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ADS8353: READ CFR and Data Convertion

rizal Suryana
Prodigy 90 points
Part Number: ADS8353

I used ADS8353 for double Langmuir Project, My controller, I am using Raspberry PI, I read REFDAC_A and REFDAC_B, it's work, the result is 1FF8H and 2FF8H respectively

but if I read CFR, the result always get 0000H. I confiured the ADS8353 as below

CFR = 0x8440

REFDAC_A = 0x9FF8

REFDAC_B = 0xAFF8

This command to read CFR, REFDAC_A and REFDAC_B

1. sent all zeros for Frame (F) with 32 CLK

2. sent CFR read command (F+1) 3000H with 48 CLK

3. sent all zeros for F+2 and get the data

and also I tried to read data convertion, to read data convertion, I sent the command as below

1. sen all zeros with 48 CLK

ADC_A input is 0.8V and ADC_B input is 1.67V

but I got the result of 0000H for ADC_A and FFFFH for ADC_B

is there mistake the command sent it ..?

 

  • 0
    TI__Guru 63126 points

    Hello Rizal,

    Thank you for your post and sorry for the delay in response.

    Can you confirm whether you are using dual-SDO or single-SDO mode? Have you tried sending 48 clocks per frame in all frames? Please refer to section 8.5.1 and Table 4. The minimum number of SCLK falling edges is required to validate a read or write operation.

    Best regards,

  • 0 in reply to Ryan Andrews
    Prodigy 90 points

    I use single-SDO mode, I have tried sending 48 clocks per frame in all frames,

    but the result is still no change, convertion results 0000H for ADC and FFFFH for  ADC_B

    to read the value of CFR register, the result is 0000H

    Best regards

    Rizal

  • 0 in reply to rizal Suryana
    TI__Guru 63126 points

    Hello Rizal,

    There are a couple things that you can try:

    1. First, the REF_DACx register powers up by default with the same register values that you are writing to them. Try eliminating those two register writes for now and only write to the CFR register (this is just to rule things out).
    2. Remember that at power-up, the device defaults to 32-clock, dual-SDO mode. After you write to the CFR register, the device should enter 32-clock, single-SDO mode. You should notice SDOB change to a high-impedance output. Try probing SDOA and SDOB before and after writing to the CFG register. Attempt to read data with some applied input voltage using the appropriate number of clocks (32 or 48). If SDOB is still toggling after changing the mode to single SDO, then something has not worked properly.

    Best regards, 

  • 0 in reply to Ryan Andrews
    Prodigy 90 points

    Hello Ryan

    I have tried but it still is not work.

    I think, the problem is the DAC can't write to register CFR, REFDACA and REFDACB

    could explain how to write to CFR, REFDACA and REFDACB for the first time ?

    I have tried to write to CFR, REFDACA and REFDACB like this:

    1. the REF_DACx register powers up, for this command I sent 00H in 48-CLK

    2. I wrote to CFR Register, for this command, I sent CFR bit function by 8440H (configured 32-CLK and single SDO) and 00H in 32-CLK

    3. I tried to read CFR Registers, for this command I sent the first all zeros in 48-CLK, the second is sent 3000H, zeros in 48-CLK and the last command is sent all zeros in 48-CLK and read the MISO.

    is it correct, what have I done ?

    Best regards

    Rizal 

  • 0 in reply to rizal Suryana
    Prodigy 90 points

    Hello Ryan

    I am sorry, I have wrong mentioned the device, it is not DAC but I mean the ADS8353. 

    Best regards

    Rizal

  • 0 in reply to rizal Suryana
    TI__Guru 63126 points

    Hi Rizal,

    Please do not write to the REFDACx registers at this time. It will make it easier to debug this issue.

    After power-up, the device uses the default mode of 32-CLK, dual-SDO. Write to the CFR register by sending 8440h 0000h. This will change the mode to single-SDO mode. Also, since you are setting bit 6 = 1, you are enabling the internal reference voltage. The internal reference will be connected to the REFIO pins. Can you probe the REFIO pins and confirm you get the correct default voltage?

    If the reference voltage is correct, send frames of 48 clocks with all 00h on DIN and probe SDOA and SDOB. Only SDOA should toggle with random data.

    Best regards,