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DDC264EVM input

Other Parts Discussed in Thread: DDC264EVM, DDC264

I'm confused about where I'm supplying the input signals to the DDC264EVM. The board has 4 DDC264 chips which means it should take 256 (64x4) inputs. My best guess looking at the board is that i'm only given 10 inputs, which i'd wire into by connecting to the middle pin of jumpers 1-10.

If this is the correct interpretation, I'd like some confirmation since its a rather drastic reduction in inputs, and I'm curious about the purpose behind the 256 resistors  that are connected to the 256 inputs.

If i'm mistaken, I'm like to know where i should be connecting my inputs

  • Hi David,

    Jumpers J1 through J10 are on the Analog Input Board. The purpose of this AIB is to take a DC voltage input on connector J12 and divide this into a very small current on each of the individual 256 resistor channels. The J1 - J10 jumpers are only used for selecting the biasing of banks of resistors. With these jumpers you can select if you want some channels to be biased at VIN from J12 or VREF which can be provided from the DDC264 board if J16 on the DDC264 board is installed. The AIB is simply part of the evaluation module and meant to provide the same input to all 256 channels for your evaluation. If you would like to provide your own input signals you can desolder any of the 256 resistors you like and add signals there. A detailed schematic of the AIB can be found on page 39 of the following EVM user's guide: http://www.ti.com/lit/ug/sbau186/sbau186.pdf 

    Page 6 of the same document also has some useful information about the AIB resistor channel mapping.

    To map each resistor to each input channel and the channel name in the GUI. Please use pages 36 and 37, along with page 39 and the attached excel document.

    Be aware that the channel numbers listed in the excel document are only valid when the GUI is configured to display all 256 channels.

    Please let me know if I can help you further.

    Regards,

    -Adam Sidelsky

    8308.DDC264_EVM_CHANNEL_MAP.xlsx

  • Thanks for your response. I certainly wasn't thinking that the board only had 1 input. Would desoldering the resistors and applying my own inputs cause any issues with the software interpretting the signals?

    also i'm having a problem installing the software. Windows doesn't automatically detect the drivers. and when i manually try to point  to the Driver folder i get the message that windows was unable to install my device because the driver software could not be found. I'm running windows 7.

  • David,

    Desoldering the resistors and adding your own is fine as long as you make sure to keep your signals within the input range that the DS specifies for the particular input range you have selected. Exceeding the input range will simply saturate the inputs. The reason we use the high value resistors is so that we can divide our input voltage into very small currents which simulate the very small currents coming from the Xray photodiodes for example. For example, in range 3 on the DDC264 the input range is typically 150 pC. 

    On the software:

    Do you have a windows XP machine available? The solution does work on windows 7 but it is slightly more difficult. I can provide you with instructions for this if you cannot find a windows XP machine to use. The issues you are seeing with the drivers are typical on windows 7 if the specialized instructions are not followed so don't worry.

  • no, i only have a windows 7 machine, can you please direct me to these instructions

  • David,

    Please follow the instructions given by Jason Bridgmon in the following thread. Let me know if you are unclear on any of the steps and I can help you.

    http://e2e.ti.com/support/applications/high_reliability/f/30/p/160538/944844.aspx#944844

    Thanks,

    -Adam

  • thanks for all your help, 

    I think I've now installed the drivers and have things working, but I'm not sure. The software opens, but i can't figure out how to take measurements. There isn't a record/stop button, and while there are several timing options, they seem to be mostly about changing duty cycles. nDVALID read almost looks like the variable i want, because it lets me change how frequently the chip samples, but i don't see any option that lets me set how many times to sample or specify how long i would like to sample for.

    when i try the 'fast data' button with default settings it records for a very small fraction of a second. This isn't enough time to see if there's actually any information in the signal.

  • David,

    Glad to hear that the software is working. 

    The way this EVM works is that you set the appropriate clock speeds, convert time, and channel count, then click "write" to write this to the FPGA. Next you will set the DDC registers how you would like and click "write CFG". Next click "Refresh All" to make sure all the settings you request are being saved correctly. After this completes you can press "Fast Data" to capture the data. Each time you press "fast data" the FPGA will instruct the DDC to sample "nDvalid read" number of times using the clock speeds, channel count, and convert time you set. For example, if you are reading all 256 channels and you set nDvalid read at 2048, each of the 256 channels will be sampled 1024 times on the A-side and 1024 times on the B-side. This EVM is not setup to read data back in real time continuously. To make sure you are receiving data back from the device, navigate to the "graph" tab on the GUI, click the "Noise Bar PI" rectangular button, not the radio button. You should see a Noise Bar plot similar to page 24, figure 20 on the DDC264EVM user's guide. Your noise values may differ based on your environment but as long as you see data and not zero's, you are fine. The output you see on this plot and on the "all channels candlestick" section are simply the averages of all readings taken on all channels (See page 21, figure 17 for an example). For example, using the numbers from above, if you set nDvalid read to be 2048, each blue dot is the average of 1024 samples on the A side and each red dot is the average of 1024 samples on the B side.

