Matrix - Analog to Digital Converter
Contents
Introduction
- The Matrix-Analog_to_Digital_Converter is a single-chip, single-supply low-power 8-bit CMOS data acquisition device.
- It utilizes the PCF8591 chip 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 maximum conversion rate is given by the maximum speed of the I2C-bus.
- The I2C hardware address is configured to 1001000x
- The operating supply voltage is from 2.5V to 6.0V，Among the 2.54 mm spacing pin header the 5V pin is the supply voltage. If you need 0 - 3.3V analog signals and keep the acquisition resolution you can connect it to a 3.3V supply voltage.
Features
- Wide range supply voltage: 2.5V - 6.0V
- I2C interface: 3.3V/5V
- 8-bit A/D x 4
- 8-bit D/A x 1
- Small and easy to be used in various situations
- 2.54 mm spacing pin
- PCB dimension (mm): 16 x 24
- Pin Description:
| Pin | Description |
| SDA | I2C SDA |
| SCL | I2C SCL |
| 5V | Supply Voltage 5V |
| GND | Ground |
| AOUT | Analog Output |
| A3 | Analog Input3 |
| A2 | Analog Input2 |
| A1 | Analog Input1 |
| A0 | Analog Input0 |
Basic Device Operation
The PCF8591's I2C-bus is for bidirectional, two-line communication between different ICs or modules. The two lines are a Serial DAta line (SDA) and a Serial CLock line (SCL). Both lines must
be connected to a positive supply via a pull-up resistor. Data transfer may be initiated only when the bus is not busy. The AINT0 - AINT4 pins are analog inputs which can be configured to single-ended or differential inputs. The supply voltage is 0 - VDD.
1. Each PCF8591 device in an I2C-bus system is activated by sending a valid address to the device. The address consists of a fixed part and a programmable part. The programmable part must be set according to the address pins A0, A1 and A2. The address is always sent as the first byte after the start condition in the I2C-bus protocol. The last bit of the address byte is the read/write-bit which sets the direction of the following data transfer.
2. The second byte sent to a PCF8591 device is stored in its control register and is required to control the device function. The upper nibble of the control register is used for enabling the analog output, and for programming the analog inputs as single-ended or differential inputs. The lower nibble selects one of the analog input channels defined by the upper nibble.
3. The on-chip D/A converter and a high-gain comparator are used temporarily during an A/D conversion cycle. An A/D conversion cycle is always started after sending a valid read mode address to a PCF8591 device. The A/D conversion cycle is triggered at the trailing edge of the acknowledge clock pulse and is executed while transmitting the result of the previous conversion。
Download Matrix Source Code
All the matrix modules' code samples are open source. They are maintained on GitHub - https://github.com/friendlyarm/matrix.git
Each branch in this hub contains the matrix modules' code samples for a board that the matrix modules can work with.
- The nanopi branch contains the matrix modules' code samples for the NanoPi
- The tiny4412 branch contains the matrix modules' code samples for the Tiny4412
- The raspberrypi branch contains the matrix modules' code samples for the RaspberryPi
Please follow the steps below to get the source code:
Install the git utility on a PC running Ubuntu14.04
$ sudo apt-get install gitClone the matrix code from GitHub
$ git clone https://github.com/friendlyarm/matrix.gitIf this is successful a "matrix" directory will be generated, which will contain all the matrix modules' code samples.
Connect to NanoPi
Preparations
Please install a Debian on a NanoPi and an appropriate cross compiler on a PC. Please refer to wiki:NanoPi
Compile a NanoPi kernel. Note: please use the kernel's source code from the nanopi-v4.1.y-matrix branch.
$ git clone https://github.com/friendlyarm/linux-4.x.y.git
$ cd linux-4.x.y
$ git checkout nanopi-v4.1.y-matrix
$ make nanopi_defconfig
$ touch .scmversion
$ makeHardware Connection
Please refer to the following connection diagram to connect the Matrix-Analog_to_Digital_Converter to the NanoPi
Connection Details:
| Matrix-Analog_to_Digital_Converter | NanoPi |
| SDA | Pin3 |
| SCL | Pin5 |
| 5V | Pin4 |
| GND | Pin6 |
Compile Test Program
Please login the matrix hub and enter the nanopi branch
$ cd matrix
$ git checkout nanopiCompile the matrix code
$ make CROSS_COMPILE=arm-linux- clean
$ make CROSS_COMPILE=arm-linux-
$ make CROSS_COMPILE=arm-linux- installNote: please make sure to install the cross compiler "arm-linux-gcc-4.4.3" on your PC, which is used to compile files for the NanoPi-Debian.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-Analog_to_Digital_Converter" module is "matrix-adc".
