• Standard Raspberry Pi 40PIN GPIO extension header, supports Raspberry Pi series boards
• Onboard ADS1255, 2ch 24bit high-precision ADC, 30ksps sampling rate ±10 V
• Onboard DAC8552, 2ch 16bit high-precision DAC ±10 V
• Onboard input interface, for connecting I2C based sensor, like the STS30 temperature sensor
• Onboard input/output interface via BNC terminals, for connecting analog/digital signal

The trick is the shifting of the analog range of ±10 V to the adc range of 0 ... 5 V. To achieve that, we used the Bipolar Voltage to Unipolar Voltage ADC Driver circuit. And in order to shift it back from 0 ... 5 V to ±10 V, we used the Unipolar voltage output DAC to bipolar voltage circuit. Those two nifty calculators reduced the challenge to finding suiteable resistor values. The circuit is further equipped with a REF02 (+5 V ±0.2 % max. Precision Voltage Reference) and in order to reach voltages as high as 10 V, we use a NTA0515MC (DC-DC Converter ±15 V DC, ±33 mA Output). The unpopulated connector (K5) is an I2C / power interface to e.g. an STS-30 temperature sensor.

DEVICES	REMARKS
Raspberry Pi 4 model B, 4GB	30475.1
Power supply unit 5.1 V, 3 A	30475.2
Memory card microSDXC 64GB+SD 200MB/s	30475.3
Raspberry Pi OS Lite (64 Bit, no Desktop)	-
Raspberry Pi Imager	link
ADC+DAC hat	:-)

PIN FUNCTION	BCM	WIRING PI	DESCRIPTION
DRDY	P17	P0	ADS1255 data output，active-low
RESET	P18	P1	ADS1255 reset input
PDWN	P27	P2	ADS1255 Sync/Shutdown power input, active-low
CS0	P22	P3	ADS1255 chip select, active-low
C1	P23	P4	DAC8532 chip select, active-low
DIN	P10	P12	SPI data input
DOUT	P9	P13	SPI data output
SCK	P11	P14	SPI clock signal

The setup is identical to the (original) version of Waveshare. We made that hat pin-compatible.

You only need to keep in mind, that the scaling factors are different. For the input, this means that ±10 V is mapped to 0x000000 ... 0xFFFFFF (inverted) and the output 0xFFFF ... 0x0000 is mapped to ±10 V (non-inverted).

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