Programming the Taida Century NRF52832 developer board

Its been a long hiatus regarding this post. At the time I’ve bought a generic eBay/Aliexpress nRF52832 development board (the Taida Century NRF52832 based board) for performing some BLE testing, did some development with Nordic SDK and the NRF Arduino firmware using Platformio, but posted nothing on my blog regarding the tests.
The main trigger for picking up again this board and do some writing about it, is that I’m evaluating RIOT-OS and its capability to target several hardware platforms, namely the NRF52 based chips. Anyway, first the use of the Arduino framework for the NRF52 and platformio:

Programming the NRF52832:
For programming the Taida Century NRF52 board need a programmer supporting the NRF52 chip, that can be either a SEGGER JLink programmer probe (highly recommended), or with a STLink V2 coupled with modified Openocd software, that also does work fine (Recent versions of Openocd already support the NRF52 out of the box). The Blackmagic probe is also an alternative, but since I have now a Jlink probe, never bother again with it.

The hardware connections for programming and debugging:
Since that the board does not have a serial to USB chip and a USB connection, an external TTL to USB serial convert must be used to see any serial output on the computer from the Serial.println commands. Furthermore the USB serial adapter must also must work with the 3.3V used by the NRF52. The 3.3v power can be provided either by the USB serial converter or by the debug probe (but not both at the same time!). I normally use a 6 pin CP2102 USB serial adapters: they work with 3.3v and have all the serial pins exposed.

The Arduino framework for the NRF52 board and specifically for the Taida board variant uses the following pins for serial communication:

RXD – Pin 18
TXD – Pin 19

So the TXD labelled pin on the USB adapter connects to the Pin 18 labelled header on the board (RXD), and the RXD pin on the USB adapter, connects to Pin 19 on the pin header on the board. Ground connects to ground. That settles the serial connection for debugging. The ground pin should also be connected either on the header pin labelled GND on the top left when the IDC connector is on the left, or on the IDC connector itself.

The connections for programming are a bit tricker depending if we are using an STLink programmer or a Segger Jlink programmer. In both cases the power can be provided by the programmer, but with the JLink one, a special connection is also needed so that the SWD debug lines voltage reference used is 3.3v instead of 5v.

Connecting the ST-Link programmer:
Since we are powering up the board from the programmer, and using one of those cheap st-link usb dongles, only four connections are needed:

The USB programmer has a 3.3v output and so can power up the board directly to the 3.3v board pin.

Connecting the JLink probe:
The Jlink probe can only provide 5V output on the JTAG pins, and so while the JTAG pins TCK and TMS can be connected to the TCK and TMS pins on the JTAG connector, the 5V pin must be connected to the VBUS pin on the IDC connector. This pin will provide power to the board and the internal regulator drops it down from 5V to 3.3V. To adjust the logic levels from the probe to 3.3V the JTAG pin VREF must be connected to the IDC pin 3.3V pin, that informs the JLink probe the device target working voltage.
So in total one more connection that with the ST-Link programmer.

The connection diagram is as follows, where the Taida board 12 pin IDC connector is used:

After the connection is done, we can test if we can communicate with the board using the JLinkExe:

JLinkExe -if SWD -device NRF52 -speed 4000
SEGGER J-Link Commander V6.44 (Compiled Mar  1 2019 17:36:52)
DLL version V6.44, compiled Mar  1 2019 17:36:42

Connecting to J-Link via USB...O.K.
Firmware: J-Link V10 compiled Mar  1 2019 16:57:49
Hardware version: V10.10
License(s): FlashBP, GDB

Type "connect" to establish a target connection, '?' for help
Device "NRF52" selected.

