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ADS1247: problem with signal clock

mil shar
Prodigy 140 points
Part Number: ADS1247
Other Parts Discussed in Thread: DAC8560

Hi.

I connect my ADS1247 with atxmega128a1u but when I check my clock signal through an oscilloscope, nothing will appear. I'm pretty sure nothing is wrong with my SPI config because I checked it by RFID module with a 4MHz clock signal and everything was ok. Also, other signals such as /CS and DOUT looks fine on the oscilloscope, but clock signal has just a pulse after the reset and then it goes low.

I really appreciate it if you can help me.

Regards.

  • 0
    TI__Guru* 97805 points
    Mil,


    I'm not sure I understand. Are you looking at the master clock signal (typically 4.096MHz)? Or are you talking about the SPI clock? Both would come from outside the device. If you are using the ADS1247's internal clock, this is activated when the CLK pin is tied to DGND, and is not observable.

    If you want to check that the device is running, use an oscilloscope to observe the DOUT/DRDY line. If the device is converting, you will see a small periodic pulse at coincident with the data rate.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph, thanks for your prompt reply.

    I'm talking about SPI clock signal. When I check the clock and /DRDY signals nothing will appear but DOUT/DRDY signal has pulses on the oscilloscope and it seems fine. My actual problem is that why I can't see the clock signal pulsing when I connect it to my micro? In another word, I should see the clock signal pulsing on the oscilloscope whereas I can see clock signal pulsing when I use another module like RFID on that port. I would say the clock pin on ADC was damaged but it has one pulse at the first.

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Mil,


    Because the SCLK originates from the ATmega128, I would start with that. The ADS1247 SCLK pin is only an input and shouldn't be able to shut off the SCLK or make it go away. The only possible problem that I can think of would be a bad solder joint that occasionally connects SCLK to ground.

    If you continue to have problems, can you please post a scope shot of the SCLK (whatever you're able to get out), DIN, DOUT and /CS? It might help to see these lines and how they might be corrupted.


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Guru* 97805 points
    Mil,


    There is one other thing to check. Make sure that your START pin is tied high. If the START pin is left floating, it may cause the device to unexpectedly turn on and off. This would cause some intermittent operation.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joesph,

    Here are my scope shots for my signals:

    DOUT/DRDY

    DOUT/DRDY

    DIN

    DIN

    /CS

    /CS

    SCLK

    SCLK

    I changed the scope time to 50ms just for the SCLK signal in order to show better. and about the START pin, as you said, it was always tied high and that didn't make any problem.

    Regards.

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Mil,


    It's a bit hard to see because of the limited resolution and the large time scale, but it does look like the device might responding. It might be best to change the time scale to show only 1 or 2 data outputs to be sure. Are you running the device at 50 SPS data rate? Also, can you provide a schematic?

    I'm not sure, but the fourth scope shot doesn't look like SCLK. It looks like what you would measure at /DRDY (pin 17). Can you please check your wiring just to make sure the connections are correct and you're measuring the SCLK at the proper pin?


    Joseph Wu
  • 0 in reply to Joseph Wu
    TI__Guru* 97805 points
    Mil,


    I wanted to see if you were able to get a solution to your problem. I think this error may be due to a limited resolution on your oscilloscope or due to a misplaced connection reading from the scope.

    If you have solved this problem then we can close out this post. If you haven't then please post back with comments so that we can continue debugging your circuit. Regardless, if I don't hear back from you I'll close out the thread soon. If you get locked out of this thread, just start a new thread and we can continue.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,

    I'm sorry for my delay in response, I was busy and thank you for your patient.

    Your statement is true, my resolution was not accurate, actually, everything was fine and after detecting my problem, I found that the reason I couldn't get an answer from my registers, it was the NOP instruction.

    I mean, after this code:

    SPI_transmit(0x40);
    SPI_transmit(0x03);
    SPI_transmit(0x01);
    SPI_transmit(0x00);
    SPI_transmit(0x03);
    SPI_transmit(0x42);

    I wanted to read my registers:

    SPI_transmit(0x20);
    SPI_transmit(0x03);

    but when I put "SPI_transmit(0xFF);" before "SPI_receive();" I got 0x000000 but when I removed "SPI_transmit(0xFF);" everything was fine. Now, I can read my registers accurately.

