Everyone is aware of that Raspberry Pi Pico growth boards are helpful for all the pieces from blinking some LEDs to powering a desktop robotic or a retro handheld gaming console. However the potentialities lengthen far past these widespread purposes. YouTuber 101 Issues not too long ago demonstrated an uncommon, however very fascinating, use case for these little boards—making walkie-talkies.
By following the steps taken by 101 Issues, a walkie-talkie or intercom system will be hacked collectively in a matter of minutes utilizing solely cheap and accessible {hardware}. The undertaking was designed round a Raspberry Pi Pico W, which is provided with built-in Wi-Fi. That wi-fi functionality permits two gadgets to speak instantly with out requiring a conventional radio module. As a substitute of transmitting audio over RF frequencies like traditional walkie-talkies, these gadgets convert voice into digital information and ship it throughout a Wi-Fi connection.
The circuit design could be very easy (📷: 101 Issues)
To seize sound, the construct makes use of a MAX4466 microphone module, a small and cheap board that outputs an analog sign appropriate with the Pico’s built-in Analog-to-Digital Converter (ADC). The sign is sampled and processed by the microcontroller earlier than being transmitted over the community.
On the playback aspect, the undertaking depends on a MAX98357A digital audio amplifier. This compact I2S Class-D amplifier can ship as much as 3 watts of energy right into a small speaker, making it greater than able to driving the construct’s tiny 30 mm speaker. As a result of the amplifier accepts digital audio by way of I2S, it pairs neatly with the Pico’s digital output capabilities.
As a substitute of including further buttons and LEDs for the consumer interface, the undertaking takes benefit of the Pico’s built-in {hardware}. The onboard BOOTSEL button doubles as a push-to-talk management, whereas the onboard LED supplies standing suggestions. Completely different blinking patterns point out connection levels equivalent to trying to find a associate system, establishing a Wi-Fi hyperlink, and being able to transmit.
A glance contained in the enclosure (📷: 101 Issues)
Communication between the 2 items makes use of a “faux peer-to-peer” networking methodology. When powered on, the gadgets robotically negotiate their roles. One turns into a Wi-Fi entry level whereas the opposite connects as a station. As soon as the pairing succeeds, these roles are saved in flash reminiscence so the gadgets can reconnect virtually immediately the following time they begin.
Audio transmission is dealt with via UDP packets to reduce latency. The system compresses audio samples from 12 bits down to eight bits utilizing A-law compression earlier than sending them throughout the community. On the receiving aspect, the audio is expanded again to 12 bits and handed to the amplifier for playback.
A 1 kΩ resistor positioned within the microphone’s energy line types a low-pass filter with the module’s onboard capacitors, serving to eradicate noise from the Pico’s Wi-Fi radio. In the meantime, a software program noise gate suppresses background hiss and prevents suggestions when neither system is actively transmitting. The {hardware} is housed in a 3D-printed enclosure and is powered by AA batteries.
When you’d prefer to construct your personal Pico-powered walkie-talkie, the construct directions and supply code have been made publicly accessible.