910 Supermic :: Quicker, easier and cheaper to make your own chip!

How it works

Supermic performes variable delay and sum beamforming on 8 mcirophones and outputs an I2S stream for easy processing. First the microphone data is passed in through 8 input pins in DDR(Double Data Rate) format. From there the chip converts the data to SDR (Single Data Rate); 1 wire per microphone. Individual microphone data is then passed through a third order CIC (Cascading Integrator Comb) Filter to convert it from PDM (Pulse Density Modulation) format to PCM (Pulse-code Modulation). Each microphone's data is then passed through a shift register that acts as a configurable delay and summed.This is then outputted by a I2S bus. Additionally, it passesthrough individual PCM output for ease of use.

How to test

1. Initial Setup

Connect Power Supply
- Ensure the module is correctly powered
Connect Clocks
- Connect a 3.072Mhz clock to bit_clk(uio_in[0])
- Connect a 48khz clock to lr_clk(uio_in[1])
- Ensure both clocks are aligned
Connect Microphones
- For each microphone, connect their VCC and GND pins to their respective sources
- Connect their clk pin to a 3.072Mhz clock
- Configure left/right pairs such what there are 4 of each type.
- For each left-right pair, combine their data wires (through a bread board for example) and connect them to ui_in[2:5]
Connect I2S reciever
- Connect an I2S reciever of your choice like a configured Raspberry Pi or supported speaker to the Beamformed PCM Output pin (uio[5])
Configure Delays
- Use pins uio[4:0] to confiure delays from the table below. A delay of 1 represents a delay of 1 sample at a sample rate of lr_clk
(Optional) Connect I2S recievers for passthrough
- Connect I2S recievers of your choice like a configured Raspberry Pi or supported speaker to the pins uo[0:7]

Monitor Output

Procedure
- Enable I2S reciever
- Enable Clock Signals
- Record data from I2S reciever (Varies based on chosen reciever)

External hardware

You need 8 digital microphones, a clock generator (can be a raspberry pi, microcontroller, etc.), and something that recieves the I2S output (this can be a rapberry pi or most audio output devices).

Delay Configuration

`delay_select`	mic_delays[0]	mic_delays[1]	mic_delays[2]	mic_delays[3]	mic_delays[4]	mic_delays[5]	mic_delays[6]	mic_delays[7]
0	0	0	4	4	8	8	12	12
1	0	0	4	4	10	10	12	12
2	0	1	2	4	5	5	5	6
3	0	1	1	2	3	4	5	6
4	0	1	2	4	7	8	9	11
5	0	0	0	6	6	10	10	10
6	0	3	6	6	8	9	11	14
7	0	5	5	6	10	10	10	15
8	0	0	3	5	5	8	11	11
9	0	5	5	5	10	10	10	15
10	0	3	3	7	7	10	10	14
11	0	1	3	5	7	10	11	12
12	0	2	3	5	8	10	11	13
13	0	4	4	7	7	10	10	14
14	0	2	3	5	8	10	11	13
15	0	1	1	3	4	7	11	14
16	0	2	3	4	4	6	12	13
17	0	0	1	2	6	7	8	12
18	0	3	4	4	5	10	11	11
19	0	0	4	7	8	8	11	12
20	0	0	0	0	1	1	1	1
21	0	3	3	3	3	4	4	4
22	0	5	5	5	5	6	6	6
23	0	5	6	6	6	6	7	7
24	0	4	5	5	5	6	6	6
25	0	0	0	0	6	6	6	6
26	0	3	5	5	7	8	10	13
27	0	2	4	5	7	8	10	13
28	0	5	7	7	9	10	12	15
29	1	5	7	7	9	10	12	15
30	0	0	0	0	0	0	0	0
31	0	2	4	6	8	10	12	14

#	Input	Output	Bidirectional
0	Bit Clock (3.072 Mhz)	PCM Out Mic 0	Delay Select 0
1	LR Clock (48Khz)	PCM Out Mic 1	Delay Select 1
2	PDM Input Mics 0,1	PCM Out Mic 2	Delay Select 2
3	PDM Input Mics 2,3	PCM Out Mic 3	Delay Select 3
4	PDM Input Mics 4,5	PCM Out Mic 4	Delay Select 4
5	PDM Input Mics 6,7	PCM Out Mic 5	Beamformed PCM Output
6		PCM Out Mic 6	Mic Clock
7		PCM Out Mic 7

910 Supermic

910 : Supermic