    Now, I have the same problem with my ADC reading. When I put "SPI_transmit(0xFF);" I got 0x000000 but when I removed it, I got 0x7FFFFF. Could you help me with that? I can't read from my ADC.

    Regards.

  • 0 in reply to mil shar
    TI__Guru* 97805 points

    Mil,


    I'm glad you were able to read the registers.

    When it comes to the data of 7FFFFFh, it's possible that you're receiving the correct data, but have something wrong or unexpected in the setup. Note that 7FFFFFh is the output for a positive full scale. It's possible that the ADC is measuring something that is full-scale or over-ranging the inputs.

    There are several things that can are likely to cause this read:

    1. The inputs are floating. This would likely pull apart the ADC inputs to get a very large reading

    2. The reference is shorted. If the reference is set to 0, then any input or even offset would be seen as an over-ranged input.

    3. The gain calibration register (FSR) is incorrectly set. If the FSR is incorrectly set, you might over-range the input faster than you may expect. If the offset register (OCR) is also incorrectly set, I'm sure you could do the same thing.

    4. The PGA is set to a larger gain than expected. If you have the gain set too high, a small input could give you an over-ranged value.

    I would verify all register settings to make sure you're making the correct measurements. In particular, check the input multiplexer settings and the PGA gain. Then I would measure the input voltage and reference values with a multimeter to make the voltages are what you expect. If you still have problems, repost back with register settings and the voltages so that we can review them.


    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi,

    Thanks for your pieces of advice, they helped me a lot!

    I want to verify the measurement by giving the input to ADC. Is it possible to do this without any analog input connected to ADC? If the answer is yes, how can I do this? I'm not familiar with the concept, so I really appreciate it if you help me. Now, I can read back the registers correctly but my input is float, so I get 7FFFFFh.

    Regards,

    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    There are a few simple measurements that you can do without having a voltage source on the input.

    First, if you have a few resistors, you can make a resistor divider from the supply that you can measure.

    Second, you can measure elements from the system monitor. In the MUX1 register for the ADS1247, there are several options in the system monitor set by the MUXCAL bits. A setting of 011 sets the inputs to a temperature sensor which is about 118mV at 25C and has a drift of 405uV/C. A setting of 110 measures the analog supply, and will measure (AVDD-AVSS)/4. Finally a setting of 111 measures the digital supply and will measure (DVDD-DGND)/4. If I remember correctly, both supply monitors have some error, and the accuracy may be somewhere near 5%.

    I've used the temperature sensor to test the devices many times. You can also vary the input by placing a finger on the device to warm it up a few degrees. When running these tests make sure that the internal reference is enabled.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points
    Hi,
    Thanks for your reply. That's really helped me.

    Now, I connect DAC8560 through a jumper to AIN0 pin of ADS1247 and generates 0-2.5V with the resolution of 100mV.

    ADC Configuration:
    SPI_transmit(0x40);
    SPI_transmit(0x03);
    SPI_transmit(0x00);
    SPI_transmit(0x01); //Bias voltage is applied to AIN0
    SPI_transmit(0x30); //internal reference is always on, Normal operation
    SPI_transmit(0x40); //gain = 16, SPS = 5

    I've got some measurements, but I can't verify them. Could you help me with these numbers?
    71 F0 EBh, 66 82 BDh, 71 28 A1h, 5F 13 21h, 76 A9 95h, 6A C2 96h, 6A 62 13h, 69 25 EFh, 5C 13 68h, 5F 57 E0h, ...
    But when I want to measure single-point voltage, the output value will be 7F FFFFh.

    Regards,
    Milad
  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    Just looking over your SPI communications, I don't think it's measuring what you want it to.

    The bytes you send are:
    40 WREG starting at register 00
    03 Write 4 bytes
    00 BCS off, Set input mux to AIN0 and AIN0
    01 Set VBIAS to AIN0
    30 Internal reference always on, internal reference always selected
    40 PGA=16, Data rate=5SPS

    The main problem is that both AINP and AINN are connected to AIN0 (as commanded by the first byte) and and both are then also connected to VBIAS which is now connected to AIN0 (as set up in the second byte). With both inputs connected to each other, you should be getting some sort of offset measurement. If you want to make a measurement of AIN0 and AIN1, you would put in 01 instead of 00 for the third byte.

