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ADS7951-Q1: Read data (TMS570)

Michal Timm
Intellectual 810 points

Part Number: ADS7951-Q1
Other Parts Discussed in Thread: HALCOGEN

Hi,

I would like to use ADS7951-Q1 with TMS570 MCU.

SPI configuration using HalCoGen: SPI1, 16bit, Clock phase checked, clock polarity unchecked, extra delays before and after CS assertions

REFP = 2.5V
+VA = 3.3V
+VBD = 3.3V

I tested sequence as simple as possible:
1. Device Power Up,
2. Device Operation in Manual Mode as default
3. Read 4 times channel 1. (write 0x1880)

My results below:
Frame 1

Frame 2

Frame 3

Frame 4

Unfortunately, I cant see channel 1 (0001) on bits 15-12. I tried with different channels and I did not achieve proper results. 
What can be wrong?

  • 0
    Intellectual 810 points

    I found source of this issue.

    As usual, I added serial resistors (50 Ohm) to CLK, CS, MISO, SIMO lines. From my expirience it helps to smooth signals, especially in test environment with contact plate and cables. This time, waveforms looked nice on the osciloscope but chip was not respond correctly.

    I was fix it by decreasing resistor on CLK line (to 10 Ohm) and now everything is ok. I tried several configurations (CLK 1MHz-10MHz) and serial resistance for CS, MISO and SIMO could be even more than 100 Ohm but for CLK line max was 20 Ohm.

  • 0 in reply to Michal Timm
    TI__Guru**** 201436 points

    Hi Michal,

    Why does it takes so long for MISO signal (4th signal from top) get back to default state: