ADC0831 pulsout vs high/low

Franny

Howdy, in the code below there's the line "PULSOUT CLK, 210" and I was just wondering why couldn't this just be a high followed by a low?

' -----[ Subroutines ]----------------------------------------------------- 
ADC_Data:   
LOW CLK   
LOW CS   
PULSOUT CLK, 210    
SHIFTIN DataOutput,CLK,MSBPOST,[adcBits\8]   
HIGH CS RETURN

tomcrawford

PULSOUT has a defined length (210 times whatever the BS-2? units are). HIGH/LOW makes a pulse of whatever length it happens to be.

Franny

would it not work with high/low or is it a lot faster with pulsout?

tomcrawford

Don't know whether that would work with that particular ADC or not. Try it and see. But why not just use the PULSOUT?

As to whether HIGH/LOW is faster/slower than 420 usec (210 times 2 Usec), don't know that either off the top of my head. Set up your measuring device and try it.

Franny

Yeah sure, I use PULSOUT all the time,I just want to know why. Thanks : ]

Chris Savage

Speed is another consideration. PULSOUT is one command whereas separate HIGH/LOW commands may take more time to execute since each instruction has to be fetched from EEPROM. I'd have to write some code and look at the results on my logic analyzer, but if speed were an issue I would definitely base it on that.

Franny

Thank you! : ]

Chris Savage

As a side-note the LOW Clk statement in the subroutine is also a waste of time. I know it's our code, but it should be executed once in the initialization section of the program and that's it. There's no need to make that pin low each time the subroutine is called.

Franny

Useful to know that! How would you write the PBasic code below into the SimpleIDE C format?

CS              PIN     0 
CLK             PIN     1 
DataOutput      PIN     2

Genetix

Franny,

The ADC0831 requires one pulse on the clock line after being activated to do the
voltage conversion.

Maybe this subroutine from StampWorks Experiment # 28 makes more sense.

Read_0831:
  LOW CS                                      ' enable ADC
  SHIFTIN DataIn, Clock, MSBPOST, [result\9]  ' read ADC
  HIGH CS                                     ' disable ADC
  RETURN

result is a BYTE variable, which is 8 bits, so I am guessing that the extra bit, that isn't needed anyway, just gets dropped.

In PBASIC, I/O pins can be defined as a PIN variable or a constant (CON).
This Propeller C lesson defines constants for I/O and also shows how to use SHIFTIN in C.
http://learn.parallax.com/propeller-c-simple-protocols/bit-masks-better-code

I am not sure if Jon's (JonnyMac who wrote StampWorks) 9-bit SHIFTIN trick will work correctly in C.
I didn't get any build errors when I tried it.

Franny

Cool, so it's const int. Thanks

Franny

Genetix wrote: »

Franny,

The ADC0831 requires one pulse on the clock line after being activated to do the
voltage conversion.

Maybe this subroutine from StampWorks Experiment # 28 makes more sense.

Read_0831:
  LOW CS                                      ' enable ADC
  SHIFTIN DataIn, Clock, MSBPOST, [result\9]  ' read ADC
  HIGH CS                                     ' disable ADC
  RETURN

result is a BYTE variable, which is 8 bits, so I am guessing that the extra bit, that isn't needed anyway, just gets dropped.

In PBASIC, I/O pins can be defined as a PIN variable or a constant (CON).
This Propeller C lesson defines constants for I/O and also shows how to use SHIFTIN in C.
http://learn.parallax.com/propeller-c-simple-protocols/bit-masks-better-code

I am not sure if Jon's (JonnyMac who wrote StampWorks) 9-bit SHIFTIN trick will work correctly in C.
I didn't get any build errors when I tried it.

Extremely useful, Thanks! : ]