PSoC4000s & CSX Mutual CapSense Buttons Part 2

In the previous post I gave you the instructions to get the new Mutual Capacitance buttons going on the CY8CKIT-142.  In this post I will talk about how to add the Capsense Tuner to your project.  The Capsense tuner can talk to your design while it is running, then report back to you the parametric of your design.

First you need to add the tuner to your project.  In order to do this, start with the last design, then add an EzI2C component.  Here is the new schematic:


Then you configure the EZ2IC to have 16 bit sub addresses.


Then assign the EZI2C pins to the KitProg I2C bridge pins


The last step is to write the firmware which is almost exactly what you had in the last project except

  • Lines 8-9 which start the capsense block and setup the Capsense memory buffer to be readable by the remote host
  • Line 21: which updates the Capsense memory buffer with the current state of the capsense parameters


Once all of this is done, build and program the device.  Then start the capsense tuner by right clicking the Capsense component in the schematic and saying “run Tuner”


Then configure the tuner communication parameters from the “Tools->Tuner communication setup” menu.  These should match what you have setup in the EZI2C component.  Specifically you need set the I2C addresses to be the same, and you need to have the sub-address set to “2-bytes” which is the same as the 16-bit sub-address which you set in the component above.


The next step is to press “connect”  and the “start”.  First make sure that your three buttons are working.  In the picture below you can see that I am touching Buttons 1 and 2 as they are “active” (red color) which means that their signal is above the threshold.


The next step is to look at a “graph view” of button 0.  You can do this by pressing “graph view” and selecting Button0_Rx0.  Once I switch to this view I touch the button 9 times.  You can see that as there are 9 button touches in the Status window.  A status of 1 means that the button is active and a status of 0 is an inactive.

In the sensor data window you can see the “baseline” which is the noise on the sensor node without a touch.  The blue line is the “RawCounts” which the amount of signal on the node.

In the middle window you can see the “Sensor Signal” which is the Sensor Data minus the baseline.  Any time the Sensor Signal is above the touch threshold then the sensor status is active.


The last step is to use the SNR measurement tab to see how robust your design is.  First click on the “SNR Measurement” tab.  Then pick out which sensor you will measure.  In this case I have setup measurement on “Button_0”.  Then click on “Acquire noise” and wait.  It will make the graph shown below which says that my noise is about 3008-2995 or about 13 counts.


The next step is to see how much signal you get.  Start this process by pressing “Acquire Signal” and touching the correct button.  You can see orange line represents the amount of signal when you are touching the sensor.  The system will then calculate the SNR which in this case is 56.85 which is tons.


The last thing that you could do is change the Capsense parameters in the sensor parameter screen.  For instance you could change the threshold from 100 to a bigger number to give more reliable touches.


OK.  Now I have my capsense buttons working.  In the next posts Ill be ready to talk more about the Smart IO.

You can find this PSoC Creator workspace on github in the directory called “145MutualCap”.  This project is called “TunerMutualCapButtons-145”.

PSoC4000s & CSX Mutual CapSense Buttons Part 1

In the previous post I talked about my original goal to learn about the SmartIO.  But, in order fully try out the SmartIO I needed an input source.  On this board I had only one easy input from the factory – specifically the mechanical button on P0[7]- but I wanted to have multiple switches.  Well, the obvious choice was to use the three Capsense Buttons on the user interface expansion board.   When I looked at that board closely I remembered that the buttons were put there to support the new Capsense functionality of the PSoC4000s family.  Inside of Cypress we call the new feature “CSX”, but its real name is “Mutual Capacitance”.  Mutual Capsense works by transmitting a signal on the “Tx” pin and then receiving that signal by capacitively coupling that signal through your finger into the “Rx” line.  Here is a picture of that part of the PCB schematic and a zoom in of the board.  You can see that there are three different size buttons.  Each of the buttons is composed of an even number of pie shaped segments.

mutual-cap-buttonsScreen Shot 2016-03-06 at 2.03.17 PM

The mutual capacitance technique has a much higher Signal-to-Noise Ratio (SnR) as compared to the Self Capacitance technique of previous chips and as a result is more immune to noise and can work through a thicker overlay.  I thought that I would try putting on overlay on my board, so I cut out a piece of 1.5mm acrylic and used double sided tape to attach it to my board.  You can see it in the photograph above.

