SPI test in bidirectional mode

[gdt]

Hy everyone,

I try to test the bus api with SPI. I just connect SPI1 Output to SPI1 Input to get the data I send (loopback). I just achieve to send the data (I see the data on the bus) but I cannot get what I send…

I see that there is some problems with bidirectional communication on SPI
(wavecom.com/modules/movie/sc … php?t=1187)

Hi kapilsinghi,

Although I am not an expert in interfacing the hardware, but I can tell you that in Wavecom Wireless CPU the MISO and MOSI signals are mutiplexed.
You can either write or read from the SPI bus but not at the same time.

Hence, the devices, which act as shift register and read and write at same time cannot be used with this configuration (I suppose so). However, for device like flash memories (which are interfaced with SPI) or camera devices, you can send the data and then read it back (as the read/write is not done simultaneously).

Feedback from other forum members is also solicited here.

Best Regards,
Open AT Fan.

I it any solution for this problem ?

adl_busSPISettings_t busSettings;
ascii data[8+1] = "\0";

	busSettings.ChipSelect =	ADL_BUS_SPI_ADDR_CS_NONE;
	busSettings.ChipSelectPolarity = ADL_BUS_SPI_CS_POL_HIGH;
	busSettings.Clk_Mode = ADL_BUS_SPI_CLK_MODE_3;
	busSettings.Clk_Speed = 25;
	busSettings.DataLinesConf = ADL_BUS_SPI_DATA_BIDIR;
	// busSettings->SPI.GpioChipSelect DC
	busSettings.LsbFirst = ADL_BUS_SPI_MSB_FIRST;
	busSettings.WriteHandling = ADL_BUS_SPI_WORD_HANDLING;

	spiHandle = adl_busSubscribe (ADL_BUS_SPI1 , (adl_busSettings_u *) &busSettings );

//returns 0

busAccess.Address = 0;
	busAccess.AddressLength = 0;
	busAccess.Opcode = 0; 
	busAccess.OpcodeLength =  0;
	busAccess.Size = ADL_BUS_SIZE_BYTE;

	sReturn = adl_busWrite(spiHandle, &busAccess, dataLen, data);
// returns 0


	sReturn = adl_busRead(spiHandle, &busAccess, size, data);
//return 0

Thanks in advance,

Best regards,

gdt

[jan]

Hi gdt,

I’m pretty sure that what you are trying to do cannot work…

The read command generates the clock and decodes what is received on the bus. But at that time, the send command is already finished, so there will be no more pulses to receive on the data line…

Best Reagrds,
Jan

[gdt]

Apparently it’s possible on small microcontollers.

I want to use SPI to exchange data with a MCP2510 (CAN 2 SPI IC).
I think it should work if I use opcode and address but I don’t know if this IC will work properly if the clock is interrupted for 5 periods between address, opcode and data.

Thanks for your quick response

Best regards,

gdt