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RTOS/ADS1118: Best practices for using Tiva C TM4C1294 QSSI with multiple ADS1118 boards

January 2, 2019, 10:06 am
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Part Number:ADS1118

Tool/software: TI-RTOS

I'm very new to programming TI processors so I hope my question isn't way off base.

I will be using a configuration that has a Tiva TM4C1294 processor. It will need to acquire data from 4 ADS1118s. Each ADS1118 will be used to acquire data from 2 tranducers. I will be using the QSSI interface on the Tiva processor to communicate with the ADS1118s. I plan on using SSI0Fss through SSI3Fss to chip select each of the ADS1118 boards. I plan on putting each of the ADS1118 boards into continuous sampling mode (set MODE bit to 0). I then plan on acquiring data from each board in a round robin fashion. I assume I can

1. select the ADS1118 I want to sample by setting it's NOT CS low,

2. wait for DOUT/NOT DRDY to be low to indicate a conversion is ready on the selected ADS1118

3. read the value from the ADS1118

It seems to me that if I don't care about the difference in power consumption, eliminating having to trigger starting a sample in single shot mode would be advantageous in sampling 8 TCs per Tiva.

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ADS124S06: Differential measurement

January 2, 2019, 10:06 am
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Part Number:ADS124S06

Hi all,

I have a doubt regarding differential measurement with ADS124S06.

Basically I want to measure a DC voltage between AIN1 (configured as positive input) and AIN3 (configured as negative input).The DC voltage to be measured comes from an isolated 4-20 mA transmitter. I want simply reading the voltage due to current across the sense resistor.

The voltage supply of ADC comse from a +12 V flyback converter followed by a low noise +5V_DC LDO. Thus +5V_DC is isolated. ADC reference voltage is directly the +5V_DC.

The high side of the below picture shown the theoretical connection while the low side of the picture show the main connections of the ADC124S06. Since the ground reference of ADC is different from the ground reference of the resistor would the ADC read the DC voltage across the resistor correctly? Should i connect the ground reference of the resistor with the ground reference of ADC? Or maybe may I wrongly connect the ADC for this task?

Thank you in advance for your help.

Best regards

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ADS8688EVM-PDK: SDCC Driver not Installing on Windows 10

January 2, 2019, 3:27 pm
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Part Number:ADS8688EVM-PDK

Hello team, 

Customer is trying to install the GUI file for the ADS8688EVM on 64-bit Windows10 machine. The GUI installation works fine, but the SDCC driver does not install properly and the whole installation fails. Is it possible the driver provided in the software files is not compatible with Windows10 (seems there is a dpinst.xml file missing)? I installed on my Windows7 64-bit machine with no issues. Please refer below for screenshots of the installation not working. 

Thanks!

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DAC80504EVM: DAC80504 becomes unresponsive after changing state of pin in EVM software

January 2, 2019, 3:48 pm
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Part Number:DAC80504EVM

First, glad to see that TI is shouldering support on it's customers and web-forum.

I was using the DAC80504EVM to find a set of register values I could use to initialize the device for my application. I did this and had gotten everything configured short of actually enabling the outputs, with the registers returning believable values, etc., when I decided on a whim to see what changing the state of the hardware pins in the software did. So, I changed RSTSEL to HIGH. All of the registers returned all 1s (0xFFFF) when I performed either a Read All or Read Selected, confirmed by my logic analyzer. Ooops. So, I set RSTSEL back to LOW. I have never been able to get a believable register read out of the device since. I have tried shutting everything down, disconnecting, and reconnecting and re-launching the software, without success. Is there anything I can do to restore functionality? I really need this device to work.

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DAC8775: DAC8775 Internal power supply design

January 2, 2019, 4:35 pm
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Part Number:DAC8775

Hi Sir

 I want to use DAC8775  but have a question. Reference evaluation board. I want Reduce PCB area, SO  I want to know that LP_X,LN_X,VPOS_IN_X,VNEG_IN_X:(A,B,C,D) .May I  connect the A,B,C,D to a node. 

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ADS8688EVM-PDK: File to restore flash on ADS8688EVM

January 2, 2019, 4:54 pm
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Part Number:ADS8688EVM-PDK

The solution mentions a file that has been recovered for the corrupted flash. Where do I find such file?

I have the same problem and have reformatted the flash but I cannot restore it without the file to write into it.

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ADC081S101: Communication with raspberry pi 3

January 2, 2019, 10:41 pm
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Part Number:ADC081S101

Hello,

I'm trying to translate what the engineer has just experienced. 