To make this work I started by creating a new project called “MutualCapButtons”.  I then added the Capsense component and three digital output pins (one for each of the three LEDs on the expansion board).  Here is the schematic:


The next step was to configure the CapSense block by double clicking it.  I then added three buttons and set the sensing mode to CSX (Mutual-cap).


It is possible to have dedicated Tx/Rx pins or you can share the Txs.  To do this, select “Advanced” and “Widget details”.  Then select “Button1_Tx”  and choose its sensor to be the same as “Button0_Tx”.  On this design I shared the Tx between all three of the buttons.


The next step is to assign the pins to the correct Port/Pin locations on the chip:


The last step is to write the firmware

  • Lines 8-10 Start the capsense block and get the scanning going
  • Line 14: If the capsense block is done scanning then process the results
  • Line 16: Take all of the raw data from the scan and setup all of the status information
  • Lines 18-20: If the buttons are being pushed then turn on the corresponding LED
  • Lines 22-23 Start another scan


That is all there is to making it work.

You can find this PSoC Creator workspace on github in the directory called “145MutualCap”.  This project is called “MutualCapButtons-145”.

In the next post Ill talk in detail about using the Capsense Tuner to understand the Capsense performance.

PSoC4000s & The SmartIO – Part 1

In the previous four posts I talked about building an IOT device using the new CY8CKIT145.  You might remember from the first post that my original objective in picking up the board was to try a new feature of PSoC Creator.  Well, over the last few days I have been trying out that feature. Actually, it isn’t a feature of the software, it is a feature of some of the new chips called the Smart IO.  The Smart IO is a programmable logic bock that sits between the High Speed IO Matrix (HSIOM) of the chip and the Input/Output Port.  The HSIOM has all of the peripherals (SCB, TCPWM etc) of the chips attached to it.  The Smart IO will allow you to take signals from inside or outside of the chip, perform logic functions on them, and then drive those signals into or out of the chip.  Some of examples of why you might want to do this include:

  • Combining several inputs (from the outside) to trigger an interrupt
  • Inverting a signal entering the chip
  • Inverting a signal exiting the chip
  • Remapping an input from one pin to a different input (e.g. flipping Tx, Rx pins)
  • Buffering one signal into multiple output pins (to increase the drive strength)

As usual with Cypress programmable logic, you can do a jaw dropping number of clever things.  This block includes sequential logic as well as combinational logic, so it is possible to make state machines in the fabric.  It also includes more surprises which have not been shown yet.

The Smart IO works the same as other peripheral blocks, you start by dragging the component onto the schematic and double clicking to start the customizer.

When you start the customizer you get the screen below.  The first thing to decide is which Port is going to use the Smart IO.  The Smart IO completely takes over an entire port.  On this chip there are two Smart IOs, one on Port 2 and one on Port 3.   When you look at the customizer there are some things to notice:

  • On the right side of the customizer you can see the 8 GPIO pins.  The dropdown menus that are currently labeled “Bypass” allow you to select the mode of the pin (Bypass, Input, Output, None).
  • On the bottom of the customizer you can see the 8 LUTs and select their inputs.
  • On the left side of the customizer you can see the the 8 connections to/from the HSIOM.  The drop down menu that is currently labeled “Bypass” allows you to select the mode of that connection to the HSIOM (Bypass, Input, Output, None).   I will talk about the “Undefined” menu in the with the next picture
  • In the middle of the customizer is the routing matrix.  Horizontally on the routing matrix there are 8 groups of three wires.  The top wire in each group is a wire that originates with the GPIO.  The middle wire originates from the corresponding LUT.  The bottom wire originates from the HSIOM.  For example the top three wires in the picture are
    • Line 1: from GPIO7
    • Line 2: from LUT 7
    • Line 3: from Data7
  • You can “make” the connection by either by clicking the solder dot or by choosing from the coresponding drop down menu (more on that below)


