SPI Driver using GPIO'S

Stefan Fischer

Hi,

I allready used all SPI Ports on my Controller now i need one more, so i was thinking of writing a Driver using GPIO'S for this.

Has anybody done this before or is there a code example for C2000 Devices ?

cheers!

S.Fischer

over 13 years ago

0 ALESSANDRO GUERRESCHI over 13 years ago

Intellectual 580 points

Hi!

I have to use two SPI devices too! Have you got an example on how to do it using GPIOs?

I would like to find a way to point a GPIO to the SPISTEA bit of the SPI protocol. Becouse it is like a ChipSelect, but I can't do it! Thanks!

0 Chris McDermott over 13 years ago

Intellectual 700 points

Much easier to use multiple GPIO chip select lines and work each with the software than to do an SPI bus by bit-banging.

This is done by assigning the SPI clock and data lines to their pins, but leave the SPI CS line as a GPIO output. Then when you want to access a device on the SPI bus, activate that devices' CS line, let the SPI peripheral do it's thing, then de-activate the devices CS line. This works for most SPI devices which allow and/or require the chip select to be constantly active during accesses. Only those few devices which use the CS as a frame select and expect the CS line to de-activate between bytes/frames etc cause a problem. Using multiple GPIO lines as chip selects also require some code to make sure you don't try and access two devices on the same SPI bus at the same time, but this is usually easy to do by using a single task to work the SPI bus, doing one operation at a time, and have other requesting tasks send an inter-task message, push an entry onto a FIFO, or other inter-task communication method with the operations to be done on the SPI bus.

0 ALESSANDRO GUERRESCHI over 13 years ago in reply to Chris McDermott

Intellectual 580 points

Hi!

I have tried to put low the GPIO61:

Configuration:

 // GPIO61 is Output
 EALLOW;
 GpioCtrlRegs.GPBMUX2.bit.GPIO61 = 0; // GPIO61
 GpioCtrlRegs.GPBPUD.bit.GPIO61 = 0; // Pull up
 GpioCtrlRegs.GPBDIR.bit.GPIO61 = 1; // Output
 EDIS;

Use:

GpioDataRegs.GPBDAT.bit.GPIO61 = 0; //chipselect low: receiving data

SpiaRegs.SPITXBUF = 0x00; /* Send dummy data */
 while (SpiaRegs.SPISTS.bit.BUFFULL_FLAG == 1){} /* Wait for SPITXBUF is free */
 while (SpiaRegs.SPISTS.bit.INT_FLAG == 0){} /* Wait for RX to finish */
 x = SpiaRegs.SPIRXBUF; /* Read RXBUF */
 data_channelA1 = x;

GpioDataRegs.GPBDAT.bit.GPIO61 = 1; //trasmission finished

when I start the receive data istruction, but it goes up immedeately. How can I take low the GPIO voltage for the time of the communication?

Have I to use timer? Please help me! Thanks!

0 Chris McDermott over 13 years ago in reply to ALESSANDRO GUERRESCHI

Intellectual 700 points

I've found it is more reliable to use GPBCLR and GPBSET registers to write to GPIO output pins, and use GPBDAT just for reading what value is being output onto the pin.