He tried to let ADC081S101 and raspberry pi 3 communicate with each other but failed. What should the communication protocol in this? Or How can have them communicate with each other

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ADS1291: the purpose of the negative supply rail

January 2, 2019, 11:57 pm
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Part Number:ADS1291

customer currently evaluating the ADS1291

trying to use LM27762 for the supply voltage, but seems to have too much consumption for the wearable device.

is there other voltage supply reference with lower operating consumption?

also, can we check that what is the purpose of the negative supply rail for the ADS1291?

is it for negative input signals?

Thanks

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ADC088S022: 1 read lag when switching channel

January 3, 2019, 3:44 am
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Part Number:ADC088S022

Hi,

I use the ADC088S022 converter and when i change the channel i want to read from i first get the previous channel value

and only then (on the next read) the value from the desired channel.

are you aware of such behavior? 

thanx

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Compiler/ADS1293: ADS1293

January 3, 2019, 4:49 am
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Part Number:ADS1293

Tool/software: TI C/C++ Compiler

Dear ti representative
I would to have the code for the EVM Ads1293 to use in a bluetooth device . currently the interface is with a USB type with the pc or lap top . we can easily modify it to sent our lab application.
Thank you

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DAC60501: LSB Parameter of a DAC

January 3, 2019, 6:04 am
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Part Number:DAC60501

I seek for clarification.

In one of the videos (Precision DACs: DC Specifications), LSB is calculated as equal to Vref/2^n. One reference (The Fundamentals of Mixed Signal Testing) I've come across, LSB is equal to FSRdut/2^n - 1; FSR is the measured full scale output range of the device.

These two equations don't appear to agree with each other. If anyone has the insights on how to resolve this, I would appreciate it so much.

Thank you.

 

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problem with reading data from ADS7825

January 3, 2019, 8:05 am
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hi,

I have interfaced ADS7825(in Parallel Mode) with AT90USB1286 microcontroller and I am able to get16-bit data from ADS7825.

But I came across a weird problem, let me explain about what I did: I used channel 0 and reaming channels are connected to ground.

Now I have given 2 V from Function generator( made by Agilent technologies) and I got 1.995V, good no problem for me here.

after this I removed the function generator, given 2V to channel 0 (of ADS7825) which is coming from an amplifier(LM324N based instrumentation amplifier followed by the differential amplifier), now I am getting varying voltage i.e 1.5V to 2.2V. i am not getting a constant voltage. now i removed the amplifier and I checked the amplifier output whether it is 2V or not, ohhh it is giving 2.018V(measured with fluke based DVM).

i don't know where is the problem. i think code wise no issue, even in amplifier is also working good  and all grounds are connected to the same ground.

could anyone give me the solution?

excuse me for bad English.

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Linux/ADS42LB69: Purpose of SYNC signal?

January 3, 2019, 10:01 am
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Part Number:ADS42LB69

Tool/software: Linux

Hello folks, i have a question about purpose of SYNC signal in ADC ADS42LB69?
In which case i should use this signal?

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Compiler/ADS1261EVM: New utilizing ADC and tools, need advice and guidance.

January 3, 2019, 11:44 am
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Part Number:ADS1261EVM

Tool/software: TI C/C++ Compiler

Hello,

I got the ADS1261EVM board and I successfully downloaded and installed the required drives and program to operate the board. I am trying to input and reconstruct using the Delta Signal application the following:

 sine wave at different frequency (i.e 1k, 10k, 1M, etc.) at a relatively small amplitude (i.e 10mV VPP and 5mV VPP).

I connected the signal generator the following way:

The positive input ---> to AIN7/AIN5

The negative input ---> to AIN6/AIN4

and I configure the following registers:

Data Rate to 400SPS

MUXP AIN7

MUXN AIN6

PGA  GAIN 64 V/V

Everything else remains as default, but I can't get a proper reconstruction, and I keep getting a fault error "PGA Low Alarm" 

Can someone please help me accomplish a proper set up?

 

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ADS8920B: Replacing a Microchip MCP3550 ADC with an ADS8920B

January 3, 2019, 2:14 pm
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Part Number:ADS8920B

Hi TI community,

I'm working on a design that uses the DAC8830 to generate sinusoids in the kilohertz range. The design currently uses an MCP3550 chip from Microchip (datasheet linked here) as a differential ADC, but its conversion time is far too slow to handle these frequencies.

I found the ADS892xB chip, and it seems suitable for this frequency range with good resolution. The MCP3550 had a 3-wire SPI interface, but I see that the ADS8920b has several serial digital outs as well as a serial digital in. Can this device still be operated with 3-wires? There is also a "CONVST" pin which I'm not sure what to do with for this application.