    Instead it looks like you're getting some large numbers. Did you change the calibration coefficients in OFC or the FSC? Did you run a calibration command? To start, I would leave those settings alone and not run a calibration.

    Also, how are you reading the data? Do you run the device in continuous conversion mode, and then just clock in SCLKs or do you do an RDATA command? If the you use the latter, I would first run an SDATAC command and then issue the RDATA when you want to read the device. By issuing the SDATAC, you can prevent a read of the data from being interrupted by the completion of a new conversion.

    Were you able to do the other reads (and get correct data) from the ADC that I had suggested in my previous post?


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi,

    Thanks for your thorough response!

    For your last question, I should say that I couldn't get any correct reads, I just got 7F FFFFh.

    For your second question, I'm not setting any calibration settings right now.

    Your first question: the reason I set the third byte to 0x00 (I knew that wasn't right) was that when I set it to 0x01 I got 7F FFFFh. Actually, I thought because I had just AIN0, so there is no need to set AIN1.

    And for your third questions, I use RDATA mode for reading and of course, before RDATA command, I issue SDATAC command just like the pseudocode suggests in the datasheet. Plus, I don't use any interrupt in my code, but the main problem in my code is that waiting for DRDY pin to transition low doesn't operate correctly, because when I check it on the scope, DRDY would go to a low transition about every 15sec but conversions operate repeatedly. In other words, I expect the following line operates every 15sec, but it doesn't.

    while (gpio_pin_is_high(DRDY_pin));//DRDY pin is active low

    my code has been attached to prevent any confusion.

    Fullscreen ADS1247.c Download 
    int main(void)
{
	//Enable the device by setting the START pin high;	
	gpio_set_pin_high(RESETpin);
		
	// Set CS to the device low, to select the device
	gpio_set_pin_low(CSpin);
	_delay_ms(10);
		
	// Setting START Pin High, Enables the Device (like WAKEUP Command), to begin a conversion
	gpio_set_pin_high(STARTpin);
	_delay_ms(10);		
		
	// Send the RESET command (06h) to make sure the device is properly reset after power up;
	SPI_transmit(0x06);
	_delay_ms(6);
		
	// Send SDATAC command (16h) to prevent the new data from interrupting data or register transactions;
	SPI_transmit(0x16);
	_delay_ms(10);
	
	//Write the respective register configuration with the WREG command (40h, 03h, 01h, 00h, 03h and 42h);
	SPI_transmit(0x40);
	SPI_transmit(0x03);
	SPI_transmit(0x01);
	SPI_transmit(0x01);			//Bias voltage is applied to AIN0
	SPI_transmit(0x30);			//internal reference is always on, internal reference selected, Normal operation (default)
	SPI_transmit(0x40);			//gain=16, SPS=5
	_delay_ms(1);
		
	//Send the SYNC command (04h) to start the ADC conversion;
	SPI_transmit(0x04);
	_delay_us(2);
		
	// Clear CS to high (resets the serial interface);
	gpio_set_pin_high(CSpin);		

	int Voltage = 0;
	int interval = 2621;//generating 100mV from 0-2.5 in DAC8560
	while(1)
	{
		DAC_Voltage_Generator(Voltage);
		
		//Wait for DRDY to transition low;
		while (gpio_pin_is_high(DRDYpin));
	
		//Take CS low;
		gpio_set_pin_low(CSpin);
		_delay_us(5);
	
		//Send the RDATA command (12h);
		SPI_transmit(0x12);
		//_delay_ms(1); // added by me
			
		//Send 24 SCLKs to read out conversion data on DOUT/DRDY;
		ADC_Output = SPI_receive();
		ADC_Output = SPI_receive();
		ADC_Output = SPI_receive();
		
		_delay_ms(2);
	
		//Clear CS to high;
		gpio_set_pin_high(ADC_Ext_CS);
		
		_delay_ms(10);
		Voltage = Voltage + interval;
	}
}

    Regards,

    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    If you weren't able to make any correct measurements, I would check the reference voltage. Make sure that it comes up to 2.048V and that it is stable. I would measure it back with a multimeter. Also make sure that the proper reference input is selected. If your reference somehow ends up as 0V, or is some really small voltage, any input may make the ADC give a full scale reading.

