2019-08-24

Building the Beeper+RTC+FM Radio Assembly

The piezo beeper, the real-time clock and the FM radio are assembled together onto a 1/2 sized perma-proto breadboard. These three components are all either controlled or used by the Raspberry Pi and so it makes sense to group them together into a single assembly.

The piezo beeper is connected to GPIO pins #37 (GPIO26) and #39 (GND). It is activated for a fraction of a second (chirped) by the Comvette software whenever a touch-screen input is received.

The Real-Time Clock (RTC) module receives power from GPIO pins #4 (+5V) and #6 (GND) and communicates with the Raspberry Pi via pins #3 (SDA1) and #5 (SCL1).

The FM Radio module also receives power from GPIO pins #4 (+5V) and #6 (GND) and also communicates with the Raspberry Pi via pins #3 (SDA1) and #5 (SCL1).

Communication between the Raspberry Pi and the RTC and FM Radio module is carried by the I2C bus (SDA1 & SCL1). Up to 127 devices may share the I2C bus.

You've probably been confused by the various ways the Raspberry Pi GPIO pins are referenced. Just remember that there are GPIO ports and there are GPIO pins. The Comvette software uses the GPIO port designations provided by Broadcom (the manufacturer of the Raspberry Pi chipset) but those designations are mapped to the physical GPIO header pins by the designers of the Raspberry Pi. So whenever a GPIO pin is referenced in the Comvette software you will need to refer to a GPIO pin diagram to see where the GPIO port actually appears in the GPIO header. The reason for this port-to-pin mapping is because Broadcom may change the the number of GPIO ports in the future and/or the Raspberry Pi designers might need to reorganize the physical layout of the GPIO pins in a future Raspberry Pi design. By consulting the GPIO diagram for your model of Raspberry Pi you will be able to be certain that you are making connections to the correct pins and ports.

For example, the piezo beeper is attached to GPIO26 which according to the GPIO pin diagram is physical pin #37. The beeper also uses a nearby GND on pin #39.

Raspberry Pi GPIO pin diagram:

NOTE: More information on Raspberry Pi GPIO can be found at the Raspberry Pi Foundation.