ADS131A04EVM: starting conversion

Axel Schmidt19

Part Number: ADS131A04EVM
Other Parts Discussed in Thread: ADS131A04,

Hi,

I have a problem with setting up the ADS131A04. I use the ADS131A04EVM, but connected the SPI lines to a Raspberry Pi. Reading and Writing the registers works fine. I'll use the asynchron slave mode, and also the interrupts are generated (by the ADS131) and received (by the Pi) without problems. Following data sheet figure 109, I set some registers I need, enable ADCs, send wakeup and lock the registers. Every command is acknowledged as expected. But - there is no conversion value in the frames I read. I connected only J7 of the EVM (n-input about 1.3 V, p-input about 2.0 V), the remaining inputs of the EVM are open. I would expect quite accurate values for the used input and some small noisy values on the others, but I read simply "0" for all bytes. The registers 02h..05h don't report any error. What happens here, what do I miss? Is it possible to destroy the analog inputs in a way the digital output is constant "0".

over 9 years ago

0 Brian Pisani over 9 years ago

TI__Mastermind 38745 points

Hello Axel,

Can you send me the exact sequence you do all of these things and also the register settings?

Brian

0 Axel Schmidt19 over 9 years ago in reply to Brian Pisani

Prodigy 40 points

Hallo Brian,

I used a python script for reading/writing:

#!/usr/bin/python
import spidev
import time
import RPi.GPIO as GPIO

spi = spidev.SpiDev()
spi.open(0,0)
spi.mode = 0b01
spi.max_speed_hz = 16000000

GPIO.setmode(GPIO.BCM)
GPIO.setup(24, GPIO.IN, pull_up_down = GPIO.PUD_UP)

i = 0
n = 0

def Interrupt(channel):
  global n
# -- read data and registers 02h..05h  
  resp1 = spi.xfer2([0x22, 0x03, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
  resp2 = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
  resp3 = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
  resp4 = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
  n  = n + 1
  if n == 100:
    print ''.join(["0x%02X " % x for x in resp1]).strip()
    print ''.join(["0x%02X " % x for x in resp2]).strip()
    print ''.join(["0x%02X " % x for x in resp3]).strip()
    print ''.join(["0x%02X " % x for x in resp4]).strip()
    print ""
    n = 1


try:
# avoid wrong bit sync
  resp = spi.xfer2([0x06, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
  time.sleep(0.1)
  resp = spi.xfer2([0x05, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
# --------------------------------------------------------
#    GPIO.add_event_detect(24, GPIO.FALLING, callback = Interrupt)  
# -- interrupt generation starts without wake-up !!!???
# -- >>> TI-Blog: "expected behaviour"; wait for READY Word 0xFF 0x04 and start with UNLOCK
  while i == 0:
    i = i + 1
#   -- unlock
    resp = spi.xfer2([0x06, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- read all registers
    resp = spi.xfer2([0x20, 0x14, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- lock    
    resp = spi.xfer2([0x05, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- wait for lock response   
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    print ""
    time.sleep(5)
#  end while
  while i == 1:
    i = i + 1
#   -- unlock
    resp = spi.xfer2([0x06, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- CLK2 (0x0E): 8 - fICLK/8, 0 - fMOD/4096
    resp = spi.xfer2([0x4E, 0x80, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- ADC_ENA (0x0F): F - enable all ADCs 
    resp = spi.xfer2([0x4F, 0x0F, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- wakeup
    resp = spi.xfer2([0x33, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- lock
    resp = spi.xfer2([0x05, 0x55, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
#   -- wait for lock response
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    resp = spi.xfer2([0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00])
    print ''.join(["0x%02X " % x for x in resp]).strip()
    print ""
    GPIO.add_event_detect(24, GPIO.FALLING, callback = Interrupt)  
    time.sleep(2)
#  end while
  while i == 2:
    i = i + 1
#  end while
  while True:
    time.sleep(1)  
#  end while
except KeyboardInterrupt:
  spi.close()
  GPIO.cleanup()
  print "\nTschaui"
  print ""
# end try

The output is the following, which is (beside the zeros for the conversion values) what I expect to see:

0xFF 0x04 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x06 0x55 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x60 0x14 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x04 0x03 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x01 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x60 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x3C 0x08 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x86 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x00 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x05 0x55 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF

0x22 0x00 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x06 0x55 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x2E 0x80 0x00 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF 0xFF
0x2F 0x0F 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x33 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x05 0x55 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x22 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00

0x22 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x62 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00

0x22 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x62 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00

0x22 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x62 0x03 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00
0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00


Tschaui

When I'm correct, I'll have about 62 interrupts per second. To avoid a mass of data on the screen, I write only every 100th set. The time seems ok, i.e. I see a new block roughly every 1.xx second.

By the way: The only thing I can't explain is the value of 0x22 at first position of every block except the first one. the first one starts correctly with 0xFF 0x04.

Do you have a suggestion to make this work?

Best regards

Axel

0 Brian Pisani over 9 years ago in reply to Axel Schmidt19

TI__Mastermind 38745 points

Hey Axel,

I don't mean to be picky, but could you just summarize what you do in the sequence in a list form and perhaps just summarize the register settings in a list? That way I can easily tell which part your sequence is missing.

The 0x22 at the beginning of each output frame is the "ACK" for a "NULL" command. It simply means that the device is reporting the contents of register 0x02 in the very next byte.

Regards,
Brian

0 Axel Schmidt19 over 9 years ago in reply to Brian Pisani

Prodigy 40 points

Hallo Brian,

no problem, it's not much. In a first step I read all registers to have a complete picture, i.e. UNLOCK, READ (0x20, 0x14), LOCK. Then, I do

- 0x06, 0x55: UNLOCK

- 0x4E, 0x80: CLK2 register, fICLK / 8, fMOD / 4096 (resulting in 62 interrupts per second)

- 0x4F, 0x0F: ADC_ENA for all ADCs

- 0x33: WAKEUP

- 0x05, 0x55: LOCK

- 0x00: wait for LOCK response

After that sequence I enable the interrput routine in Python. The MODE PIN STATUS register is correctly 0x01, all write commands are acknowledged correctly. Interrupts are generated, but channel data are "0".

That's it. Do you have any suggestions?

Best regards

Axel

0 Brian Pisani over 9 years ago in reply to Axel Schmidt19

TI__Mastermind 38745 points

Axel,

I think I have identified the mistake. When you attempt to send the WAKEUP command, you send 0x3300. In fact the WAKEUP command should be 0x0033. The reason you do not receive an F_OPC fault is because 0x3300 is a valid command: RREG register 0x13 - the result of which is 0x00. In the end, you never actually send the WAKEUP command so all the conversion results appear as 0x00. I believe if you change that one line in the script it should work.

Brian

0 Axel Schmidt19 over 9 years ago in reply to Brian Pisani

Prodigy 40 points

Hallo Brian,

you're completely right, it was my fault. Tricky that the response is in this particular case exactly what one could expect also for the (wrong) WAKEUP command. Thanks a lot!!!

Best regards

Axel

0 Daniel Carelli over 9 years ago in reply to Axel Schmidt19

Prodigy 10 points

Hi Axel,

I'm looking to set something up very similar to what you have. I'm just curious, are you able to get the full 128ksps with simultaneous sampling with your setup?

-Daniel

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ADS131A04EVM: starting conversion