Connecting to target via SWD
Found SW-DP with ID 0x2BA03466
Found SW-DP with ID 0x2BA03466
Scanning AP map to find all available APs
AP[2]: Stopped AP scan as end of AP map has been reached
AP[0]: AHB-AP (IDR: 0x24770011)
AP[1]: JTAG-AP (IDR: 0x02880000)
Iterating through AP map to find AHB-AP to use
AP[0]: Core found
AP[0]: AHB-AP ROM base: 0xE00FF000
CPUID register: 0x410FC241. Implementer code: 0x41 (ARM)
Found Cortex-M4 r0p1, Little endian.
FPUnit: 6 code (BP) slots and 2 literal slots
CoreSight components:
ROMTbl[0] @ E00FF000
ROMTbl[0][0]: E000E000, CID: B105E00D, PID: 000BB00C SCS-M7
ROMTbl[0][1]: E0001000, CID: B105E00D, PID: 003BB002 DWT
ROMTbl[0][2]: E0002000, CID: B105E00D, PID: 002BB003 FPB
ROMTbl[0][3]: E0000000, CID: B105E00D, PID: 003BB001 ITM
ROMTbl[0][4]: E0040000, CID: B105900D, PID: 000BB9A1 TPIU
ROMTbl[0][5]: E0041000, CID: B105900D, PID: 000BB925 ETM
Cortex-M4 identified.

So the JLink probe works just fine.

The above did work, because the JLink probe is programmed to provide 5V power with the power on perm command.

Using Platformio to programm the board:

To program the board, it is necessary to specify correctly the Nordic SoftDevice and for that, the platformio.ini file needs special configuration, namely on the build_flags and build_unflags.

platform = nordicnrf52
board = stct_nrf52_minidev
framework = arduino
lib_deps = 259
build_unflags = -Os, -O1, -O2, -O3, -g1
;upload_protocol = stlink
debug_tool = jlink

With this file, any example from the NRF Arduino Library compiles.


fldigi slow startup on Linux

I installed fldigi on my ne laptop computer, with Arch Linux, and I hit trouble right away: The startup of fldigi on this computer was around 130s until the start command and the ui display. During that time one of the CPU cores hit 100% and stayed there. Not acceptable.
On my desktop computer, that is much older and has at least less than half the processing power of the new laptop, fldigi started up right away and I had no issues with CPU occupation.

It took me a while to find out the cause, and with the source code available (yay for open source) I’ve found the issue at the confdialog.cxx file specifically here:

Fl_Double_Window* ConfigureDialog() {
  Fl_Double_Window* w; 
  font_browser = new Font_Browser;

A lot of the time was lost inside the call to the new Font_Browser.

So I’ve checked the fonts installed on my new computer, and low and behold: 1248 more or less fonts !!! compared to 234 installed fonts on my desktop computer.

Comparing the Arch Linux packages that I had installed on one computer and on the other, the laptop had the ttf-google-fonts-git AUR package installed that added the bulk of all the fonts.

Removing this package solved the issue with fldigi startup delay. With the fonts removed fldigi started right away as soon I execute the command to start it up.

Self hosted mobile phone push notifications

Google cloud messaging (GCM), Pushbullet, among others, allows to notify users though their mobile phone or portable device for events that where trigger either, programmatically or by any other mean.

A nice self hosted solution that does not depend in form of third party services, and as far as I can see is being actively developed, is Gotify that offers a self hosted server, and mobile application for Android.

Gotify offers a docker images (and unfortunately in the last few days they stopped producing the Docker image for Raspberry Pi), that allows to have a running Gotify server in less than 2 minutes.

Anyway, I’m still running the latest docker image for the RPI. Since I have already running something at the HTTP port 80, I’ve started the Gotify container with an alternate port:

docker run -p 1080:80 -v /var/gotify/data:/app/data gotify/server-arm7

After docker pulls the image and starts it up, we can access the Notify Web Server interface at http://rpi:1080/ and access it with the default user/password admin/admin.

The first thing that we need to do is to change the default admin password and add an application. Both steps are straight forward.

The key aspect for the application after it is created is to take notice of the application token. This token will be necessary for inject messages on Gotify and associate the injected message to the application. Also there is the possibility to associate an icon to the application, that also be shown on the mobile application, by pressing the pen icon and adding an image.

