Getting garbage from the National Semiconducter ADC088S052 8 channel ADC

BillDer

I am at a loss to explain why I get the same twelve bits on all 8 channels when I should be getting 0's or close to 0 on 7 of them and be getting something close to represent 1.5 Volts on chan. 0. I first tried to use the SPI code from Beau in the OBEX then found this driver fromCanniba lRobotics who posted the ADC088S052 Driver.
I did adjust the Clk, Din, Dout, CS pins accordingly.
Anyone with experience with this chip or with SPI code that overlaps the address out with the MSB of the data in? The timing chart for the ADC088S052 is attached.

JonnyMac

I don't have that chip but I have written code that overlaps sending and receiving bytes via SPI. Based on the docs for that chip, I'd give this a whirl:

pub adc_read(setup) : adc

  setup := (setup & %111) << (32-5)                             ' shift to bit31

  outa[ADC_CS] :=  0                                            ' select
  
  repeat 16
    outa[ADC_DIN] := (setup <~ 1) | 1                           ' output setup bit   
    outa[ADC_CLK] := 0                                          ' clock a bit    
    outa[ADC_CLK] := 1
    adc := (adc << 1) | ina[ADC_DOUT]                           ' get bit from dout

  outa[ADC_CS] := 1                                             ' de-select
  
  adc := (adc >> 4) & $FF                                       ' cleanup

You'll need to setup the IOs (see constants in code) prior to calling this the first time.

Kirk Fraser

BillDer, Do tell us if the above post solved your problem. If not, I can get my old code for input from a similar TI chip with 11 channels which worked on a BS2. Converting it to a Propeller program though I can't help with.

BillDer

Thanks for the code. I will try this out tonight after work.

BillDer

Thanks to everyone, I was able to talk to the chip last night. This forum is the best I can't believe how helpful everyone is.
Thank you.
Bill