Reading a LTC1865 ADC

[JTCullins]

Thank you for your response.
Actually I am using the LTC1865 . It is full duplex which means it accepts commands and sends data at the same time. I can get stuff out' I would not call it data but bits coming out reading CH1 but never CH0. I am sure it is something simple that I am not seeing. I have used the LTC1298 and it works great and is very rugged chip, however it is only 12 bit and I need 16 bits.

[Dave]

JT, You MUST send the channel information as soon as you drop the CONV line low. acording to the spec. Are you doing this? Like you said, this is a full duplex device and as such it will require you to send the channel information along with the first 2 clock pulses as well as receive the first 2 bits of the result which are the bits 15 and 14.

[JTCullins]

Thanks Dave, I was busy yesterday build boards for an on going project. I will give it a shot today.
I would like to have used the shiftout and Shiftin as I did on the 1298 but I guess I need to bit bang it myself.
I hope it will be fast enough.
Thank you for your help
JT

[Dave]

JT, Personally I would use a SPI interface if your chip of choice has one...

[JTCullins]

I would like to but how do I do a full duplex with the SPI interface? I have never used it. I use Pic Basic Pro
Any help would be great.
Thanks

[JTCullins]

Dave, I just looked at the data sheet on the PIC16F818 chip that I use and I don't see anything where you can transmit and recieve at the same time on the SPI bus.
The only way I can see, and granted I am not what you would call a good programmer, is to send the first two config bits and read the first two bits in ( 15 and 14 )
then use shiftin to read the last 14 bits in. Not sure if that would work or not but I plan to try it tomorrow.
Thanks
Jt

[Dave]

JT, That is the purpose of SPI. You would load the SSPSR register with the first 8 data bits to send and, as they were being sent the same register is being loaded with the firts 8 bits of data from the A/D. You just have to do it 1 byte at a time but it should be Much Much faster than bitbanging it. Read about it in the spec sheet for the 16F818. It's under SSP port....

[JTCullins]

I can't use the SPI in the chip. This is for a board that is already designed and built and the pins are wrong for it.
Thanks
JT