After this, to inject a message from anywhere we can use CURL:

curl -X POST "http://rpi:1080/message?token=AhV-43qgmkKSj07" -F "title=RPI" -F "message=Status Alert"
{"id":16,"appid":2,"message":"Status Alert","title":"RPI","priority":0,"date":"2019-02-25T12:13:35.777531495Z"}

Anyway, to make things short, Gotify works more or less well. I still have some issues with the web interface and with the mobile application, but those issues might be associated to being using an older version of the server.

Synology reverse proxy and websockets
Gotify uses websockets as the transport medium for the push notifications.

As a final note, since I’m using the Synology reverse proxy to access the Gotify server from the internet, some special configuration must be done so that the Synology reverse proxy let’s websockets to “pass through” to the Gotify server.

Basically we need on to go to Control Panel -> Application Portal -> Reverse Proxy and create our rule that maps out the Gotify server to the external URL. I’ve create something like to be pointing to the internal Gotify server http://rpi:1080:

The important bit is that after creating the reverse proxy rule, we must edit and add the support for websockets by going to Custom Header and press the Create -> WebSocket button.

And that’s it. We have now a self hosted notification system. We can now, for examble, by using Node-Red or bash scripts, to start sending notifications to our clients when important events happen.

Lorawan/TTN with the TTGO ESP32 board

So I’m testing my TTGO Lora32 board with the RIOT-OS operating system to connect to the The Things Network, and while at first I had some success, then out of the blue things didn’t worked anymore.

The code that I’m using is based on the standard RIOT-Os Loramac example but with supporting code for ABP instead of the OTA activation.

The code is available at this Github repository.

Since I saw no activity on any channel for the Lora transmission by using the RTLSDR dongle, I suspected that something was up.
The Arduino based code from for connecting to TTN using Lorawan worked fine, and so it excluded an issue with the hardware.

By going to RIOT-OS installation directory, under drivers and on the sx127x directory, I’ve enabled on th sx127x.c file the debug to 1, since enabling debug on the semtech_loramac.c file held no useful information:

#define ENABLE_DEBUG (1)

With debug enabled, lo and behold, at startup:

2019-01-22 14:11:02,993 - INFO # [sx127x] error: failed to initialize SPI_0 device (code -1)
2019-01-22 14:11:02,993 - INFO # [sx127x] error: failed to initialize SPI

This is rather strange since at the initial tests the sx127x was detected and worked.
The only thing that changed is that I periodically update the RIOT local repository, and checking my board definition with other ESP32 boards that have a sx127x transceiver, the way that the pins where declared were quite different from what I had initially.

So I’ve changed the way that the pins for the SPI and the sx127x peripheral where defined, and the result:

2019-01-22 14:28:00,847 - INFO #  -> Node activation by: ABP
2019-01-22 14:28:00,847 - INFO # [sx127x] SPI_0 initialized with success
2019-01-22 14:28:00,848 - INFO # Set ABP information.

And the data arrives at TTN without any issue:

So either I had initially had the pins for SPI and the sx127x defined wrong or the latest RIOT build changed the way pins where defined.

A more complete example, working with multiple threads, is also available at this Github repository.

The ESP32 TTGO board using RIOT-OS

In the last few months, RIOT-OS operating system gained support for the ESP32 and ESP8266 based boards. RIOT-OS also supports several communication protocols, namely Lorawan through the usage of the Semtech implementation.

My post connecting the ESP32 TTGO board to TTN (The Things Network) describes (more or less) how to connect this board to the The Things Network using the Arduino and LMIC stack for the ESP32.

So why don’t give it a go with RIOT-OS?

Board definition:
RIOT-OS works with board definitions that describes several key features of the targeting board. In the case of the TTGO ESP32 Version 1 that I have several things needed to be changed from the base ESP32 board definitions that are available now on the RIOT-OS code base.

