Embedded Eye

Give your gizmo the gift of sight

This tutorial introduces the ArduEye Aphid hardware. Firmware and software examples will be provided in another section.

PICTURES AND PINOUTS

The figure above shows the processor side and the camera side of the Aphid. These correspond respectively to the top and bottom sides of the PCB layout. Most important to users will be the Serial 0.1" header, located at the top as shown in the picture, and the peripheral 0.1" header, located towards the bottom. Some users may also use the JST TWI header and the 0.05" TWI header.

The next picture above shows the layout of the processor side of the PCB, and describes the pinout of the headers in detail.

The Serial header is used to plug the Aphid into a Sparkfun FTDI 5V breakout board, in the exact same manner as an Arduino Pro or Arduino Pro Mini. The signals are shown above.

The Peripheral header includes connections for power (VIN and GND), TWI/I2C clock and data lines (SDA and SCL), and direct connections to Arduino-defined ports D2 and D9. This header allows the sensor to be operated as an I2C slave sensor, or even an I2C master device if you prefer (and modify the code accordingly). The D2 and D9 are peripheral lines that can be repurposed for a variety of uses, for example to operate a laser module or to perform sophisticated hand-shaking for communications.

The JST TWI header provides access to just the four lines need to turn the sensor into an I2C slave sensor. You will need a four-lead cable terminated with a JST DF13 header to use this connector.

The 0.05" TWI header provides access to the same four lines for I2C, but with a smaller pitch to allow you to directly solder in an appropriate cable.

Finally, the above picture shows how to connect a Sparkfun 5V FTDI breakout board to the Aphid. Two simple rules are shown to help you remember which way to plug the sensor in. Personally, I prefer to remember that the side of the Aphid that has the processor and all the SMT mounted components corresponds to the side of the FTDI breakout board that also has SMT mounted components. In other words, just remember "SMT to SMT". You can also line up the "G" label on the Aphid to the GND label on the FTDI breakout board.

POWERING THE CHIP

The Aphid has an on-board voltage regulator that takes in 5V at VIN and regulates it down to 4.7V. This allows the Aphid to be operated from a USB port with resistance to power line fluctuations. The linear regulator does have reverse protection, and we have (unwittingly) verified this works, but of course you should avoid plugging the board in backwards if you can. The voltage regulator is a Linear Technology LT1761es5-byp and is rated to a maximum of 20v input, but we have not tested this full range. Note that if you provide more than 5V to the VIN, you should still never provide more than 5V to any of the other ports since these go directly to the ATmega328 and you could fry it.

COMPARISONS BETWEEN THE APHID AND THE ARDUEYE ROCKET SHIELD

The ArduEye Aphid is almost identical to the combination of an Arduino (UNO or Pro or similar), an ArduEye Rocket Shield, and a Stonyman breakout board, when the Stonyman breakout board is connected to the "fast" port 0 port and when an ADC is soldered into U1 of the Rocket Shield. The same pins D4 though D8 are used to send data from the processor to the Stonyman chip. The same SPI pins are used to operate the ADC. The only difference is that port A0 no longer needs to be used to connect or disconnect the Stonyman chip. On the Aphid the Stonyman chip is always connected. 

Note that for the Aphid chip, we disconnected the Stonyman's output from the processor. Thus it is no longer possible to use the processor's on-board ADC to acquire data. We don't think you'll mind- the external ADC on the Aphid acquires at 12 bits at 100ksps, which is much better than the 10 bits and 10ksps available with the on-board ADC.

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