How to get input level of MISO

Robert R

Other Parts Discussed in Thread: CC1200, AM3359

Hello,

I got an AM3359 on a beaglebone black (Master) and try to talk to a CC1200 (Slave) via SPI. To start a conversation I set the chip select manual to active (low) and if the CC1200 is ready for conversation it also set the MISO to low (this process I can see on my oscilloscope). To check this I have to read the input level of MISO Pin but I cannot find a way to do this.

I already tried to mux the pin to a GPIO and get the value of DATAIN register but that stop the connection to CC1200.

I look for something like: while( HWREG("Register on am3359") & MISO_INPUT_BIT ); to wait till MISO goes low.

thanks for replies

Robert

Edit: I try to use the SPIDAT_0 Bit in MCSPI_SYST register but this works only if I set the SYSTEM_TEST Bit in MCSPI_MODULCTRL. While doing this the Transmission stops.

Is it possible to check the MISO state with MCSPI_SYST Value or have I done something wrong?

over 11 years ago

0 John Murphy1 over 11 years ago

Expert 1210 points

Did you find a solution?

In our design, we simply electrically linked the MISO pin to another spare GPIO on the AM335x so that we could read it directly without changing MUX settings or anything special.

0 Vineeth Balan over 11 years ago in reply to John Murphy1

TI__Intellectual 1640 points

Hi Robert .

" I try to use the SPIDAT_0 Bit in MCSPI_SYST register but this works only if I set the SYSTEM_TEST Bit in MCSPI_MODULCTRL. While doing this the Transmission stops."

Which pin have you configured as MISO ? If SPIDAT_0 is configured as MISO (as input) then SPIDAT_0 bit should reflect the line state.

0 Robert R over 11 years ago in reply to Vineeth Balan

Prodigy 230 points

Hello Vineeth,

I tried it this way:

HWREG(SOC_SPI_1_REGS + 0x0124) |= 0x0100; // set MISO to Input
HWREG(SOC_SPI_1_REGS + 0x0128) |= 0x08; // activate system test mode

If i do this there is no clk. I can see that mcspi write in TX0 but no transmission. If I just set MISO to Input without system test mode, the mcspi works normally but there is activity in SPIDAT_0 Bit of MCSPI_SYST register.

My actual configuration:

/* Clock and pinmuxing */

    McSPI1ModuleClkConfig();
   McSPI1PinMuxSetup(); // for general -> GpioPinMuxSetup in gpio.h, GPIO declarations in pin_mux.h
   McSPI1CSPinMuxSetup();

   /* McSPI configuration */

   McSPIReset(SOC_SPI_1_REGS);
   McSPICSPolarityConfig(SOC_SPI_1_REGS, MCSPI_CS_POL_LOW, 0);
   McSPICSEnable(SOC_SPI_1_REGS);
   McSPIMasterModeEnable(SOC_SPI_1_REGS);
   McSPIMasterModeConfig(SOC_SPI_1_REGS,MCSPI_SINGLE_CH, MCSPI_TX_RX_MODE,   MCSPI_DATA_LINE_COMM_MODE_1, 0);
   McSPIClkConfig(SOC_SPI_1_REGS, 48000000, 1500000, 0, MCSPI_CLK_MODE_0);
   McSPIWordLengthSet(SOC_SPI_1_REGS, MCSPI_WORD_LENGTH(8), 0);
   HWREG(SOC_SPI_1_REGS + 0x012C) |= 0x03000000; // TCS in MCSPI_CH0CONF

How I have to configure the McSPI1 register to see something in MCSPI_SYST without going in system test mode?

@John: this is my last resort, but I thought there is a software solution provided to do this.

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How to get input level of MISO