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2011-11-24

nRFready Microphone

nRF6915/AKMS_MIC_2

User Guide v1.0

Summary of Contents for nRF6915/AKMS MIC 2

Page 1: ...All rights reserved Reproduction in whole or in part is prohibited without the prior written permission of the copyright holder 2011 11 24 nRFready Microphone nRF6915 AKMS_MIC_2 User Guide v1 0 ...

Page 2: ... of these products can reasonably be expected to result in personal injury Nordic Semiconductor ASA customers using or selling these products for use in such applications do so at their own risk and agree to fully indemnify Nordic Semiconductor ASA for any damages resulting from such improper use or sale Contact details For your nearest dealer please see http www nordicsemi com Receive available u...

Page 3: ...irmware content 6 2 3 Documentation 7 2 4 Finding content on the web 7 3 System overview 8 4 Kit operation 10 4 1 Pairing procedure 11 4 2 Programming boards 11 4 3 Compiling firmware 12 5 Hardware description 13 5 1 nRF2788 Microphone 13 5 2 nRF2789 Receiver 14 5 3 Layout guidelines 15 5 4 Power supply 15 5 5 Antenna 16 5 6 Crystal oscillator 16 5 7 User interface 16 5 8 Programming interface 17 ...

Page 4: ...receiver The Kit includes two microphone boards a receiver board with both analog and USB audio interface plus a complete set of design files source code and documentation The nRFready Microphone Reference Kit Design has the following key features Complete reference design for a dual 2 4 GHz RF microphone system Uncompressed 16 bit digital audio 32 kHz sampling rate Programmable latency from 20 to...

Page 5: ...et of typographic rules to make the document consistent and easy to read The following writing conventions are used Commands are written in Courier New Pin names are written in bold Courier New File names and User Interface components are written in bold Cross references are underlined and highlighted in blue ...

Page 6: ...ent 2 1 Hardware content The nRFready Microphone hardware consists of 2 microphone boards 1 receiver board 2 AAA battery holders 4 AAA batteries 1 USB cable 2 2 Firmware content The nRFready Microphone firmware consists of Microphone source code with pre compiled HEX files Receiver source code with pre compiled HEX file ...

Page 7: ... the files to a folder on your PC that you want to use for development To be able to compile the source code and program the boards three programs are required in addition to a PICkit 2TM or PICkit 3TM programmer All programs are verified to work on a PC running Windows 7 64 bit The programs must be downloaded from http www microchip com PICkit2TM Programmer v2 61 or PICkit3TM MPLAB IDE v8 76 HI T...

Page 8: ...ly will hold in his hand while singing or talking Receiver This is the audio output device that the user typically has connected to a computer to record or playback audio The system is designed to be simple to set up and use with only one button and LED on the microphone board and one button and two LEDs on the receiver board The buttons are used to power ON OFF or pair the boards while the LEDs i...

Page 9: ...kets acknowledgements synchronization audio buffers and link quality The receiver board has two nRF2460s that are placed on the same PCB and the nRF2460 has a built in synchronization mechanism that allows the two nRF2460s to operate in close proximity yet without interfering with each other In addition the two microphones use non overlapping hopping tables that are spread across the entire 2 4 GH...

Page 10: ...wo LEDs indicate that the receiver board is waiting for a microphone to link up After link up a solid light on either of the LEDs will indicate that a microphone is connected Similarly on the microphone board a blinking LED means that there is no link with a receiver yet while a solid LED means that the microphone has successfully linked with a receiver board See Table 2 for a description of LED s...

Page 11: ...ne board microcontrollers using a third party development tool The nRFready Microphone uses a PICkit 2TM Development Programmer for in circuit programming of the PIC16F684 microcontroller You can use either PICkit 2TM or the PICkit3TM The development tool must be bought separately since it is not included in this kit The boards can be programmed in one of two ways The pre compiled HEX files for th...

Page 12: ...ce files for both microphones referred to as the red microphone and the blue microphone This means you must make a small change to one of the source files to decide which microphone firmware shall be compiled The AdjustableParameters h defines whether the microphone project should be compiled for the red or the blue microphone define RED_MIC comment this to create hex file for BLUE_MIC Note that p...

Page 13: ...hone input For demonstration purposes a MP3 player can also be used The analog signal is sampled by a 16 bit AK5700 mono ADC with a microphone amplifier and Auto Level Control ALC The sampled signal is fed to the nRF2460 wireless mono audio streamer that transmits the signal to the receiver board The microphone board is powered from two AAA batteries See Figure 4 for details Figure 4 Block diagram...

Page 14: ... output the converted analog signal to two phono outputs and an AK5374 USB ADC for USB connection to a computer The board will enumerate as a two channel recording device when connected to a computer The receiver board is powered from a USB connection See Figure 6 Figure 6 Block diagram of receiver board RCA jack 2 Audio streamer nRF2460 Stereo DAC AK4430 Audio streamer nRF2460 Stereo DAC AK4430 U...

Page 15: ...upling guidelines in the various ICs product specifications before making any changes to the design 5 4 Power supply As in all electronic design the quality of the design is not only decided by the active devices themselves but also by how they work together Basically there are two very important things to look out for in an nRF2460 design Noise crosstalk through the power supply Ground layout The...

Page 16: ...df or gerber formats 5 5 Antenna The antenna type implemented on the microphone and receiver boards is a quarter wavelength monopole antenna printed on the PCB The antennas on the boards are tuned to be resonant at 2 44 GHz and the impedance of each antenna is matched to the 50Ω output of the nRF2460 device matching network with the use of a shunt capacitor to ground close to the antenna feed poin...

Page 17: ...10 Issue 8 RSS Gen Issue 3 The test reports are available for download from www nordicsemi com 6 Troubleshooting I have followed the Getting Started Guide but there is no audio What should I do Try to pair the boards again by following the procedure in section 4 1 on page 11 Try new AAA batteries Check the USB cable When I unplug the MP3 player from the microphone board or pause music a short nois...

Page 18: ...Mouser Electronics Authorized Distributor Click to View Pricing Inventory Delivery Lifecycle Information Nordic Semiconductor nRF6915 ...

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