ADC Relay Adapter USB V 8.0 for Raspberry PI

Transcription

1 ADC Relay Adapter USB V 8.0 for Raspberry PI INDUSTRIAL BERRY May 203

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3 Contents License 2 Introduction 3 3 Hardware implementation 5 4 Software implementation 4.0. An example with the ADC An example with the Relays Components list 5 Bibliography 7 i

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5 List of Figures 2. ADC Relay Adapter V Schematic MCU USB Schematic Relay Channel of ULN2003AD Schematic ADC Analog Board Layout iii

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7 List of Tables 5. ADC Relay Adapter USB V 8.0 for Raspberry PI v

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9 Chapter License Open-source hardware shares much of the principles and approach of free and open-source software. In particular, we believe that people should be able to study our hardware to understand how it works, make changes to it, and share those changes. To facilitate this, we release all of the original design files (Eagle CAD) for the IndustrialBerry hardware. These files are licensed under a Creative Commons Attribution Share-Alike license, which allows for both personal and commercial derivative works, as long as they credit Industrial- Berry and release their designs under the same license. The IndustrialBerry software/firmware is also open-source.

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11 Chapter 2 Introduction The ADC Relay Adapter V 8.0 (see Fig. 2.) is an extension board for Rasp- Berry Pi based on Open Hardware Design. It has two principal hardware features: control of 4 relays and 4 ADC channels. The board is connected to the Raspberry with an USB Bus, this feature allow the compatibility with other linux boards. 3

12 Chapter 2 Introduction Figure 2.: ADC Relay Adapter V 8.0 4

13 Chapter 3 Hardware implementation The USB interface is implemented with a classical FT232RL [] IC produced by FTDI. This IC is simple to use for the USB UART conversion. The IC3 a low cost PIC6F829 [2], this MCU controls the 4 relays and manages the 4 ADC channels. We can see the follows pins connection: RC4 sends data to the Linux Board RC5 receives data from the Linux Board RC3 controls Relay RC6 controls Relay 2 RC7 controls Relay 3 RB7 controls Relay 4 RA2 reads the ADC 0-0V RC0 reads the ADC2 0-0V RC2 reads the ADC3 4-20mA RB4 reads the ADC4 4-20mA We can see in figure 3.2 the part of the schematic with relays. Each device has a led for the status indication: Led Off -> Common Pin (C) connected with Normally Closed Pin (NC), Led On -> Common Pin (C) connected with Normally Open Pin (NO). The IC2 is the buffer ULN2003AD, this device can buffer 7 relays. Every channel contains two transistor in darlington configuration and diodes, see Fig.3.3. The first two ADC channels can read input from 0 to 0 V, therefore they have to use a voltage divider with a ratio of about 5. This circuit is implemented with two resistors of 2kΩ and 8kΩ. The last two ADC channels can read input from 4 to 20 ma, this circuit is implemented with a resistor of 00Ω. With the maximum current of 20 ma the ADC reads a voltage value of about 2 V. 5

14 Chapter 3 Hardware implementation USB to Serial VBUS 220nF C3 0uF 0R R6 0R 00nF FT232RL 0nF IC3 PIC6F829 +3V3 00k SV 0uF C7 REL G5LE CON5 2 REL3 G5LE R4 C IC VCC VCCIO RESET OSCI OSCO 3V3OUT USBDP USBDM TXD RXD 5 RTS 3 CTS DTR 2 DSR 9 DCD 0 RI 6 CBUS0 CBUS CBUS2 CBUS3 CBUS4 TEST JP 2 3 D+ D- VBUS C8 VDD RA5 AN3/RA4 MCLR/VPP RX/RC5 TX/RC4 VSS RA0/AN0/ICSPDAT RA/AN/VREF+/ICSPCLK RA2/AN2/INT RC0/AN4 R9 C9 RC/AN5/SDA AN7/RC3 RC2/AN6 RC6 RC7 RB4/AN0 RB5 RB7 RB6/SCL O REL O REL3 VBUS USB-RESET D+ D- RX_PIC TX_PIC CTS_PIC RTS_PIC MCLR VBUS ICSPDAT ICSPCLK D+ D- VBUS VBUS LED LED2 MCLR RX_PIC TX_PIC REL REL2 REL3 REL4 VBUS VBUS P ICSPDAT ICSPCLK ADC ADC2 SDA ADC3 ADC4 SCL P USB 6 A Figure 3.: Schematic MCU USB B C

