Tiva C, SSI with AS5048 in "Framed Mode"

Hi,

You must configure your SSI peripheral for Motorola/Freescale protocol with word length 16 bits, as you must send only one word at a time. What really version of this protocol is better to discover by yourself by reading the user manual - is clear explained and is not difficult to understand. This is better than giving you the right answer now, since you will use this module in other projects - and this way you get experience with the micro and peripheral.

If any other problem(s) in implementing the software, many helpers are here to assist.

Petrei

Chris Henschel said:

be great if I can get some help here due to a very short time to market, product lunch will be around Christmas. 

While that's unfortunate - none here caused/contributed to your short-fuse application.  Shouldn't your protest land at the feet of those requesting - not blameless/innocents here?

Best help results when requesters have proved that they've made (some) effort to understand and attack their unique application.  No such evidence surfaces w/in your post.

MCU manual is beyond 1k pages - SSI/SPI chapter is thick - well detailed.  And - there are multiple SW examples sprinkled w/in the API SW and this forum.

Your "question" is likely answered quickly/convincingly by your read/review of the MCU manual.  Suspect that's just what you did in your past PIC design - is it not?  MCU Manual greatly details (via timing diagrams) the various means of SPI data flows, signal timings & signal edges.  Your job then reduces to simply choosing the best "mated" MCU mode for your slave IC application.  Again - it appears that you've not made this effort - and it very much is required.

Hello,

Thanks for your answers. I am sorry for my late reply. I have had some hardware problems that were causing also problems with the SPI. My first post was not written well; of course I had made investments before bothering you and you are absolutely right that the time to market is not the problem for this forum. Anyway, meanwhile I studied the SPI chapter in the datasheet :).

To fill the SPI RX FIFO a dummy writes to the SPI modules is mandatory. That’s actually one thing what I wanted to know, if this is possible by hardware.

The SPI is working fine, either in TI-RTOS or Driver mode (the ones from the ssi.h header). I used the Freescale Frame Format with polarity 0 and phase 1. Currently I am transmitting only one 16 bit value at once; this is to slow for my application. I would like now to fasten the reading, and then I could increase my filter to increase the angular position accuracy.

I think I have not understood the uDMA right: Will the uDMA give me any speed advantages than using the interrupt when the RX-FIFO is half full (SSI_RXFF) and copy four 16-Bit values at once (the FIFO is 8 values deep)? Are there any SPI uDMA examples in TI-RTOS?

I am also confused what functions I should use. I found out that mixing the TI-RTOS ones with the native driver functions is not a good idea e.g. linker error when using SSIIntRegister. Currently I am using the TI-RTOS only because of the nice Task environment and the Webserver Example :).

I am looking forward to your replys

Chris

Hello Again

I cant find any example or documentation about the SPI configuration for uDMA in TI-RTOS. So I put the SSI Module from the peripheral library.

When I send a 0xFFFF to the SPI my Sensor is answering with the current measurement. Now I thought I request data by sending the 0xFFFF as long as the RX FIFO is full and then copy the 8 Values from the FIFO at once but the RXFIFO seams not getting filled up and the Flag is never set.

I setup the SSI Module as followed:

	// The SSI0 peripheral must be enabled for use.
	SysCtlPeripheralEnable (SYSCTL_PERIPH_SSI2);
	SysCtlPeripheralEnable (SYSCTL_PERIPH_GPIOD);

	// Disable SSI function before configuring module
	SSIDisable (SSI2_BASE);

	//Set IO clock as SSI clock source
	SSIClockSourceSet(SSI2_BASE, SSI_CLOCK_SYSTEM); //    SSIClockSourceSet(SSI0_BASE, SSI_CLOCK_PIOSC);

	// Configure the pin muxing for SSI2 functions
	GPIOPinConfigure (GPIO_PD0_SSI2XDAT1);
	GPIOPinConfigure (GPIO_PD1_SSI2XDAT0);
	GPIOPinConfigure (GPIO_PD2_SSI2FSS);
	GPIOPinConfigure (GPIO_PD3_SSI2CLK);

	// Configure the GPIO settings for the SSI pins.
	GPIOPinTypeSSI(GPIO_PORTD_BASE,
			(GPIO_PIN_0 | GPIO_PIN_1 | GPIO_PIN_2 | GPIO_PIN_3));

	// Configure and enable the SSI port for SPI master mode.
	SSIConfigSetExpClk(SSI2_BASE, 80000000, SSI_FRF_MOTO_MODE_1,
			SSI_MODE_MASTER, 10000000, 16);

	//Enable the SSI0 module.
	SSIEnable(SSI2_BASE);

My idle function looks as followed:

	if (HWREG(0x4000A00C) & (1 << 4)) { //checking the SSI_SR-RFF Bit from SSI2 (recieve FIFO full)
		int rawSum = 0;
		uint32_t data;
		uint8_t ii;
		for (ii = 0; ii < 8; ++ii) {
			SSIDataGetNonBlocking(SSI2_BASE, &data);
			rawSum += data & 16383;
		}
		int16_t pos = divRoundClosest(rawSum, 8);
		ReadAngle(pos, time);
	}

	SSIDataPutNonBlocking(SSI2_BASE, 0xFFFF);

Can you help me?

Cheers,

Chris