    Just in case, I would also read back the OFC and FSC just in case something went wrong.

    Also, you mentioned that you had the ADC inputs set to AIN0. I want to make sure you understand that the ADS1247 ADC is fully differential. This means that you select a positive input (AINP) and a negative input (AINN). The ADC output data is a measurement of AINP-AINN. Note that if AINN is higher than AINP, then the measurement is negative and the ADC output code is represented in two's complement notation. When making measurements, make sure you select a negative and positive input for the ADC.

    If you're making a series of single-ended measurements, you would select maybe AIN3 as AINN, and make measurements of AINP with AIN0, AIN1, and AIN2. Note that with your bipolar supplies, you can tie AIN3 to ground. This will keep the input measurement within the input range of the PGA. I have your schematic from one of your previous posts but it doesn't show your measurement connections. Out of curiosity, what are AIN0 to AIN3 connected to?

    I won't have a chance to look over your code until tomorrow, so I'll get back to you on that later.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points
    Hi Joseph,

    I checked the Vrefout and Vrefcom which both of them are 2.5V and they were stable. And about the proper reference input, if I understand your saying, I set the REFSELT[1:0] bits to 10 as it says internal reference selected.
    Furthermore, I checked OFC and FSC registers which are 000000h and 800D40h, respectively when PGA = 16.

    As I mentioned before, I connected DOUT pin of DAC8560 to AIN0 pin of ADS1247 and the rest of AINs (AIN1, AIN2, AIN3) are not connected to anything. As I infer from your statement, I can't measure the DAC values when I have just one AIN, right?

    Regards,
    Milad
  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    First, the FSC register should be a value near 400000h, not 800000h. A large value of 800000h may double the output value that you get out of the ADC.

    For the measurement, you need to have a connection to one of the other analog input pins. The ADS1247 is a fully differential ADC, so the measurement will be the difference between the positive analog input and the negative analog input. By floating the negative input, the input voltage isn't going to be set and you won't get any usable measurements.

    I believe that you're using bipolar supplies. Attach AIN1 to ground, connect AIN0 to the DAC, select the AIN1 as the AINN and AIN0 as the AINP and make a few measurements.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,

    I will put into action your suggestions, meanwhile, could you verify my code so I just focus on my design? Because I'm not experienced with electrical issues, so I need to be sure of my code, then I'll get help from a person who knows these matters.

    Regards,

    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    I had looked at your code earlier. I should work as is, but the only thing that I would change is the order of initializing the device. I would set START high first, then bring /CS low to communicate with the device (and then sending the RESET as the first command).

    Beyond that, I don't see any other issues - it's a rather short segment of code. I will say however, that I don't do a lot of coding, so I'm probably not the best to review it.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points
    Hi Joseph,
    I think I found my problem. I checked my reference voltage (Vrefout and Vrefcom pins) with multimeter and oscilloscope, and got voltage around 0V with oscillation which as you said earlier it must be 2.048V and stable. I use 22uF capacitance between Vrefout and Vrefcom. What can be wrong with my design?

    Regards,
    Milad
  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    It is possible that the reference is unstable. The VREFCOM must be connected to an AC ground through a resistance of less than 10Ω. This connection is required for the stability of the reference. If the impedance is higher than 10Ω, you may connect a capacitor of at least 0.1uF between VREFCOM and an AC ground node.

    On your schematic, you show connections to several resistors (S3J4, S3J1, S3J2). I would make S3J2 a 0Ω resistor so that VREFCOM is set to ground and then remove the other resistors.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,

    Thanks a million for all your help! That was the reason I couldn't get measurements.

    Now I can get measurements through DAC with the resolution of 1mV, But OFC registers are not set and I just use the SELFOCAL command with 3500ms delay. I get 20 roughly nonsense outputs like 0x7Fxxxxh and then turn to 0mV, 1mV, ..., 127mV and 128mV which is the full-scale range (PGA = 16). My question is how can I remove the first outputs?

    Regards,

    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    I'm glad that you were able to get the reference to work. I hadn't noticed the VREFCOM connection until I reviewed all the previous posts.