Also could the ADS8920b share a serial clock with the DAC8830? As long as we can control the DAC's sample rate, the ADC just has to be fast enough to sample the generated signal.

Thanks a lot for your time,

Ian

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Linux/ADS7843: work incorrect ,get event (get value x:0 y:4095 Rt:127 )

January 3, 2019, 6:51 pm
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Part Number:ADS7843

Tool/software: Linux

linux4.4 

driver:drivers/input/touchscreen/ads7846.c

dts:

ads7843: ads7843@00{
status = "okay";
compatible = "ti,ads7843";
reg = <0x00>;
interrupt-parent = <&gpio3>;
interrupts = <1 0>; //
spi-max-frequency = <1000000>;
pendown-gpio = <&gpio3 1 0>; //GPIO3_A1
//vcc-supply = <&reg_vcc3>;

ti,x-min = /bits/ 16 <0>;
ti,x-max = /bits/ 16 <8000>;
ti,y-min = /bits/ 16 <0>;
ti,y-max = /bits/ 16 <4800>;
ti,x-plate-ohms = /bits/ 16 <40>;
ti,pressure-max = /bits/ 16 <255>;

wakeup-source;

};

func:

ads7846_report_state

if (Rt) {
struct input_dev *input = ts->input;

if (ts->swap_xy)
swap(x, y);

if (!ts->pendown) {
input_report_key(input, BTN_TOUCH, 1);
ts->pendown = true;
dev_vdbg(&ts->spi->dev, "DOWN\n");
}

input_report_abs(input, ABS_X, x);
input_report_abs(input, ABS_Y, y);
input_report_abs(input, ABS_PRESSURE, ts->pressure_max - Rt);

input_sync(input);
dev_vdbg(&ts->spi->dev, "%4d/%4d/%4d\n", x, y, Rt);
printk("lintest ads7846_report_state %4d/%4d/%4d\n", x, y, Rt);
}

when touch the panel 

print:  lintest ads7846_report_state 0 4095 127

i don't know why...

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ADS1298: Question about 0.05Hz high-pass filter for ADS1298

January 3, 2019, 8:29 pm
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Part Number:ADS1298

Hi,

We are currently redesigning a resting ECG to use ADS1298. Since ADS1298 is a DC coupled frontend, we must implement a 0.05Hz -3dB highpass filter by software. Doing so by using an FIR filter will require too much memory and computational power for a small MCU like MKL16Z32VLH4 or similar. High-pass IIR filters are very tempting to use for their lower memory usage and computational power requirements. However, they have the non-linear phase response downside.

I have implemented the attached filter in C and it works exactly as expected. 

I have a few questions about this.

Is it fine to use this kind of filters (like the one shown in the attached images) for resting ECG?

What features of the ECG signal might be affected by these non-linearities on the phase?.

Can you recommend some alternative solution for a 0.05Hz high-pass filter?

I have read about compensating the IIR phase response by using an all-pass filter in cascade, but so far I have not found a way to design such a filter.

I will appreciate any comments, suggestions, links, that might help me with this problem.

Thank you very much in advance,

William

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LMP90098: Variations in RTD data

January 4, 2019, 12:16 am
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Part Number:LMP90098

Hey,

I am working on LMP90098 interfaced with MCU. A 3 wire PT-100 is connected with the AFE. There are huge variations in the data being read. I have tried out all the possibilities in changing the RTDs, VREFx1/2, capacitor between VIN0 & VIN1 etc., but the variation still remains. Voltages at RTD pins are constant. When I connect a standard resistor, the data(temperature) is constant. Tried this with multiple values of resistor and data is constant every time. But when I tried to read from RTD, there's variation. Kindly help me out here.

Thank you!

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ADS8881: Specs for Sub-sampling

January 4, 2019, 3:07 am
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Part Number:ADS8881

Hi, I am thinking of using a ~1MSPS ADC, like ADS8881,  to sub-sample a bandlimited signal around 10 MHz. The mentioned part specifies a -3dB bandwidth at 30 MHz, but apart from this there are no specs at all of the performance at frequencies above Nyquist. This holds for many other TI ADC I checked. How can I get information like SFDR when using your chips in this way?

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Compiler/ADS1293: ADS1293

January 4, 2019, 3:17 am
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Part Number:ADS1293

Tool/software: TI C/C++ Compiler

Dear  ti representative

Im am sorry for the typos in my previous posting and I would like to have the code for the ads1293 evm board .Our intention is to modify it a little for the a demo with a Bluetooth .please advise

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