Cypress PSoC 6 and AWS IoT

A quick look at the new Cypress PSoC 6 boards and getting them connected to AWS IoT services

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Using mBed to create a simple MQTT application which logs ambient light sensor data to the AWS IoT Cloud

This project takes a look at using one of the two Cypress PSoC 6 wireless kits to connect to the AWS IoT cloud. Using MQTT with TLS, we then publish some data collected from a light sensor. The project goes step-by-step over getting AWS IoT set up (not an easy thing without instructions!) as well as modifying the example code Cypress provides to publish our collected data.


My modified version of publisher.cpp

x-c++src - 4.72 kB - 03/15/2020 at 23:40


  • 1 × CY8CPROTO-062-4343W Cypress PSoC 6 prototyping kit

  • 1
    Get your AWS account set up

    Amazon Web Services (or AWS) is a massive suite of services, including cloud servers, databases, DNS, machine learning, even quantum computing! Plus the service that is especially interesting to us -- IoT. Go poke around on their front page, and you'll see just how many services they offer. It's truly mind-boggling.

    While you're there, you can either create a new account, or you should be able to log in with your existing Amazon account credentials. Don't worry about costs yet -- AWS has their Free Tier which gives very reasonable limits you can use to try out their products. Some of these are limited to 12 months, including IoT, but it includes 250 000 MQTT messages per month, 3 devices (or "things"), 50 device commands per month (this includes device creation and remote management, which we won't be using), as well as 2 500 events per month (events are automatic reactions to messages that are sent from your things) and access to their graphing service. Pretty neat! If you plan to use it after 12 months, the prices are quite low, and there are other services besides AWS that are free -- but often they don't support TLS, and having the integration with other AWS services is nice.

    The downside of AWS, especially for first-time users, is its inherent complexity. Many of their services are tied together, and they often offer confusingly similarly named services that do different things. AWS really is targeted at enterprise users -- but that doesn't mean hobbyists can't use it too! You just need to be prepared to approach things in a methodical way.

    Side note: if you are joining AWS for the first time, be sure to check out the other services offered, especially the 12 months of a cloud server for free.

  • 2
    Create your AWS IoT Thing

    Now that you are logged in, head over to the AWS Management Console. At the top, click Services, and scroll down until you see Internet of Things on the right hand side. Click on IoT Core.

    On the left hand side, click Manage, and then click Create in the upper right. Choose "Create a Single Thing" and then give it a name. You can safely ignore everything else on this page for now. Scroll down and click Next.

    The next page shows certificate creation options. AWS IoT is only accessible via TLS, meaning we have to deal with private keys and certificates. If you were starting from scratch, this would be quite the speed bump, but luckily mbed and Cypress have provided excellent example code and libraries. Choose the top option, One-click Certificate Creation.

    This page is only ever shown once, so make sure to download all the files!

    Super important note! The next page that shows up will only ever be shown once, as a security measure. Make sure to download all three files: certificate, public key, and private key. After you have downloaded them, click the Activate button.

    Next is a super-important step that I skipped when I first started working on this project, and it caused me hours of headaches thinking something completely different was wrong.  Click Done, which should take you to the details page for your newly created Thing. Click the grey back arrow in the upper left hand corner.

    Now we need to create a policy and attach it to the thing we just created (remember when I warned you about how AWS is targeted for enterprise usage? Now you can see I wasn't kidding!). On the main IoT Core page, click Secure in the left-hand menu. This will open a sub-menu where you can see the certificate we just created. Below Certificates, click on Policies, and then click on Create in the upper right. Give it a name like "Open". In the statements section below the name, enter iot:* as the action, and * as the resource ARN. Check off Allow, and then click Create at the bottom right.

    This is what should be entered when creating your policy

    Now go back to the Certificates sub-menu, and click the three dots in the certificate box. Choose Attach Policy, check off the policy we just created, and click Attach! Now we are finally ready to cloud surf.

  • 3
    Getting set up with mbed

    mbed is a service offered by ARM. It's essentially an online IDE with support for many different microcontrollers that use ARM cores. The Cypress boards I am using have landing pages at and which give some info about the features of these boards, as well as links to schematics and other board data. Cypress also has a bunch of code examples on mbed, including the one that I based my code off of, which is located here:

    The CY8PROTO-062-4343W development board

    If you click the Import into Compiler button in the top left, it will copy that code into your mbed workspace. This example contains two different programs, one for publishing and one for subscribing. For this example we will only be publishing, and the compiler seemed to get confused with both folders present, so I deleted the subscriber folder. 

    Note: If you end up using the mbed command-line tools instead, it's not necessary to delete the subscriber folder. Simply issue the command "mbed config root ." It's also helpful to set the board you are using, which you can do with "mbed target cy8cproto_062_4343w" or "mbed target cy8ckit_062_wifi_bt". Note these names use underscores, not hyphens!

    The first and most critical step to getting this example working is to set up your AWS credentials in the aws_config.h header file. I will go through each item in this file, and explain exactly what you need to put in each.

