI is two-way, so you always send in both directions. If you write data to your slave, that data will be sent to the master when the master initializes a transfer in the other direction.

    And one very important thing: The slave-select. Do your master activate the slave-select input of the slave processor when you send data? If not, then the slave will ignore the SPI signals.

Children
No data