Translation and Rotation of Images in Six Degree of Freedom Using OpenCV

I would like to share a small C++ function to translate and rotate images in 3D space in six degree of freedom (6 DoF). It also adjusts brightness and contrast. I use OpenCV library to perform some image processing.

• OpenCV Setup on Linux
• C++ Example for 6 DoF Image Rotation

Near Field Communication (NFC) Using PN7150RPIM

Using OM5578 PN7150 NFC controller with Raspberry Pi is discussed.

• Hardware Module
• Library
• C++ Example

Hardware Module

PN7150RPIM demo kit consists of PN7150 controller which is soldered on Raspberry Pi Interface board. It also includes NTAG216 a NFC card for testing [1]. There are three different versions of interface board for PN7150 NFC controller - Raspberry Pi interface, BeagleBone interface, or Arduino interface [2]. As illustrated in Figure 1, it only uses 6 pins - 3.3V, and GND for power, SDA and SCL for I2C, a GPIO input IRQ for interrupt, and a GPIO output for Enable pin. There is also an optional 5V power VANT.

Figure 1. PN7150 NFC Controller Board Pins.

The Raspberry Pi version is used as SBC interface for this discussion. Its connections to the header is shown in the following Figure [3].

Figure 2. PN7150 RPi Interface Board Connections.

Library

There is NXP Linux libnfc-nci software stack on GitHub that supports PN7150 NFC controller [4] which we will clone as follows.

$ sudo apt install autoconf automake libtool git pkg-config
$ git clone https://github.com/NXPNFCLinux/linux_libnfc-nci.git

Then, navigate into the directory and generate the configuration script. The machine should have automake, autoconf and libtool packages installed before running the script.

$ cd linux_libnfc-nci/
$ ./bootstrap

There are three options to generate the Makefile to map Linux NFC stack-

--enable-i2c

To use PN5xx I2C kernel mode driver which is default.

--enable-alt

To access GPIO and I2C resources from the user space in case the existing kernel offers access to them.

--enable-lpcusbsio

For USB devices implementing PN7150 with HID interface expose via LPCUSBSIO. protocol.

In our case, we will use --enable-alt option as the Raspberry Pi supports using GPIO and I2C through /sys/class/gpio and /dev/i2c-dev interface [5]. The stack is illustrated in the following figure.

Figure 3. libnfc-nci SW stack.

The i2c bus and GPIO pin can be configured in phTmlNfc_alt.h which is in ./src/halimpl/pn54x/tml/i2c directory. The existing values are

#define I2C_BUS "/dev/i2c-1"
#define I2C_ADDRESS 0x28
#define PIN_INT 23
#define PIN_ENABLE 24

Execute the following commands to generate the Makefile for the above settings, build and install the library.

$ ./configure --enable-alt
$ make 
$ sudo make install 

The install path is at /usr/local/lib. And for that you can use

$ export LD_LIBRARY_PATH=/usr/local/lib

or create config file as follows.

$ sudo sh -c "echo /usr/local/lib/ > /etc/ld.so.conf.d/nfc-nci.conf"

And load the configuration.

$ sudo ldconfig

C++ Examples

Example C++ programs to use NXP Linux libnfc-nci software stack as reader, emulator, etc. are also available on GitHub [6] which we will clone as follows.

$ git clone https://github.com/NXPNFCLinux/linux_libnfc-nci_examples

Then, you can navigate into an example directory, build, and run.

$ cd linux_libnfc-nci_examples/xxxx
$ make 
$ ./xxxx 

References

[1] NXP Semiconductors. PN7150 Raspberry Pi SBC Kit Quick Start Guide. 2019-07-08.
url: https://www.nxp.com/docs/en/application-note/AN11758.pdf.

[2] NXP Semiconductors. PN7150 NFC Controller SBC Kit User Manual. 2019-07-10.
url: https://www.nxp.com/docs/en/user-guide/UM10935.pdf.

[3] NXP Semiconductors. NFC's SBC Interface Boards User Manual. 2016-05-02.
url: https://www.nxp.com/docs/en/user-guide/UM10956.pdf.

[4] NXP Semiconductors. PN71xx Linux Software Stack Integration Guidelines. 2018-08-10.
url: https://www.nxp.com/docs/en/application-note/AN11697.pdf.

[5] NXP Semiconductors. Easy set-up of NFC on Raspberry Pi. 2018-08-14.
url: https://community.nxp.com/docs/DOC-341231.

[6] NXP Semiconductors. linux_libnfc-nci_examples.
url: https://github.com/NXPNFCLinux/linux_libnfc-nci_examples.

Zint Barcode Generator

Zint is a cross-platform open source barcode generating library which can be found at

https://www.zint.org.uk/.

You can get zint from the following github repository.

https://github.com/woo-j/zint.

• Zint Setup on Linux
• Simple C Example
• Manipulating Zint Image

PCA9535 GPIO Expander

PCA9535 is a GPIO expander with 16 IO lines which has I2C bus interface. It provides additional IOs for I2C bus master such as SBC or MCU that can be used to read push button or sensor, to control LED, etc. PCA9555 is identical to PCA9535 except the presence of internal pull-up resistor which increases power consumption when the IOs are low. PCA9535C is another variation of PCA9535 with open drain outputs. Its operating supply voltage range is 2.3V to 5.5V. There are 3 hardware pins which allow to use 8 different I2C bus addresses, from 0x20 to 0x27.

• Setup
• C++ Example
• Using Device Overlay

Software timers and Ring Buffered UART Com for LPC824 MCU

In this article, I would like discuss about using LPC82x MCU with MCUXpresso IDE. I will use LPCXpresso824-MAX Board as a hardware platform.

• Environment Setup
• SDK Example
• Soft Timers
• Com