cheapo - Allo.com

CHEAPO
Technical Manual
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CHEAPO
Figure 1: Sparky SBC + Cheapo
CHEAPO Features:
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192 kHz high-quality DAC out from Sparky board for best sound quality
138mW Direct Path™ Stereo Headphone Amplifier TPA6133A2
Available with different output connectors: RCA, 3.5mm phone jack, Optical
TOSLINK transmitter (S/PDIF)
Stereo DAC out SNR is >98dB and THD is <-80dB
Stereo Headphone Output Power is 138mW
Stereo Headphone Half Power THD + N @ 1 kHz (%) (KHz) is 0.008
Stereo Headphone SNR is 93dB
Stereo Headphone PSRR is 109dB
Sampling Frequency ranges from 8 kHz to 192 kHz
Small X2SON Package Ultra-low-noise voltage regulator for optimal audio
performance
Integrated EEPROM for automatic configuration (with write-protection)
Operating Temperature Range is -25C to 85C
The Cheapo board size: LWH = 68.7mm * 67.1mm * 23.1mm
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Cheapo is an Analog & S/PDIF Audio
Interface Shield to Sparky SBC
The Cheapo takes the analog audio signal (L&R) from the Sparky built in DAC through
the 3 pin on board header, delivers variable output analog audio to the Cheapo RCA
connectors. The Cheapo also, via the Texas Instruments TPA6133A2 headphone amp,
supports the direct use of headphones via the Cheapo’s 3.5mm audio jack. I2S
supports sample rate 192k/96k/48k/32k/24k/16k/12k/8k/88.2k/176.4k/44.1k/22.05k
/11.025k.
The Cheapo takes S/PDIF Digital audio signal out from the Sparky SBC through the 40
pin header and out through TOSLINK connector. S/PDIF supports sample rates of
96k/48k/44.1k/32k, biphase format stereo audio data output. S/PDIF is used to
transmit digital signals of a number of formats, the most common being the 48 kHz
sample rate format used in DAT and the 44.1 kHz format used in CD audio.
Component selection, Digital-Analog Partition and track layout have been in the
forefront of our design to ensure noise immunity and best possible audio playback
with the Cheapo.
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Top Side of Cheapo
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Bottom Side of Cheapo
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CHEAPO Header PIN-Out Details
CHEAPO - 40 Pin Bottom Connector
Sparky signal
PIN
PIN
3V3
1
2
DCIN +5V
I2C -2 SDA
3
4
DCIN +5V
I2C -2 SCLK
5
6
GND
GPIOB14
7
8
UART5_TX
GND
9
10
UART5_RX
GPIOB15
11
12
I2S_BCLK0
GPIOB16
13
14
GND
MUTE_AMP
15
16
SDZ_AMP
3V3
17
18
GPIOB30
I2C-3 SDA/SPI0_MOSI
19
20
GND
SPI0_MISO
21
22
GPIOB12
I2C -3 SCLK/SPIO_CLK
23
24
SPIO_SS
GND
25
26
S/PDIF
I2C-1 SDA
27
28
I2C -1 SCLK
I2S_MCLK0_2
29
30
GND
GPIOB18
31
32
GPIOB4
33
34
GND
I2S_LRCLK0_2
35
36
GPIOB13
GPIOB19
37
38
I2S_DIN_2
GND
39
40
I2S_DOUT_2
CHEAPO - J24 Header
Sparky signal
(3 PIN Header - Bottom)
SIGNAL
PIN
AUDIO LEFT
1
GND
2
AUDIO RIGHT
3
SD_HEAD
(GPIOB3)
** Highlighted signals are used by cheapo board
CHEAPO - J19 PIN OUT Details
RPI
SPARKY
PIN
PIN
SPARKY
RPI
5V
5V
1
2
5V
5V
NC
NC
3
4
NC
NC
SDA1-I2C
TWI2_SDA
5
6
GPIOB14
GPIO4
SCL1-I2C
TWI2_SCK
7
8
GPIOB15
GPIO17
NC
NC
9
10
GPIOB16
GPIO27
NC
NC
11
12
GPIOB30
GPIO24
GPIO23
SDZ_AMP
13
14
MUTE_AMP
GPIO22
GND
GND
15
16
GND
GND
CHEAPO - J20 PIN OUT Details
SIGNAL
PIN
PIN
SIGNAL
GND
1
2
GND
AUDIO RIGHT
3
4
AUDIO LEFT
AUDIO RIGHT
5
6
AUDIO LEFT
GND
7
8
GND
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CHEAPO Block Diagram
LED STATUS:
Green LED’S - Indicates Power up and SD (headset shut down) status - always glow
POWER (5V):
No need to connect extra power source to CHEAPO board, 5V power will source from
SBC through 40 pin header
SWITCHES:
HAT: switch SW1 position 1 is NC
Position 2 change to
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ON position for HAT eeprom write protect disabling
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OFF for enable (default state)
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