The other menu on the HSIOM side of the customizer says “Undefined”.  This menu has a list of each fixed function device and the inputs/outputs of that device that can be connected to that input/output.  This menu doesn’t actually change anything in your design, it is only for information.  For example you can see in the screen shot below that  data4 can connect to:

  • TCPWM0: Line_Out
  • LCD0: COM[20]
  • LCD0: SEG[20]
  • SCB1: Spi Select[1]


The best way to show you how all this works is with an example.  One of the frustrating things for me in the PSoC 4 Family has always been that the fixed function blocks (TCPWM, SCB) are only allowed to connect to a few pins on the chip.  This can be a bit of a pain if you have a board that is already wired and you need to remap a pin.  Take for example, on the Cy8CKIT-145 the user LED on the main board is connected to P2[5].  If I want to drive that LED with the Line out (instead of the Line_Out_N) I would create a schematic like this:


When I go to the DWR to assign the pins I would see that the BlueLED cannot be attached to P2[5].  You can see all of the legal placements of that pin because they are highlighted in green.


If I try to do it anyway, I will get the following error when I build.


This error says that I cannot connect the “line” output of the TCPWM to P2[5] (the pin with the LED).  That sucks.  But, with the Smart IO, I can “remap” the TCPWM Line output to P2[5].  To do this, I will start with a by adding a SmartIO to my schematic and configuring it.

  1. Select Port 2
  2. Configure GPIO 5 to “Output”.  This can be done by either clicking on the “solder dot” or by selecting output from the drop down menu
  3. Select data 4 as “Input”
  4. Select data 4 as “TCPWM[0].line.  Remember that this is ONLY for your information and doesn’t actually change anything in the project.
  5. Select the 3 inputs to LUT5 to be the data4 line which can be done from the three drop down menus or by clicking the three corresponding solder dots.

Screen Shot 2016-03-06 at 9.53.10 AMNext, I configure the LUT to “passthrough” by setting up 000 = 0 and 111=1 (which are the only two possible combinations as the three inputs are tied together).  You change the “Out”s from 0->1 and 1->0 by clicking on it.


Then I will re-wire up the schematic to look like this:


The firmware is trivial,  just start the PWM and the SmartIO


When I program the kit the blue LED starts blinking.  Cool.

In the next posts I will teach you how to use some other configurations of the Smart IO and how to use the CapSense block to create inputs for the Smart IO.

You can find this PSoC Creator workspace on github in the directory called “SmartIO”.  This project is called “SimpleSmartIO”.

Index Description
PSoC4000s & The SmartIO – Part 1 An introduction to the SmartIO and first project
PSoC4000s & CSX Mutual CapSense Buttons Part 1 Using mutual capacitance
PSoC4000s & CSX Mutual CapSense Buttons Part 2 Using the CapSense tuner
PSoC4000s & The SmartIO – Part 2 A 3 input XOR logic gate
PSoC4000s & The SmartIO – Part 3 A 3 bit up counter state machine
PSoC4000s & The SmartIO – Part 4 Using an external clock with the Smart IO
PSoC4000s & The SmartIO – Part 5 Triggering an interrupt

PSoC4000s and the CY8CKIT145 Stamp Board – Part 4

OK.  We’re ready for the big moment: the user test.  I was feeling pretty cool.  I had spent the week talking to 100s of people and putting on a pretty good show.  I was the master of all things PSoC, a geek rockstar.  So I programmed the firmware.  The slider worked.  I was able to connect to the PRoC BLE from my app.  But for some stupid reason the the PSoC and PRoC just were not talking and I had no idea why.  And to make matters worse, I didn’t have anything I could (easily) use to debug the problem.   So much for being the king of PSoC.  I assumed that I had firmware bugs. I tried a bunch of different things, single stepping code, trying different pins, etc.  But nothing worked.  I couldn’t figure it out.  It was intensely frustrating to be stuck on the airplane with a broken design.

