Shiftin with external Clock howto ?

[RFsolution]

Hi

I have a hardware situation where I need to read a 12bit serial output
clocked by his own clock

If i'm right all Shiftin commands generates an own clock signal
is there a way to use an external clock with some sort of shiftin

When the chipselect pin goes low, the clock is present and starts sending the 12bits
once finished Chipselect goes high etc...

Any help welcome

[HenrikOlsson]

As far as I know there is no PBP command to do it. You could, depending on the speed of your external device clock, roll your own or perhaps you could use a PIC with a SSP module capable of operating in slave mode.

Since, if I understad correctly, YOU initiate the read by pulling the CS\ low (ie you know exactly when the data is starting to come in) it should be quite possible to roll your own routine if the speed is fairly low. It's nothing I've done personally though but off the top of my head something like:

InputData Var WORD
InputPin VAR PortB.0
ClockInput VAR PortB.1
CSOutput VAR PortB.2
i var BYTE
 
InputData = 0          ' Initialize
CSOutput = 0          ' Pull CS line low to initiate transfer
 
For i = 1 to 12         ' Get 12 bits
While ClockInput = 0    ' Wait for clock going high
Wend
 
InputData = InputData << 1 + InputPin
 
While ClockInput = 1    ' Wait for clock going low
Wend
 
Next                        ' Do next bit until we have 12
 
CSOutput = 1

/Henrik.

[mackrackit]

What device are you working with?

[RFsolution]

Well the device is a 16F877 which talks to a DAC7611, i have no access to the 16F877 software and would like to use the data (value) send to the DAC in another circuit
So i want to read what the 16F877 is sending to the dac by a small MCU