    However, I'm not sure I understand what you're seeing. Are you getting bad data for the first 20 outputs after waiting to settle, and then running a calibration? I think I need a more detailed explanation of the effect that you're seeing, with more timing information.

    If it just takes extra time to get good data. It may be the reference settling. You do have a 22uF capacitor, which may take extra time to start up. However, this should only require an extra 2ms or so. If you have extra filtering on the input that's not shown on the schematic, then you may also have some similar settling time.

    It would help for you to post the bad (and the good data that you get). I'd want the raw data coming out of the ADC, not converted to any other units that you're measuring.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,
    I attached my output file from ADC which shows the raw data.
    The only command I added to the code was the SELFOCAL command with the Daley of 3500ms. Plus, the OFC registers are 0.
    Sorry for the confusion!

    Fullscreen raw data.txt Download 
    F0 75 9E
F0 7C 6A
F0 83 D5
F0 84 F2
F1 0C F3
F2 0D 53
F3 0B 0D
F4 12 80
F5 0F CF
F6 0E 2C
F7 09 C8
F8 09 DE
F9 03 8F
FA 06 66
FB 00 43
FB F6 87
FC F3 E1
FD EE 8E
FE F6 03
FF EE EA
00 ED 0C
01 E1 E1
02 E7 3E
03 E3 78
04 E2 69
05 DF 38
06 D8 FD
07 D8 5B
08 D5 FD
09 D4 FC
0A CD AA
0B C7 2B
0C C7 55
0D C8 8F
0E C9 8A
0F C1 1E
10 C1 08
11 AE 5B
12 B9 97
13 A4 FD
14 B3 84
15 B1 00
16 AF 9C
17 AA 90
18 A3 9F
19 A2 03
1A A3 2F
1B 9A F6
1C 98 A6
1D 93 B4
1E 93 73
1F 8E 05
20 8A 90
21 87 97
22 86 87
23 72 DF
24 7A 20
25 78 8D
26 78 F9
27 6B 76
28 6C E9
29 6B 6E
2A 68 EB
2B 63 F8
2C 5B FB
2D 56 06
2E 55 9F
2F 51 75
30 57 F0
31 4F D0
32 4B FA
33 49 D9
34 50 C4
35 48 B2
36 47 94
37 3E 98
38 33 E8
39 39 F8
3A 2B 3A
3B 35 3E
3C 31 BF
3D 2B 40
3E 2C CF
3F 24 E2
40 21 38
41 1D 3C
41 FD C0
43 19 B5
44 18 0B
44 F0 09
46 10 C7
46 EE C3
48 0D C4
48 E6 DA
4A 04 10
4A FB D0
4B FA FC
4C FB 70
4D D5 8F
4E D1 21
4F EE 71
50 DB 8B
51 C7 47
52 C3 06
53 E0 D6
54 B6 59
55 DB A8
56 AF 79
57 B8 96
58 B3 CC
59 D3 75
5A A5 E0
5B CA BB
5C C8 56
5D 99 AB
5E 95 DA
5F 8C 0A
60 91 54
61 B3 0F
62 85 45
63 86 C9
64 82 1C
65 82 90
66 A0 36
67 76 3D
68 76 2D
69 71 61
6A 70 79
6D 19 7F
71 19 60
74 81 34
74 B3 10
76 BC 75
77 6E 30
76 EE 45
77 8B 59
7B 46 31

    Regards,
    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points

    Milad,

    I don't know what that is. I've converted your file to show the measurement:

    This doesn't look like some exponential time constant capacitive charging from an RC filter. It may be some sort current charging a capacitor similar to an integrator, but I don't know how you have your circuit set up. Also, this measurement spans most of the positive full scale. If you let this run further, does it eventually rail out?

    What are you measuring and what value are you expecting to get? Do you have a schematic? What is the amount of time over which this data is taken?

    Joseph Wu

  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,

    Actually, there was a problem with my code which I found it. After that, to ensure myself, I set the ADC to ambient temperature and got the 119mV out of it. Now, I measure it with the DAC through PGA=16, SPS=5 and set the offset registers which I should get the 0-128mV, but after some nonsense measurements like 5, then it goes 0, 1, ..., 126mV. I mean some data has been missed. Is it ok or should I do something about it?

    Regards,

    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points
    Milad,


    In my previous post, I misunderstood what you had explained.

