GPIO on F2803x Devices as Input and Output

Hi,

Moving your post to right forum to be better answered.

Thanks & regards,
Sivaraj K

Hi Jawwad,

Just wanted to confirm, are you trying to emulate I2C using GPIOs ie software implementation of I2C?
Also, check processors.wiki.ti.com/.../I2C_Tips

Regards,
Gautam

Thanks Gautam,
Yes I want to emulate I2C using GPIO pins. I worked the same day, when i posted the Q, a couple of hours bec the project timelines are short.

Here is my implementation that works for me

I simply define SCL as output.
SDA as input with pullup disabled and external pull up. Avoid read modify write instructions and change SDA to input/output as required.


#define __SDA_ASINPUT EALLOW;GpioCtrlRegs.GPADIR.bit.GPIO19 = 0;EDIS;
#define __SDA_ASOUTPUT EALLOW;GpioCtrlRegs.GPADIR.bit.GPIO19 = 1;EDIS;

u_char SWI2CRead(u_char ACK){
u_char i, Data=0,x;
__SET_SDA_IO
__SDA_ASINPUT
usec(1);
__CLR_SCL_IO
usec(1);
for (i = 0; i < 8; i++) {
__SET_SCL_IO
usec(1);
x = __RD_SDA
if(x)Data |=1;
if(i<7)Data<<=1;
__CLR_SCL_IO
usec(1);
}
if(ACK==I2C_ACK) __CLR_SDA_IO //SDA = 0 to send ACK, 1 for NACK
else __SET_SDA_IO //Master sends ACK for more data and NACK other wise
__SDA_ASOUTPUT
usec(1);
__SET_SCL_IO
usec(1);
__CLR_SCL_IO
return Data;
}

Just wanted to ask if this is the correct approach. Will this produce any bus conflicts ? etc.

Being a software implementation of I2C I don't see any conflicts happening. Secondly I've never seen anybody working on the same though I was very much fond of implementing software_uart, spi and i2c with other manufacturer's mcus.
If the above is really able to replicate the I2C peripheral then the work is really appreciable :)

Goodluck & Regards,
Gautam

Hi Gautum

Thanks for the reply. The code works perfectly. I am already communication with EEPROM and RTC on software I2C. The hardware I2C is being used by Gyro, Accelero etc.

I have posted it here and any one could use and modify it. There is one caution though, the pipeline architecture of DSC may cause timing issues at different clocks and I would recommend use of Logic Analyzer or a dual channel oscilloscope to check for right timings and put nops to ensure things happen in order.

This is specially true for SPI where at high speed a GPIO Chip select may de-select the device while the transmission is still in progress.

Good Luck

Jawwad

Excellent and thanks for the tips!

Regards,
Gautam

Thanks Gautum. Once I have tested it fully, I will post the code here.
And u are doing a marvelous job on this forum, really amazing. Keep up the good work