The most important issue was the clock speed definition for this ESP32 board, since it seems it uses a 26MHz clock instead of the standard(?) 40Mhz clock. Without the change for the clock speed all the serial output on the USB port was garbled and unreadable.

With the clock speed correctly set, important information regarding the pins for the I2C, SPI buses and the sx1276 chip needed to be defined. That was also correctly defined, and preliminary tests show that the Oled and sx1276 is detected using the Semtech Loramac stack.

I haven’t yet change the other pin definitions, so for the basic I2C, SPI, Button, and sx1276 are correctly defined.

The board definition can be found in my repository located at RIOT TTGO ESP32 repository under the directory boards.

To use this board definition, we just need to copy the board definition directory to the boards directory of the cloned RIOT-OS repository.

For testing we can just compile the examples under the example directory for the RIOT TTGO ESP32 repository.

There are two examples: One for testing the OLED screen and other to test the sx1276 and the Semtech Loramac stack.
This last example is based on the provided RIOT-OS example for Lorawan, but I’ve added support for ABP and debug prints to see what is going on.
On the Make file, we should select the type of activation and fill out the required data from the TTN device console. All data just needs to be copied and pasted directly and it should work.

To build the examples I’m using Docker according to this instructions.

Additionally, for the ESP32 flashing to work, the ESP-IDF repository must be cloned and its location set for RIOT build by setting the ESP32_SDK_DIR variable.

The following things work fine:

– The serial console works fine.
– The blue led, on and off
– The button, detecting it release and pressed.

The OLED works fine through I2C, but the I2C speed must be set exactly as defined on the board definition, otherwise it won’t work. It took me several hours to debug this issue.

The sx1276 works, it is detected and the Semtech stack seems to be able to use it. Adding some debugging to Loramac stack shows that the DIO# interrupts are detected but there are issues. For example I have two boards and with the same code I have different behaviours which seems rather strange… I was able to send data to the TTN gateway, but when waiting for the Semtech stack it hangs waiting for a stack status message. The other board is always complaining regarding MAC timeout.

So, all in all, as a first experience with RIOT-OS on the TTGO board, excepting the Lorawan stack, everything seems to work as expected. Regarding the Lorawan stack, probably going to try the LMIC Arduino implementation to see if it is possible to port it to RIOT-OS.

SDRPlay, CubicSDR on Arch Linux

This is just a simple post for writing the instructions for installing and using SDRPlay RSP1A (Should work for other versions) and CubicSDR on Arch Linux. I’ve previously installed most of the supporting software manually on my PC, and also had trouble installing the SDRPlay driver on Arch Linux with the SDRPlay installer on my PC. Since I have a lot of QRM (Noise) in my home, the next step was to use a portable computer to move the SDRPlay outside.

So, the following instructions are much more streamlined, since all the required software is on the AUR repositories, and so no “hacking” is needed.

Installing yay AUR package manager
If necessary we should install a AUR package manager. There are several ones, but as far as I’m aware, for now the yay is the currently maintained AUR package manager:

git clone
cd yay
makepkg -si

We can now use yay.

Installing CubicSDR with SDRPlay support:
If before installing CubicSDR we install HamLib support we will have a new menu on CubicSDR for rig control, otherwise it wont appear.
Then we need to install the SDRPlay driver, Soapy support and also CubicSDR.

yay -S hamlib
yay -S libsdrplay
yay -S soapysdr-git
yay -S soapysdrplay-git
yay -S soapyremote-git
yay -S soapyrtlsdr-git
yay -S cubicsdr-git

I’ve also added support for remote devices and the ubiquitous RTLSDR dongles.
CubicSDR will take a while (20 minutes, it will depend how fast is your computer) to compile, mainly because of the wxgtk widgets.

After it ends just connect the SDRPlay to the computer USB port, and execute CubicSDR. If the SdrPlay does not appear on the device list, press the Refresh button:

And that’s it, no fuss install, at least for me.