    I'm still not sure what error you are seeing, but it does look like there is some delay from the start of the readings to when the DAC starts to move the input voltage up. I'm not sure if this is will be a problem for you. At this point, it does look like a real delay, and not just some nonsense data.

    If you have newer data that shows more of an error, or some nonsense values that are read. You can post it back to this thread and we can discuss it.


    Joseph Wu
  • 0 in reply to Joseph Wu
    Prodigy 140 points

    Hi Joseph,

    This attachment file shows the raw data with PGA=2 and SPS=160 through a DAC(0-1024mV).

    I've got so many measurements like this which after a few seconds, everything looks fine, so I think it works well, doesn't it?

    Fullscreen 3426.raw data.txt Download 
    00 40 C9
FF F0 92
FF EF 2D
FF EF 8D
FF F2 36
00 00 D2
00 1F DB
00 40 50
00 60 2C
00 80 6A
00 9F 2D
00 C0 48
00 DF 19
00 FF FC
01 1E D2
01 3D B6
01 5C C2
01 7E AF
01 9E B5
01 BE 45
01 DD 0A
01 FD 82
02 1B 87
02 3E 14
02 5C 51
02 7B 6C
02 9B 4D
02 BA FC
02 DB AB
02 FA 66
03 19 71
03 3A 25
03 59 6A
03 7A CC
03 98 9B
03 BA 76
03 D9 F7
03 F8 80
04 19 25
04 38 62
04 57 94
04 78 F4
04 96 A2
04 B8 55
04 D7 F7
04 F7 2A
05 15 BE
05 34 25
05 55 99
05 74 1C
05 95 32
05 B4 78
05 D3 DF
05 F4 B3
06 14 06
06 34 42
06 52 03
06 71 2F
06 92 C1
06 B2 62
06 D2 61
06 F2 D7
07 12 1C
07 33 C0
07 52 4F
07 71 B4
07 91 F1
07 B1 45
07 CE 61
07 EE 7A
08 0E 0B
08 2F DB
08 4F 22
08 6E 4B
08 8D 54
08 AE 40
08 CE 09
08 ED 4A
09 0B E4
09 2E 0D
09 4E 23
09 6D 8C
09 8C 21
09 AC C6
09 CC A0
09 EB 62
0A 0A DE
0A 2B 64
0A 4B AC
0A 6A 36
0A 8A 5D
0A AA 99
0A CA 89
0A EA 5C
0B 09 8D
0B 29 18
0B 48 52
0B 68 11
0B 89 68
0B A9 21
0B C6 C3
0B E7 B0
0C 06 FF
0C 26 B3
0C 47 B0
0C 66 8C
0C 85 EE
0C A5 B8
0C C4 68
0C E5 33
0D 05 92
0D 24 B0
0D 44 99
0D 64 D3
0D 83 67
0D A4 1F
0D C3 0C
0D E3 19
0E 03 69
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2C FC 1F
2D 1D 1B
2D 3B 8D
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2D 9A 9C
2D B9 80
2D D9 93
2D F9 7E
2E 17 ED
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2E B7 A6
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2E F6 FD
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2F F4 2A
30 12 09
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32 8E BA
32 AE 35
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33 CB E5
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34 0A C1
34 2A 5F
34 48 D2
34 69 1D
34 88 FD
34 A7 A2
34 C9 36
34 E8 92
35 08 C3
35 27 B0
35 46 BD
35 66 F7
35 87 A3
35 A5 A1
35 C7 D9
35 E5 AE
36 06 76
36 25 4D
36 46 16
36 65 15
36 86 38
36 A5 83
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37 04 D5
37 24 33
37 43 94
37 63 91
37 83 6F
37 A2 0B
37 C3 A7
37 E2 C4
38 01 89
38 23 34
38 41 34
38 60 82
38 80 34
38 A0 A1
38 C0 42
38 DF B7
39 00 CB
39 1F FC
39 40 03
39 5E 2D
39 7F 2F
39 9F 3F
39 BF 6C
39 DD F2
39 FD 26
3A 1D B1
3A 3E 07
3A 5C 41
3A 7D 5D
3A 9D A6
3A BA B8
3A DB 0B
3A FB FF
3B 1C 5A
3B 3A B6
3B 5A 2D
3B 7B 35
3B 9A A8
3B BA DC
3B DB 15
3B FA 2F
3C 18 76
3C 39 54
3C 59 0C
3C 78 97
3C 97 76
3C B7 AD
3C D6 CA
3C F7 EC
3D 17 21
3D 36 33
3D 56 40
3D 75 EC
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3D B5 D4
3D D7 D1
3D F6 A7
3E 16 0C
3E 34 FB
3E 53 2C
3E 73 6D
3E 93 37
3E B3 85
3E D3 2D
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3F 12 B7
