Audio and I/O via SPI for Raspberry + PjSip/PjMedia
SLM-PJBERRY is an evaluation board compatible with Raspberry PI, PI-2 and PI-3, developed around a powerful mixed signal microcontroller which runs our firmware to perform a PjMedia audio codec and I/O controller. It is mainly thought for audio/video streaming in conjunction with open-source pjsip/pjmedia library to develop VOIP applications compliant with SIP standard. It completes Raspberry with:
- An audio input able to directly accept a conventional low-cost microphone signal. The analog audio signal coming from the microphone is sampled at 16Ksample/sec and a smart adaptive management is able to prevent buffer overrun/underrun events which could produce jitters due to little sample frequencies mismatching in the streaming chain.
- An audio output, able to directly drive an 8 ohm speaker load. This audio digital channel is also sampled at 16Ksample/sec and it is completely independent from the native stereo audio output of Raspberry, that can be used for other purposes.
- A smart rugged switching power supply, controlled by onboard microcontroller, able to accept an input voltage between 9V and 15V (5V version is available on request). Onboard microcontroller runs at a very low power, also during Raspberry power off, so Raspberry can be turned on at any time, by an external signal or RTCC output.
- An intelligent watchdog, managed by onboard microcontroller, able to safely reset Raspberry by taking power away from it and than feeding power again after a couple of seconds. In this way even memory leaks effects and other long term bugs that can lead Raspberry software to a dead end, are safely wept away.
- A RTCC (Real Time Clock Calendar) unit, avaliable upon request, directly connected to Raspberry I2C channel. Being wired to the microcontroller that controls Raspberry power supply, this unit is able to turn Raspberry on and off under the control of your program, to greatly reduce power consumption when Raspberry doesn't need to be operative, for example when is battery powered to do a periodical task once a day.
- A numerical keyboard interface that doesn't waste any Raspberry's GPIO.
- Two 200mA outputs, able to directly drive 12V relays, or to be used as 5V level shifter to drive till 3 numerical display (7 segments type) and 3 additional outputs, only by using very low price shift-registers (74HC4094).
- A 12V/500mA power output able to supply a low cost graphical colour display, connected to TV-OUT Raspberry connector (video composite signal output) only when a VOIP connection is established, thus avoiding waste of power and insuring a much longer life to LCD. Alternatively this output could be used to drive an additional relay
Although the image shows the module in combination with the old Raspberry PI, it works greath with PI-3, supporting fluid H264 video compression.
This Evaluation Board is produced by CTA-Microsystem that currently produces also an IP videodoorphone product-line which rely on a customization of our microcontroller firmware.
Besides customized microcontroller firmware, we can offer full development support of audio-video VOIP devices capable of remote controlling digital I/O and monitoring, like IP video-doorphones or remotely querying data-loggers capable of audio-video live communication or... well... it comes upon your fantasy!.
If you are interested in development of an IP device with VOIP capability, feel free to contact us using our contact-form.