In this paper, we present and evaluate a new approach to communicate with inter-integrated circuit (I2C) enabled circuits such as sensors over near field communication (NFC). The NFC-to-I2C interface was designed using a non-standard NFC command to control the I2C bus directly from a smartphone, which was controlling both, the read and write operations on the I2C bus. The NFC-to-I2C interface was reporting back the data bytes on the bus to the smartphone when the transaction was completed successfully. The proposed system was tested experimentally, both, with write and read requests to a commercial microcontroller featuring a hardware I2C port, as well as reading a commercial I2C enabled humidity and temperature sensor. We present experimental results of the system which show that our approach enables an easy interface between smartphones and external sensors. Interfacing external sensors is useful and beneficial for smartphone users, especially, if certain types of sensors are not available on smartphones.
This paper discusses the possibilities to measure the amount of light with the help of portable devices such as mobile phones and tablets. Focus is directed to the accuracy of the ambient light sensor on smartphones in order to obtain the illuminance indoors and the solar radiation level outdoors. In general, information on the ambient conditions is vital to improve the performance of solar chargers. For example, if users are able to allocate beneficial locations to deploy solar chargers inside buildings, up to 100 times more energy can be gathered during the same periodic time. Similarly, under outdoor environmental conditions, solar modules can be aligned better towards the sun to increase the possible amount of output power. We analyse the accuracy of ambient light sensors which are available in today's low-cost and upper-class smartphones. Additionally, we present calibration strategies for ambient light sensors in order to minimise the error between conventional measurement equipment and mobile phones.
In this paper we investigated the opportunities to improve the energy collection of solar chargers with the help of sensors on smartphones. We focused on the information of the ambient light sensor and the accelerometer in order to find suitable positions for solar modules. In particular under indoor environmental conditions, the location and orientation of solar chargers is crucial. If users are able to allocate beneficial positions for their chargers, the amount of power from solar modules can be increased up to 100 times. This is why we investigated the performance of sensors on smartphones, in particular in terms of their accuracy. We present experimental results obtained with the help of nowadays mobile phones and compare the measurement results against values which were collected with conventional measurement equipment under different light sources.
Abstract-This paper describes a technique for calibrating the internal ambient light sensor (ALS) in smart phones. The calibration process depends on Near-Field Communication (NFC). The system consists of an NFC core implemented in an Field-Programmable Gate-Array (FPGA) development platform featuring the NFC analog front end circuit. In the proposed system, the smart phone interacts directly with a reference ALS through the NFC device The direct communication is possible with the help of a custom NFC command that controls an InterIntegrated Circuit (I2C) master core in the FPGA. After the calibration process of the ALS in a smart phone is completed, the accuracy of the measurement is greatly improved. This is helpful to obtain precise information on the light intensity in indoor surroundings.
In this paper, we present a new approach to interrogate sensors using Near Field Communication (NFC). This approach utilizes NFC data exchange format (NDEF) to report the sensor data directly to a cloud service through a smartphone. The new advantage in this approach is that no smartphone application is needed to move the data from the sensor to the cloud. We also discuss advantages and disadvantages of this approach compared to earlier NFC sensor interrogation solutions.
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