    Hopefully this answers some of your questions,

    Regards,

    -Adam Sidelsky

  • I followed your steps (write->write cfg->refresh->fast data) and then navigated to the noise bar pl plot, but there is no data

  • David,

    Here's a quick check to make sure the board is being recognized by your system:

    1. Connect the board to your PC with the USB cable.

    2. Power up the board using 5V on both the J12 and J5 connectors making sure to connect your negative connection to the pin labeled xDGND on J12 and AGND on J5, the other two connections on J5 and J12 should be +5V.

    3. You should hear the PC recognize the board with the normal "device found" noise. 

    4. Next launch the GUI

    5. If the board's drivers are correctly installed you should see the following text as black :

    6. If the board is not installed or powered correctly you will see the following text as red:

    7. Please note that this check is only performed when launching the GUI. If the board loses power after the GUI was already started, you will still see black text as in step 5.

    If you only see red text, you probably have a driver issue. Please let me know. Are you making sure to press F8 and disable driver enforcement each time you restart your PC?

  • The letters are black, and powering up the board in this way does create data.

    Does this mean there's a problem powering the board through the USB? I would prefer doing it that way.

    Also when I was calculating the timing variables i'll ultimately want, the specs didn't seem to work out: I want to measure on the order of 50uA, the max range is listed as -0.6 to 150pC (by the way, where do i actually make this range selection) which would mean i'd need to integrate at < 3uS and the lower bound seems to be 320uS. This is too big even if I wanted to measure on the order of a 1uA and the datasheet says it can measure microamps so i must be missing something.

    lastly, i'm still a bit confused about collecting a larger sequence of data. When you said "This EVM is not setup to read data back in real time continuously", does this mean i can't visualize it realtime (which is fine) or that there is actually no way to run an experiments that lasts on the order of seconds to a couple minutes?

    Thank you again, you've been incredibly helpful so far. and i feel like i'm taking advantage since all your answers just lead to more questions

  • David, 

    I am glad to help!

    You can only power the DVDD of the chip using USB if you place a jumper on positions 2/3 on J19. I have not used this before. I would be careful since the USB power may introduce additional noise depending on the quality of signal it is outputting. The other thing to watch out for is the maximum output current of the USB port. Depending on your settings, I have seen up to 300mA of current on the DVDD supply and I'm unsure of your USB drive capability. The other option you have is to use a DC barrel jack to power the whole board. For details on this please see the last page of the DDC264 schematic included with the EVM guide. You will need a 7V-10V DC adapter, center positive and set jumpers J20 and J22, also make sure to set J19 to position 1/2. 

    The range selection is made using the "DDC Configuration Registers". Using Bit 10 the MSB and Bit 9 the LSB you can select in binary range 3 (1 1) range 2 (1 0) range 1 (0 1) or range 0 (0 0). Please see Table 1 in the DDC EVM user's guide. Do you have this guide?

    Our device's max range is 150 pico-coulombs, fractions of 1 uA. Where in the DS does it mention uA range capability?

    I don't remember which version of the chip the EVM is built with but the DDC264C is 3ksps max sample rate and the DDC264CK is 6Ksps max sample rate. This is the highest sample rate we offer.

    You cannot visualize data in real time. The EVM is configured to sample the inputs based on the timing and quantity you specify in the register settings. Once you press fast data, the chip samples as you have requested and returns the data to you. To run an experiment that lasts "a few minutes" you would need to write your own software to sample the inputs continuously and analyze the data accordingly. 

  • on the first page of the DDC264 datasheet under 'description' it states:

    "Adjustable integration times range from 160μs to 1s, allowing currents from fAs to μAs to be continuously measured with outstanding precision."

    do you know of a more appropriate chip for measuring microamps?

  • Hi,

    uA's is border line for the DDC products. Quickly you saturate them. This is a long shot, but you may want to look into the AFE4400 or the AFE4490

    Regards,

    Eduardo

  • Hi to all and sorry to interfere but are days that i'am not able to obtain values different from zero from ddc264evm.

