BPI AD/DA extend module

Produce Overview

Overview

The DA/AD module is specifically designed for BananaPi. It communicated with BananaPi through I2C bus. There is a LED light on the board that you can adjust brightness through DA. The module supply 4 ADC channel through header on the left side of module and the thermistor interface. The user can choose according to actual demand and use them. The module is easy to use even you don’t need to write C code. Because the module support wiringPi so you can use shell script to control it.

The PCF8591 is a single-chip, single-supply low-power 8-bit CMOS data acquisition device with four analog inputs, one analog output and a serial I2C-bus interface. Three address pins A0, A1 and A2 are used for programming the hardware address, allowing the use of up to eight devices connected to the I2C-bus without additional hardware. Address, control and data to and from the device are transferred serially via the two-line bidirectional I2C-bus.

The functions of the device include analog input multiplexing, on-chip track and hold function, 8-bit analog-to-digital conversion and an 8-bit digital-to-analog conversion. The maximum conversion rate is given by the maximum speed of the I2C-bus.

Product Specification

Produce Features

• 1. Use PCF8591T chip
• 2. DA/AD in one module
• 3. 8bit high resolution DA/AD
• 4. Compatible with wiringPi
• 5. Supply thermistor and photoresistance

Port

• 1. Banana Pi connection port，also can use on raspberry pi.
• 2. 4 external analog channel
• 3. Electric level switch jumper
• 4. LED of DA choice jumper

Product Parameters

• 1. Working voltage: 2.5V-6.0V
• 2. 8-bit successive approximation A/D conversion
• 3. Multiplying DAC with one analog output
• 4. Analog voltage range from Vss to VDD
• 5. 4 analog inputs configurable as single ended or differential inputs
• 6. Max sampling rate given by I2C-bus speed
• 7. −40°C to +85°C operation

Typical Application

• 1. Supply monitoring
• 2. Reference setting
• 3. Analog control loop

Testbench

• 1. Set the DA jumper close
• 2. Power up the BananaPi and install Bananabian
• 3. Install the wiringPi
• 4. Input the command in Terminal: gpio -x pcf8591:120:0x48 awrite 120 127
• 5. If the LED have the half brightness the module is OK

Just insert the module to Banana Pi, like the below picture:

D/A conversion sequence：**

A/D conversion sequence：**

Schematic diagram

How to use

How to use AD/DA module on BPI-M3


Step 1: Download WiringPI

$ git clone https://github.com/BPI-SINOVOIP/BPI-WiringPi.git111 -b BPI_M3
$ cd BPI-WiringPi
$ chmod +x ./build
$ sudo ./build

Step 2:Check the BPI I2C GPIO extend(PCF8591T) device to see if it's on track.(address 0x48)

(I2c port number for M3: 2 )

sudo su
i2cdetect -y 2
. 0 1 2 3 4 5 6 7 8 9 a b c d e f
00: -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- 48 -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --``` 

Step 3:Run the command and see if the LED on the board is working.

low brightness

gpio -x pcf8591:120:0x48 awrite 120 127

hight brightness

gpio -x pcf8591:120:0x48 awrite 120 12

Reference

video demo on youtube:

https://www.youtube.com/watch?v=ltTVOmmqmaE&feature=youtu.be

http://www.nxp.com/products/interface_and_connectivity/i2c/i2c_dacs_and_adcs/PCF8591T.html