As soon as I landed in Detroit, I logged in to get my email.  I looked for messages from Rajesh (the PSoC Kit Manager) and sure enough, he had emailed me the missing schematic.  After digging through the schematic, I found the error.


The connection between the PRoC and PSoC had a 0 Ohm resistor that was “No Load,” meaning the footprint was there, but the board manufacturer had not put on the resistor.  This was done so that the pin could be used as a GPIO for something else.

Here is a zoomed-in picture of the PCB:


The good news was, I was only one plane ride and an hour drive from my soldering iron.  As soon as I walked in the door, I went straight to my lab.


Now everything works.

There are two morals to this story:

  1. Don’t go to immediately to your lab after being gone for a week, as it really irritates your wife.
  2. Look closely at the schematic.

You can find the PSoC Creator workspace on github in the directory called “capsenseble-145.”

PSoC4000s and the CY8CKIT145 Stamp Board – Part 3

In this post, I will take you through the PRoC BLE schematic and firmware.  I describe a very similar version to this in great detail in the video you can find on the Cypress Video Training website.

First, I create a new project in my workspace called “145capsenseled-ble.”  Then, I add the UART component (the SCB version) and the BLE component.


Next, I configure the component to be a GATT server with a custom profile and a GAP client.


Then I create a custom service with two characteristics:

  • The “led” characteristic, which is set up as a uint8 that is writeable and readable.
  • The “capsense” characteristic, which is set up as uint16 that is readable and has a “notify.”

Next, I configure the UUIDs of the service and characteristics to match what is hard-coded in the iOS app.  Then, I add “Client User Descriptions” that describe the characteristics in plain text.


Next I configure the GAP settings, specifically the advertising packet.


I make the pin I assignments, which is just the UART Rx and Tx lines.


Finally, I write the firmware.  I started with main.  In the infinite loop (line 116), if I have received a byte from other side, then I assign it to the global variable “fingerPos” (line 118). Next, call updateCapsense() (line 119), to update the GATT database with the new value of the slider.


The updateCapsense function:

Lines 31/32 If there is no connection, then don’t update the GATT database.

Lines 33-39 Update the GATT database with the current fingerPosition.

Lines 42-43 If the iPhone side has asked for notification and the position has changed, then send a notification.

Line 44 Save the last position.


The BleCallBack is the most complicated section of firmware.  It uses a “switch” statement to handle the different event “cases.” The cases are:

  • CYBLE_EVT_STACK_ON & CYBLE_EVT_GAP_DEVICE_DISCONNECTED:  In either of these cases you want to start the advertising function.
  • CYBLE_EVT_GATT_CONNECT_IND: When there is a connection made, update the GATT database with the current state of the CapSense and the LED.  This allows the iOS side to read the correct values.
  • CYBLE_EVT_WRITE_REQ: There are two kinds of write requests that are valid.
    • CYBLE_LED_CAPSENSE_LED_CHAR_HANDLE:  If the remote side writes into the LED value, then send that data to the PSoC4000S via the UART.
    • CYBLE_LEDCAPSENSE_CAPSENSE_CAPSENSECCCD: If the remote side has been asked to notify (or un-notify), then save that in the global variable capsenseNotify.


That is all of the firmware.

In the next post, I’ll take you through the debugging I had to do.

You can find the PSoC Creator workspace on github in the directory called “capsenseble-145.”

PSoC4000s and the CY8CKIT145 Stamp Board – Part 2

In the previous post, I unboxed the CY8CKIT145 and showed you the schematics.   In this post, I will show you how to build the CapSense firmware that runs on the PSoC4000S.  The first decision I needed to make was how to connect the PSoC and the PRoC chips.  So I looked at the back of the kit and there was a handy-dandy picture of the schematic in the silkscreen.  Here is a zoomed in view:


I didn’t have the schematic on the airplane, but here is a more “schematic” view of the chips on the board.




