I’m back! I have a tendency to pause projects for lengthy periods of time, so here is part 2 of my Magic Sing Karaoke Microphone Tear Down. This time, we’re actually going to look inside the microphone, which serves as a remote control as well.
On the outside we see a nicely designed case with buttons, and an LCD screen.
Upon power up, the LCD reads “SYNC”. When you turn on the base station, they connect and the LCD says “Karaoke” which is the default menu option. The communications is two-way, what happens on the screen is reflected in the LCD. When you enter a song # or browse for a song and select it, the song # is displayed.
Let’s open it up! (Carefully)!
We see one lengthy PCB with a silver box on the end. That silver box indicates RF shielding…So that means the radio is under that hood.
Confirmed! These chips are a TI CC2400 transceiver (2.4ghz), an undocumented CASUH retaw1-05, and an SST 1Mbit flash chip. The retaw1-05 is a RF modem chip, but could not find a datasheet on it.
The back of the radio board is boring, but has a couple of connectors. Moving on…
How the two boards look when separated. At the left side of the long board is an ATMEGA48. It is right under the LCD so I’m going to guess it is the button/LCD controller. I’m pretty sure we can assume that the Atmel also connects to the retaw1-05 radio modem chip.
They made a failed attempt at covering that ATMega48..
Below we can see the codec chip (AIC311). This chip is responsible for converting the audio from the microphone into a digital stream. It has some other neat capabilities such as pitch changing, base, treble adjustments, etc. By the location, and the traces that run out to the right, I can extrapolate that this chip feeds directly into the bottom black connector going to the radio board. The Atmega48 surely has some control lines going to this as well.
It would be really neat if I could sniff the packets coming out of that CC2400. I’m also not sure if both the RF Modem and the CC2400 are generating radio frequencies. The datasheet (two page only) that I could find on the Retaw says it is 2.4ghz but it also says it can interface with a CC2400. There are many products from Korea that use this chip alone for both audio and data (phones, head phones, etc), so I’m a bit confused why they use both chips.