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3F 51 FA
3F 71 51
3F 90 1F
3F B0 D7
3F D0 3F
3F F0 6E
40 10 7F
40 30 21
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40 8E E1
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41 AC C3
41 CC 82
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43 0B 74
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44 09 2E
44 28 72
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4A 5A 72
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4A D7 1B
4A F8 6F
4B 18 B8
4B 38 45
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4B B6 53
4B D5 3C
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4C 73 56
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4D 51 CC
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4D B1 6F
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4D F2 99
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4E EE 49
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4F 4E 9F
4F 6E F1
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5B F0 46
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6E 06 1C
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6E E5 82
6F 05 55
6F 24 6F
6F 43 D3
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6F 82 7B
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6F C2 F9
6F E1 83
70 03 40
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71 9F 5A
71 C0 2B
71 DE 00
71 FE 4C
72 1D C2
72 3C B7
72 5D 96
72 7C F9
72 9C 04
72 BC C1
72 DB 94
72 FB B3
73 1A D3
73 3A 92
73 5A 6B
73 7B 93
73 9A 29
73 B9 9D
73 D9 B1
73 F9 D6
74 19 5D
74 37 A3
74 58 5B
74 77 FF
74 96 DD
74 B6 8A
74 D6 7F
74 F7 13
75 15 56
75 36 1B
75 55 A6
75 74 5F
75 95 21
75 B5 80
75 D4 62
75 F4 E1
76 14 FE
76 33 BB
76 54 79
76 72 94
76 93 C0
76 B2 EA
76 D3 56
76 F2 EB
77 13 B8
77 30 F4
77 50 C0
77 71 76
77 91 50
77 AF D6
77 CF A9
77 EF 9F
78 0E 3C
78 30 24
78 4F 22
78 6E C7
78 8F 0E
78 AF 1D
78 CF 41
78 EE 30
79 0E 14
79 2C 53
79 4D C1
79 6C 91
79 8D F5
79 AC D7
79 CB 95
79 EC 4A
7A 0B 66
7A 2A 32
7A 4A 78
7A 6A C3
7A 8A 15
7A AA 11
7A CB 1E
7A E9 99
7B 09 26
7B 28 C3
7B 47 CC
7B 69 02
7B 88 33
7B A7 E7
7B C9 40
7B E6 3C
7C 06 0E
7C 26 8D
7C 45 94
7C 64 FB
7C 84 7C
7C A4 40
7C C5 22
7C E5 30
7D 03 D2
7D 23 61
7D 44 03
7D 63 4E
7D 84 16
7D A3 BA
7D C2 81
7D E1 A8
7E 01 D4
7E 22 A4
7E 42 3D
7E 61 73
7E 80 74
7E A1 1A
7E C0 7C
7E E0 25
7E FF 4A
7F 1E E7
7F 3F 29
7F 5F 6C
7F 7E A1
7F 9F 19
7F BF 09
7F DD A4
7F FE 22
7F FF FF

    Regards,

    Milad

  • 0 in reply to mil shar
    TI__Guru* 97805 points

    Milad,

    I think it looks ok. If you're just ramping up the signal with the DAC, then it appears that you're going from near 0 to a full scale:

    If you're still concerned with the measurements, you should set a constant input voltage, and then measure it back with a precision multimeter. If you take several measurements spaced from 0 to full scale, you can see the gain and non-linearity error from the ADC. You'll want to use something like an Agilent 3458A where the non-linearity error is likely 0.1ppm for multimeter range (as your standard). A handheld multimeter is probably not good enough for precision measurements.

    At this point, it looks like you're making correct measurements. I'll close this post for now. As always you can post back with more questions if you have any.

    Joseph Wu