Arduino Pro Mini
I needed an 2 channel Analog/Digital converter with 10 bit resolution and I2C bus, with minimal cost and effort. To my surprise it looks like, that an Arduino Pro Mini module from China just made it for 2.50 EUR, including shipping, see http://ebay.com (search for: PRO MINI ATMEGA328 5V/16M).
If you buy via http://ebay.de take care about the original Arduino layout with the right boot loader installed.
- Dimensions: 18 x 33 mm
The version from gc_supermarket has a layout change, which is of benefit, because you have now an ISP (In System Programming) connector at the left side (6 pins), see the pictures (click on the picture to enlarge). Fortunately the pinout to the Serial-USB converter is the same.
The original version looks like:
AVR ISP programmer
A very cheap ISP programmer can be bought AVR-USB-Stick for 10 EUR inclusive shipping (kit). The tutorial is here. More details can be found at Mikrocontroller. The original development was done at LadyAda (Software).
USB to Serial Converter
When you search on http://ebay.de for the title "CP2102 Module Modul USB to TTL Converter Konverter" (no. 280736990675 , seller: ether.deal) you will find a module which also has the important signal DTR brought out to a solder point (green wire). Here you have to solder a pin, to connect to the Arduino Pro Mini module. Price about 4.30 EUR inclusive shipping.
The program was developed with Arduino IDE Version 1.0.5, with the wire library.
Usually an Arduino module will come with the boot loader preinstalled. In this case it was not the right boot loader. The green LED switches ON, when you power up the module, but the connection to the PC with an USB/Serial converter will fail. So, I had to solder the 6 pins for the ISP programming and flashed the proper Arduino boot loader with an ISP programmer.
Select from the Arduino IDE menu Tools the programmer "USBtinyISP", the board "Arduino Mini or Pro Mini (5V, 16 MHz)w/ ATmega328". Then click on Install Bootloader. Even when the module is powered with 3.3V only, the 16 MHz clock works stable.
Next step is to connect a USB/Serial converter with the pins:
Arduino USB/Serial signal color signal note GND brown GND RXD red RXD to Arduino TXD orange TXD from Arduino +5V yellow +5V DTR green DTR for Reset pulse
The trick with the programming via USB is, that via DTR pulse a Reset signal will start the boot loader. If within a few seconds the programmer (avrdude) responds, the flash ROM programming will start.
For an easier Arduino programming start read Getting started.
The analog value will be averaged with 8 samples, in order to reduce the noise.
For help with the C programming look at the Language Reference.
If you want to get the hex file of the compiled program, select in Arduino/Preferences verbose output at compile time. Then you can see in the output window the file path of the hex file, and copy it to an other place. Because this path will be deleted, when you quit the Arduino IDE.
A/D Converter Hardware
For the schematic have a look at RaspberryPiWobbulator#A.2FD_converter.2C_hardware_Nano3.
Low power operation
Normally the Arduino Pro Mini draws about 10 mA, when using the RAW supply input.
For low power operation please see at Link #4.
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-- RudolfReuter 2013-12-19 12:47:23