Run Test Program
Please copy the library files and test program to the NanoPi
$ cp install/usr/bin/* nanopi_rootfs/usr/bin/
$ cp install/lib/* nanopi_rootfs/lib/ -dPower on the NanoPi and run the following command in Debian's terminal
Note: this module is not plug and play therefore before running the module please make sure it is connected to a NanoPi.
$ matrix-adcCode Sample
int main(int argc, char ** argv)
{
int devFD;
int data, channel, mode;
if ((devFD = pcf8591Init()) == -1) {
printf("Fail to init pcf8591\n");
return -1;
}
if (pcf8591SetCtrl(devFD, PCF8591_INIT_AD_CONTROL) == -1) {
printf("Fail to Set pcf8591 control AD\n");
pcf8591DeInit(devFD);
return -1;
}
mode = 0;
printf("pcf8591 working as AD in mode%d\n",mode);
for (channel = PCF8591_AIN_CHANNEL0; channel <= PCF8591_AIN_CHANNEL3; channel++) {
data = pcf8591Read(devFD, mode, channel);
printf("Channel%d's value: %d\n",channel,data);
}
pcf8591DeInit(devFD);
return 0;
}Connect to Tiny4412
Preparations
Please refer to the Tiny4412's user's manual to install a UbuntuCore on the Tiny4412 and install an appropriate cross compiler on a PC.
Note: only the Tiny4412SDK-1506 carrier board can work with this module.
Hardware Connection
Please refer to the following diagram to connect the Matrix-Analog_to_Digital_Converter to the Tiny4412
Connection Details:
| Matrix-Analog_to_Digital_Converter | NanoPi |
| SDA | CON18 SDA |
| SCL | CON18 SCL |
| 5V | CON18 5V |
| GND | CON18 GND |
Compile Test Program
Please login the Matrix hub and enter the matrix-tiny4412 branch
$ cd matrix
$ git checkout tiny4412Compile the matrix code
$ make CROSS_COMPILE=arm-linux-gnueabihf- clean
$ make CROSS_COMPILE=arm-linux-gnueabihf-
$ make CROSS_COMPILE=arm-linux-gnueabihf- installNote: please make sure to install the cross compiler "arm-linux-gnueabihf-gcc-4.7.3" on your PC, which is used to compile files for the Tiny4412-UbuntuCore.
Generated library files are under the "install/lib" directory. Applications are under the "install/usr/bin" directory. The test program for the "Matrix-Analog_to_Digital_Converter" module is "matrix-adc".
Run Test Program
Please copy the library files and test program to the Tiny4412
$ cp install/usr/bin/* tiny4412_rootfs/usr/bin/
$ cp install/lib/* tiny4412_rootfs/lib/ -dPower on the Tiny4412 and run the following command in UbuntuCore's terminal
$ matrix-adcCode Sample
int main(int argc, char ** argv)
{
int devFD;
int data, channel, mode;
if ((devFD = pcf8591Init()) == -1) {
printf("Fail to init pcf8591\n");
return -1;
}
if (pcf8591SetCtrl(devFD, PCF8591_INIT_AD_CONTROL) == -1) {
printf("Fail to Set pcf8591 control AD\n");
pcf8591DeInit(devFD);
return -1;
}
mode = 0;
printf("pcf8591 working as AD in mode%d\n",mode);
for (channel = PCF8591_AIN_CHANNEL0; channel <= PCF8591_AIN_CHANNEL3; channel++) {
data = pcf8591Read(devFD, mode, channel);
printf("Channel%d's value: %d\n",channel,data);
}
pcf8591DeInit(devFD);
return 0;
}Connect to RaspberryPi
Connect to Arduino
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