    I have a ddc264evm and I power on with usb. I have winxp and the software go right : i have installed j16 to carry vref on AIB but I go on to obtain zero value : I thought to obtain different value because  I haven't link nothing to AIB. What I wrong or it's right to obtain zeros on all channels?I power the ddc264evm with USB ,I put the j19 on (5v,USB), j20 and j32 are jumpered: all led are green .Or Have I  to power j5 with 5v also in the case I use usb to power the ddc264evm ?

    Thanks in advance

  • If you scroll up you can see the suggestion that had been made to me concerning powering the board externally (not with the USB). doing that fixed the problem for me. I'm not sure if the powering with the USB actually works. 

  • so you have used usb for data and an external source to power the ddc264evm and inthis way  have you solved ?

    But have you try with only usb or you have try but You have verify that with only usb don't go ?

    Thank in advance

  • yes, by changing the jumpers appropriately, using the external power for both the analog and digital i got it to work.

    i could not get it to work powered only by usb.

    if you open up the  application and the text that says "daughter board" is red it means it's not appropriately connected. one of the previous comments outlines this

  •  Giorgio,

    We recommend powering the device from external power since it is the cleanest and most accurate source. In our lab we use J5 to supply the chip AVDD and J12 to supply the on board regulators and chip DVDD. We use two +5V supplies, one for J12 and one for J5. These two supplies are referenced to the same ground. We do not connect J16, it is not populated on our boards. Do you have the Analog Input Board connected to the EVM main board and biased from the J12 SMA connector? What are the jumpers on the AIB set to? If you would like you can send me an email directly on Adam.sidelsky@ti.com

    Regards,

    -Adam Sidelsky

  • Thank you Adam (David too). So the best thing to do is use J5 and J12  with the same source at +5V and remove the installed (by me) J16 and J19 ,J20 as write on the userguide and use usb cable only for collecting data. I have the AIB connected to EVM and J11 is on Vref meanwhile j1-j10 some are on vref and some no and some without jumper because I'am trying to understand how to obtain data from evm :leaving without jumper have caused some damage to aib or evm ?

    In a previuos post you have attach the xls document ddc264 evm channel mapping: so to be sure to have understood seeing table 3 page 6 on ddc264evm user guide on J1 there is R1- R28 and R1 map on U101 the channel 31 on AIB that is the channel 223A on evm so the R4 map on U201 the channel 1 on the AIB that is 129A on the evm ?

    Thank again

    Giorgio

  • Giorgio,

    Providing +5V on the EVM J12 and J5 is correct. Use the USB connection to collect data.

    VREF is the initial charge value of the internal DDC caps, if you tie the input to this same VREF, you will not see your input voltage provided to the AIB J12 SMA connector. The purpose of this device is to use the input current to each of the 256 channels to reduce the charge on the internal caps, the system measures the voltage change and calculates the input based on this. If you tie the input to VREF you will not see your input changing if your input conditions change. To measure the resulting current from the AIB J12 you need to put J1-J10 in the Vin position, towards the top edge of the AIB. The position of J11 on the AIB only connects to the inputs if J1-J10 are in the bottom position. J11 lets you tie banks of inputs to GND or to VREF. Please see page 39 of the EVM user's guide for the AIB schematic. There should be no damage to the DDC or AIB unless you input a wrong voltage to J12, meaning something greater than +10V or less than 0V.

    For the input mapping, please make sure you are comparing the chosen resistor to the AIB J13 to the EVM J14 connector. Therefore, AIB R1 connects to J13A's K2, which connects to the EVM J14A K2 pin on IN57 (U101), then using the excel mapping file, the GUI channel 249A/B. Please note that the A/B for each input is the same, A and B are parallel integrators on each input.

    Regards,

    -Adam Sidelsky

  • Thank you Adam your help is very useful for me. So is there no way to use ddc264evm with only usb ?. I say so because the usb solution is really easy and on the userguide of ddc264evm the usb is presented as a valid one and talking with you it doesn't this. I have done my first test with a laptop and when I have seen your post about powering I have redone the tests with normal pc desktop (yesterday) believing that the problems could be the current limiting of usb port of laptop but nothing is changing. From now I will use your advices because I have spent too much time with usb solution.

    Thank for all

    Giorgio

  • Someone have used USB_IO_for_VB6.dll in matlab and know how to use the open and close function/method ?

    On the pdf guide it use CCyUSBDEVICE that is defined in CyAPI.lib(c++ lib  ) and not in CyUSB.dll(c# library): they are library from EZ-USB FX3 SDK. How to load CyAPI.lib in matlab ? Or if someone use a different way to load USB_IO_for_VB6.dll in matlab could explain me ?

    Thank in advance

    Giorgio