I knew that the UART source code would be slightly easier, so I picked that as the mechanism to connect the chips.  On my computer I had the “capsenseled” workspace from the videos.  So, I created a new PSoC4000S project in that workspace called “145capsenseled.”  I started with the schematic:

  1. Add the new CapSense component.  I am currently running a “nightly build” of PSoC Creator 3.3 that supports the new chip.  You can see in the PSoC Creator release I’m using there is a prototype version of the CapSense component.
  2. Add 5 Digital Output Pins under software control to drive the LEDs that are next to the slider
  3. Add 1 Digital Output pin to drive the blue LED
  4. Add a Serial Communication Block (SCB) configured as a UART


Here is a screenshot of the new CapSense component configuration wizard.  You can see I added a linear slider and set up the component to use SmartSense full-auto tuning.


After configuring the CapSense, I set up the pin assignments using the DWR:


Then I wrote the firmware, which was pretty straight forward.

  • 10-11 start the CapSense
  • 12 start the UART
  • 16: If the CapSense block is done scanning and is idle, then read the CapSense and do something with it (lines 17 -> 41).
  • 18: figure out where the person is touching
  • 19: if they have actually touched the block
  • 22-26 light up the LEDs
  • 30-35 If there is no touch, then turn off the LEDs.
  • 36-37 start the next scan
  • 38-39: If the UART is not busy… then send the position (0-100) or (0xFF if there is no touch).
  • 41-42: If there is a byte in the UART receive buffer, then light up or turn off the Blue LED. (Notice that the LED is active low so I use the “!” operation to flip the state of the signal.


After that, I programmed the kit and tested it.  It seemed like everything was good.  In the next post, I’ll show you the schematic and firmware that runs on the PRoC BLE.

You can find the PSoC Creator workspace on github in the directory called “capsenseble-145.”

PSoC4000s and the CY8CKIT145 Stamp Board – Part 1

One of the cool things about my job is I get to try out lots of new development kits before they are released to the general public.  In the previous post I talked about the demonstration I gave at the Embedded World conference using the CY8CKIT-042 BLE.  You can find a complete video tutorial for that project on the video tutorial website.  While I was at the conference, I picked up an engineering sample of a new development kit and put it into my backpack because I wanted to try a new feature of PSoC Creator on the way home.  But, when I got on the airplane, I thought I would build the same project I had demonstrated at the conference using this kit.  So, in the next few posts, I am going to show you the new CY8CKIT145 Stamp Board and how to build an IOT solution with it.

It is called a “stamp board” because it comes in a flat postage stamp-like postcard mailer.  Here is a picture of the front and the back (you can see that it has already lived a hard life riding around in my backpack).


Here is the back of the mailer:


In the picture you can see the yellow label proclaiming this to be an engineering sample.  It doesn’t seem like much, but when you pull back the front of the package you get to see the surprise:


The kit can literally be broken into four separate pieces:

  1. The main board:
    • The PSoC4000S
    • A reset switch
    • A user LED
    • A user push button
    • A programming selector (to pick either the PSoC4000s or the PRoC BLE (that is on the back of the kit)) as the target of the programmer
    • All of the PSoC4000S pins are available on the 100mil center headers
    • A PCB footprint for a 10-pin ARM programming header
  2. A programmer board:
    • A PSoC5LP programmed with KitProg2 Firmware
    • A programmer mode button
    • 100mil center header with some of the PSoC5LP pins
  3. A Capsense slider user interface board with a 5 Segment Slider and 5 LEDs
  4. A Capsense button user interface board with 3 mutual capacitance buttons and 3 LEDs


And the back, with the tiny 10mm X 10mm PRoC BLE module:


Here is the schematic for the board:


CY8CKIT-145_PSOC_4A-S1 page 2


I wanted to build a project that would have two-way communication between my iPhone and the board, and would be compatible with the Swift App I had written.  The user of the board would have a capsense slider (and LEDs) of which the iPhone App could read the position.  In addition, it would have an LED that the iOS app could turn on and off.  Here is a demonstration that I filmed with my iPhone on the airplane:

In the next post I will describe the overall system and show you the firmware.