Use SPI port on raspberry PI

SPI is a frequent way to interface slave device with a micro-controller / cpu. SPI is a 4 wires synchronous connection between a slave and a master. As part of the 4 wires, there is a CLK signal, the speed is not defined and depends on the slave but it is usually > 10Mhz. SPI allows fast data transfer. Two data signals (MISO and MOSI) for Master (In/Out) Slave (In/Out) are used to transfer data in sync with the CLK clock. The last wire is a chip select signal named CEx for Chip Enable. As you can manage multiple slave, you have to manage different CEx signal, one per slave.

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Create a controlled 12V output for Raspberry Pi

I had to add a 12V controlled output for my raspberry Pi to connect a radio frequency system to my Pi. This system just need 12V to start transmitting but it needs 12V ! The raspberry can offer 5V or 3.3V. The solution is to use a currant elevator system. The one I built is based on a Texas Instrument component TPS6734, able to deliver 120mA / 12V with a 3.3V input.

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Control a high power circuit with arduino

irf9540I had to control power on an external circuit using an Arduino. the objective was to delay the power-on of a device consuming about 3A. One of the solution is to use a relay but it is a quite expensive solution another one is to use a Mosfet. This is the solution I’ll describe here.

 

 

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making a 5V – 3/4 A power supply for car

car_alimFor one of my project, I needed to have a >3A power supply to put in my car, delivering stable 5V. For this I tried different power supply from ebay used for phone & tablets. One of them was not so bad if you connect it after engine start. The main issue with these power supply is the poor quality of the filtering and engine start spike cancellation. As my circuit is sensitive to this spike, I decided to build my own power supply.

Here is the summary of this experience … click next !

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Arduino AtMega328p low power consumption

For one of my projects, I want to have a really low power consumption device to be able to use a battery for many month. For this I implemented a low power solution as described here. I’ll try to simplify it a little bit and document it a little more …

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Add a HC-05 standard bluetooth port to a RFDuino (BLE)

 

RFduino connected to HC-05 bluetooth

RFduino connected to HC-05 bluetooth

I was looking for a system able to work with an iPhone (Bluetooth Low Emission – LBE) and a standard android (Standard bluetooth / rfcom). The RFDuino Arduino platform I have is perfect for BLE so, I decided to add a HC-05 module for the standard bluetooth.

 

Here is the description on how to make it !

 

 

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Small ODROID-U3 platform coming out !

Really interesting tweet I just saw about the Odroid-U3 platform you can find following this link. This platform with the size of a Raspberry PI board is a 4 ARM core 1.7Gb (cortex A9) with 2GB included. Video is HDMI 1080p.Storage is MicroSD slot. The price is really low : 58$

You can ran even Android & Linux on it.

Compared to a RPI, this sound good for video/media box applications, better than RPI. For hacking this is largely different, as you can see on the picture, GPIO connector are not so easy to access. But, you can also purchase an extension shield providing all what you are expected with 36 GPIO. To build your own shield it could be more complicated than RPI. This let me go to a question I have since months … Why RPI is not becoming less and less expensive or more & more powerful ? it have now about 2 year old.

Less negative point : like any new board coming after Raspberry, the ecosystem is actually really smaller and all third party components (box, shields) is really limited.

Now, that said … I have to order one !

ODROID-U3

ODROID-U3

BlueTooth BLE on iOS and Mac OsX

The RfDuino arduino device i’m actually hacking is a bluetooth 4 (BLE) device. I was expecting to work with it as any bluetooth devices in a terminal session like with rfcomm in previous version of bluetooth.

In fact not ! BLE are not pairable as the classical BT device, they are discovered by the application itself. Then you have communication channel you can read or write to communicate.

Thanks to a post in a forum, I’ve found a really usefull tool lightblue allowing to connect any BLE device and send it data. This soft works on iOS and MacOsX.

You can also get Apple tool : Bluetooth explorer and Packet Logger here.