CAPSENSE™ & MagSense Forum Discussions

Hello,

I am designing a product for medical liquid sensing and I am a bit lost in all your products.

My tank is about 20cm high, and I need a 1mm accuracy (so 200 divisions). My sensor PCB can be up to 3cm wide (so 20cm x 3cm for sensor).

The distance between the liquid and the PCB is 2.5mm PVC, 0.5-1mm air, and 1.5mm ABS.

I was wondering if you had recommendation on which product to use, and how many (segmentation of the sensors). I already have a microprocessor in my product and only need the sensing part (via like I2C).

Hi all! 

I have been trying to understand how grounding works with CSX reading section 7.5 of the Capsense design guide.  The section has good information, but I would understand better with a more visual approach. I have a few questions for the community:

1. Understanding Cfs (finger to electrodes) and CbodyDG (body to device ground)

Figure 1: physical representation of figure 7-32 in capsense guide 

From my understanding, Cfs and CBodyDG should physically be represented this way. Cfs would be mainly influenced by distance (C = A/d) between the finger and the Rx/Tx electrodes. Too little distance boosts Cfs, creating the Cfs > CbodyDG condition. But it also mentions that water drops and directly touching the electrodes can also increase Cfs. Do these conditions also have to do with a small distance between the Cfs plate (finger or water drop) from the electrode plate? Or is there another important factor that weight is to increase Cfs drastically?

2. Understanding Cfm (the virtual capacitance between Cm and the finger)

Figure 2: figure 7-32 in capsense guide

In this image, what does the node in the green circle represent? It seems as though 2 capacitors would be formed between a Tx and an Rx, but say if I would compare it with the finger drawing figure 1, there is only 1 capacitor as the Rx and Tx electrodes directly pair with each other. So how does Cfm work? Because we already have the pairing of Tx and Rx with the finger with Cfs, I am not sure of what it represents. In figure 1, would it be possible to draw the Cfm virtual capacitor to better visualize its effect on the system?

3. Understanding  current flow

If I am correct, the whole process of CSX is to measure AC current variations coming from the Tx electrode. A low IRx means a high impedance (capacitance) between Tx and Rx, and thus mean no finger is nearby. When a finger is nearby and pairs with Tx/Rx, do Cfm and CbodyDG actually create a closed circuit and we have electrons transferred from the user’s body to the PSoC? That is what Ibody represents?

Hi,

Referring to 7.4.10 of capsense design guidelines.

From the capsense design guidelines document and other resources I consulted, I believe I have read mixed indications and it has become unclear if I should include to the ground central point (mentioned above):

1. All of the PSoC's VSS pins (VSSA and VSSD)

2. The ground pins of all of the PSoC's bypass capacitors

3. all of the ground connections for components like leds directly connected to the psoc pins and located in close vicinity of the psoc.

The image below illustrates my question. I have a supply ground plane on top layer (not shown in image to see the psoc and other components) and no plane on the bottom around the psoc. I am not sure if the ground pins, bypass caps and other logic components need to be isolated from supply ground along with the CIntX and capsense ground.

It is puzzling because in the datasheet, they say VSS pin should be the central point for star connection,

but there is no VSS pin, only VSSA and VSSD on psoc4100s

Thank you for your constant support, I wouldn't have been able to learn to use capsense without you...

Could I use tuner.dll  with C# to make a customer tuner GUI ?

I don't know how to achive this  ,

Is there anyboy could instruct me ?

Thank you !

Hi,

why are Capsense touchpads the only widgets that support all of the gestures? It is not specified in the datasheet, I was wondering if it is just firmware specific and one could decide to develop the necessary firmware to detect those gestures from a different widget, or if there is something mechanically or electrically unique about the touchpads that make them specifically suited for this task, say at equal resolution (say 3x3 touchpad vs 9 individual buttons)

Thanks!

Hi,
on my last custom board, I only had a 5 pin SWD programmer connector, and another i2c connector to communicate with a psoc devkit

I believe there was no way to directly use capsense tuner with this board. However, for my next iteration, I would like to do so! I would like to know my options, but it is not very clear. Can I do it with a miniprog4 programmer? I also have CYUSB232 and CYUSB234 chips, I don't know if creating a usb connector is a possibility?

Thank you!

Is there any module marker or solution provider that Cypress works with? I'm looking for a turn-key solution provider for touch display products

Hi,

In an old forum post, it has been recommended to place a ground trace between the tx and rx segments if they are routed parallel to each other.

original comment from the post CSX Touchpad PCB guidelines

Placing ground near Tx/ Rx traces increases the self parasitic capacitance of the Tx / Rx electrodes. Also it helps in avoiding unwanted Cm formation in the traces. We want the Cm to be formed only in the region between Tx and Rx segments and not in the traces. Also CSX sensing method is independent on the parasitic capacitance of the Tx and Rx segments but depends only on the Cm between the two segments. We usually recommend placing a ground trace between the tx and rx segments if they are routed parallel to each other.

I am pretty sure they meant the segment traces (because otherwise Tx would couple to ground I believe), but just in case there is an aditional design guideline I could try, I want to make sure. I added green and pink ground traces to a pcb between the segments and segment traces of rx/tx. What was meant in the comment was pink or green?

Thanks!

hi,

now i use the PSoC Designed develop the CY8C20X34 capsense model ,this is i first use this IDE.

when i build the prj ,it show:

lib/csa_emc.asm

!E CSA_EMC.inc(19): no such mnemonic 'Wizard_was_not_called_after_place_rename_configuration_change_or_update_Open_Chip_Editor_open_Wizard_press_OK_button_and_generate_project'

make: *** [lib/obj/csa_emc.o] Error 1

make: *** Deleting file `lib/obj/csa_emc.o'

CE_9_TuningCSAEMC_withCY8C20x34 - 3 error(s) 0 warning(s) 18:00:50

what is "Wizard_press_OK_button",where can find it?

how to do?

Thanks & Regards-