ESP32 TTGO board and Nordic Thingy:52 sensor device

The Nordic Thingy:52 is a 40€/50€ device based on the nRF52832 Nordic microcontroller that has, in a ready to use package, several environmental sensors, that can be accessed by low power Bluetooth (BLE). Nordic provides a complete solution that comprises the Thingy:52 firmware already flashed on the device (Source at GitHub) and an very nice Android Nordic Thingy:52 application, with also sources available at GitHub.

Anyway I have some of these devices for some months now, for other uses, but I decided to test the ESP32 based boards, since the ESP32 has Bluetooth and theoretically can connect and gather gather data from the Thingy. So this post is about the use of the TTGO ESP32 Lora based boards with an OLED to gather data, show it on the OLED, and send it to The Things Network. Seems simple, right?

So when a application connects to the Thingy:52 it can be notified when a sensor value changes throught the standard BLE notification mechanisms. The way the Thingy firmware works, this notification happens at a fixed intervals instead of a value change, and that interval, 5 seconds, 10 seconds, be defined by the Android App or programmatically by our application.

The application is developed by using the PlatformIO and for using the ESP32 Bluetooth interface, I’ve used the NKolban ESP32 BLE Library that happens to be library 1841 at the Platformio repository.

To cut a long story short, as still of today, the ESP32 BLE library doesn’t work correctly with the Thingy:52 notifications. This means that the application subscribes to have notifications, but those never happen. Fortunately someone already hit this problem and solved the issue, but the correction still hasn’t hit the library.

So basically to have my code example to work the following steps are needed:

  1. 1. Clone the TTGO ESP32 repository from . The repository uses the PlatformIO to build the application.
  2. 2. At the root of the repository run the command pio run so that the libraries are downloaded and installed.

At this point we need to correct the Arduino ESP32 library to add the patch to the notification issue.
Just execute the command:

[pcortex@pcortex:ESP32_NordicThingy|master *]$ cd .piolibsdeps/ESP32\ BLE\ Arduino_ID1841/src

At this directory (.piolibsdeps/ESP32\ BLE\ Arduino_ID1841/src edit the file BLERemoteDescriptor.cpp and at around line 151 (the exact line number will probably change in the future) we must change the ::esp_ble_gattc_write_char_descr function parameters:

 * @brief Write data to the BLE Remote Descriptor.
 * @param [in] data The data to send to the remote descriptor.
 * @param [in] length The length of the data to send.
 * @param [in] response True if we expect a response.
void BLERemoteDescriptor::writeValue(
        uint8_t* data,
        size_t   length,
        bool     response) {
    ESP_LOGD(LOG_TAG, ">> writeValue: %s", toString().c_str());
    // Check to see that we are connected.
    if (!getRemoteCharacteristic()->getRemoteService()->getClient()->isConnected()) {
        ESP_LOGE(LOG_TAG, "Disconnected");
        throw BLEDisconnectedException();

    esp_err_t errRc = ::esp_ble_gattc_write_char_descr(
        length,                           // Data length
        data,                             // Data
    if (errRc != ESP_OK) {
        ESP_LOGE(LOG_TAG, "esp_ble_gattc_write_char_descr: %d", errRc);
    ESP_LOGD(LOG_TAG, "<< writeValue");
} // writeValue

We need to change the highlighted line to:

    esp_err_t errRc = ::esp_ble_gattc_write_char_descr(
        length,                           // Data length
        data,                             // Data

With this change, the code at my github repositories has a working example:

– The ESP32 connects to the Nordic Thingy:52 device.
– It programs the Nordic Device to notify sensor values each 5 seconds (in real use cases it should be much larger period)
– Current sensor data is shown on the serial terminal.

What needs to be done:
– When notified by the Thingy:52, the ESP32 shows the new data on the OLED screen (WIP – Work in progress).
– To keep the application obeying the ISM bands duty cycle, it collects the data, calculates the medium, and sends the data to the Things network each 10 minutes (Also work in progress).