    1. AWSIOT_ENDPOINT_ADDRESS: This is the actual address that your thing will communicate with. You can find it in the IoT panel by clicking on Manage, then clicking on your Thing. Select Interact from the left-hand menu, and then copy and paste the URL under the HTTPS heading. It will end in
      Here is where to find your endpoint URL
    2. AWSIOT_THING_NAME: This is the human-readable name you gave your thing when creating it back in step 2. I just called mine "Cypress" but just make sure it matches whatever name you gave it in AWS.
    3. AWSIOT_TOPIC: This is the name of the topic it will publish to. This can be anything you like, as long as you remember it!
    4. const char SSL_CLIENTCERT_PEM: This is the certificate file that we downloaded earlier. It needs to be formatted in a particular manner, as shown in the example section. Copy and paste the entire file between the quotes, and then format it as shown. You will need to put quotes around each line, as well as add \n to the end of each line. You also need a backslash as the last character on the line. I will include a redacted screenshot of what mine look like.
    5. const char SSL_CLIENTKEY_PEM: This is the private key file that we downloaded. It needs to be formatted exactly as above.
    6. const char SSL_CA_PEM: This is the Amazon AWS root certificate, available at Make sure to copy and paste the entire thing, and format it the same was as the other two.
    This is how your keys and certificates should be formatted

    The last thing we need to do before launching the example code is adding our Wi-Fi credentials to the mbed_app.json file. Replace the SSID and password with your details, making sure to leave the escaped quotes in place. It should look like this:

        "target_overrides": {
            "*": {
                "platform.stdio-convert-newlines": true,
                "": "WIFI",
                "nsapi.default-wifi-security": "WPA_WPA2",
                "nsapi.default-wifi-ssid": "\"MyNetwork\"",
                "nsapi.default-wifi-password": "\"password123\"",
            "platform.stdio-baud-rate": 115200

    With all that inserted, you should be able to compile the example code. This will create a .hex file that will be automatically downloaded. Save it somewhere, and then plug your board in to your PC. If your board does not show up as a USB drive, read the instructions below on how to get your board's firmware updated. Otherwise, drag the downloaded .hex file into the USB drive that appears, and the firmware will self-program.

    Cypress have released a tool to update the firmware on their boards. By default, these boards come with KitProg2 installed, but we need KitProg3. Download the latest release from their GitHub repository depending on which OS you run, and unzip it. Connect your board, and navigate to the bin/ folder inside the extracted folder. Run

    fw-loader(.exe) --update-kp3 all

     and allow it to finish. Once this is complete, you can either push the button on the programmer portion of the board labelled "MODE" to get it into DAPLINK mode. Or, you can simply run

    fw-loader(.exe) --mode kp3-daplink

     and it should appear as a USB drive. From now on, all you need to do to update the code running is simply drag and drop the downloaded .hex file into the USB drive. It will automatically self-program and then delete the .hex from the USB interface.

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William Williams wrote 06/06/2020 at 03:51 point

@Alexander, Bigly Thanks!!! Saved me countless hours of reading and trial and error, I am publishing and subscribing, sending commands to my device via IoT Core!


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Alexander wrote 07/02/2020 at 05:09 point

So glad this helped you out! Sorry I didn't see your first comment!

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William Williams wrote 06/04/2020 at 05:54 point

I am dealing with an issue I’ve not ever seen. When I send a dummy byte I expect the value to be returned to me. In fact, I did just that, val = Cy_SCB_SPI_Write(). I kept getting a 0x01. The reason I found, is because Cy_SCB_SPI_Write() returns how many data elements were placed in the TX FIFO.

So I have to do a Cy_SCB_SPI_Read() following the Cy_SCB_SPI_Write().

The Cy_SCB_SPI_Read() further notes:

This function only reads data available in the RX FIFO. It does not initiate an SPI transfer.

When in the master mode(which I am in Master Mode), this function writes data into the TX FIFO and waits until the transfer is completed before reading data from the RX FIFO. (WAIT, WHAT... I do not want you to write anything to the TX FIFO!!! That doesn't make a bit of sense!!!)

So I Cy_SCB_SPI_Write(read register) ignore return, Cy_SCB_SPI_IsTxComplete(txfifo empty) tx complete, Cy_SCB_SPI_Write(dummy to push return to rxfifo), val = Cy_SCB_SPI_Read() to get value from RxFIFO, all I ever get is 0x00000000.

So I turn power off to the SPI device I am trying to interface, MAX14830, I do the operations above, I do a Cy_SCB_SPI_GetNumInRxFifo() and it returns a one (1).



The number of data elements in the RX FIFO. The size of a data element defined by the configured RX data width.


This number does not include any data currently in the RX shifter. (So, I ponder if my data is in the shifter...)

Remember I powered off the MAX14830... So...



The number of data elements placed in the TX FIFO: 0 or 1.


When in the master mode, writing data into the TX FIFO starts an SPI transfer.

So I have to assume, the Cy_SCB_SPI_Write() does a SPI transfer shifting 0x00000000 into the RxFIFO (MAX14830 is powered off). I still am trying to figure out why the return value is uint32_t when I designed the SPI SCB as 8bit wide, but that is the least of my worries... As you can probably tell I am sitting beside myself, dazed and confused and lost. And two weeks behind trying to explain to my project designator and project engineer why I can’t do something so basic...

Have any of you come across this? I am using PSoC Creator 4.3 PDL .3.1.1...

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Sergey wrote 05/02/2020 at 13:14 point

Nice project! Please note, that pins P10_1 and P10_2 on the CY8PROTO-062-4343W are connected to a thermistor. So your measurements of ambient light will be affected by the temperature as well.

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