15 P CON7 2 3 CON8 2 3 S O S O REL4 REL3 P USB to Serial VBUS VBUS USB ADC www R6 0R R4 0R REL3 G5LE 2 CON5 2 K3 3 REL REL G5LE P S O 2 REL3 220R LED3 R2 VBUS VBUS REL 220R LED R0 R7 0R R5 0R REL4 G5LE CON6 2 3 K4 REL2 REL2 G5LE 2 P S O 2 K IC2 REL I O 6 K REL2 2 I2 O2 5 K2 REL3 3 I3 O3 4 K3 REL4 4 I4 O4 3 K4 5 I5 O5 2 6 I6 O6 7 I7 O7 0 8 CD+ 9 VBUS ULN2003AD K2 Figure 3.2: Schematic Relay REL2 REL4 220R LED2 220R LED4 R R3 4/04/203 5:07:3 D:\Raspberry_hardware\USB-ADC\USB-ADC V 8.0\USB-ADC.sch (Sheet: /) 7

16 Chapter 3 Hardware implementation Figure 3.3: Channel of ULN2003AD A TERMINAL-2-PCB 2 TERMINAL-2-PCB 2 ADC 00pF C2 R R2 2k 8k CON ADC2 00pF C4 R5 R6 2k 8k CON2 TERMINAL-2-PCB 0R R3 2 TERMINAL-2-PCB 0R R4 2 B ADC3 00pF CON3 ADC4 00pF CON4 C5 R7 00R C6 R8 00R Figure 3.4: Schematic ADC Analog C 8

17 C 5 C3 SV R4 C7 REL CON5 IC R9 X IC3 JP R0 R R2 CON6 R5 IN IN2 IN3 IN4 C2 ADC CH 0-0 V C4 CON R5 R6 ADC CH2 0-0 V CON7 R6 CON2 R7 ADC CH ma CON3 R8 ADC CH ma CON4 ADC Relay Adapter V 8.0 USB for Raspberry PI LED LED2 LED3 LED4 R3 REL2 R IC2 C8 REL3 R3 R2 C5 R4 C6 C9 CON8 R7 REL4 NO C NC NO C NC NO C NC NO C NC Figure 3.5: Board Layout SB-ADC\USB-ADC V 8.0\USB-ADC.brd 9

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19 Chapter 4 Software implementation The Raspberry Pi sees our board as a /dev/ttyusb0. It is possible to control the board with a serial protocol from shell or a compiled program. This is the frame protocol: SOP ( byte) Start of frame char 0x49 CMD ( byte) Command LEN ( byte) Data length DATA (n byte) Data FCS ( byte) Xor of all previous bytes Possible commands: SET R EL C MD = 0x02 GET A DC C MD = 0x03 GET R EL C MD = 0x04 ADC S T AT E = 0x05 REL S T AT E = 0x06 The ADC Board produces an ACK = 0x00 for every correct message An example with the ADC Get data from ADC: We send this frame on ttyusb0 -> SOP = 0x49 GET A DC C MD = 0x03 LEN = 0x00 F CS

20 Chapter 4 Software implementation We receive from the board -> The ACK message SOP = 0x49 ACK = 0x00 LEN = 0x00 FCS The ADC State SOP = 0x49 ADC S T AT E = 0x05 LEN = 0x08 DATA = LO U INT 6(adc) DATA = HI U INT 6(adc) DATA = LO U INT 6(adc2) DATA = HI U INT 6(adc2) DATA = LO U INT 6(adc3) DATA = HI U INT 6(adc3) DATA = LO U INT 6(adc4) DATA = HI U INT 6(adc4) FCS An example with the Relays Set the Relays: We send this frame on ttyusb0 -> SOP = 0x49 SET R EL C MD = 0x02 LEN = 0x02 REL3 4 = 0x?? REL 2 = 0x?? FCS We receive from the board -> The ACK message SOP = 0x49 ACK = 0x00 LEN = 0x00 FCS The Relays State 2

21 SOP = 0x49 REL S T AT E = 0x06 LEN = 0x04 DAT A = Status R elay DAT A = Status R elay 2 DAT A = Status R elay 3 DAT A = Status R elay 4 FCS 3

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23 Chapter 5 Components list In the table 5. we can see the Bill of Material for the board, all the components are available on-line. For simplicity, every component has a DigiKey order code ( 5

24 Chapter 5 Components list Quantity Value Package Parts Digikey-cod Unit Price $ 4 Yellow 206 LED, LED2, LED3, LED ND Ω 0603 R3, R4, R4, R5, R6, R7 P0.0GCT-ND Ω 0603 R7, R8 RMCF0603FT00RCT-ND Ω 0603 R0, R, R2, R3 RMCF0603JT220RCT-ND kω 0603 R, R5 RMCF0603FT2K00CT-ND kω 0603 R2, R6 P8.20KABCT-ND kω 0603 R9 RMCF0603JT00KCT-ND pf 0603 C2, C4, C5, C ND 0.0 0nf 0603 C ND nf 0603 C ND nf 0603 C ND uf 206 C3, C ND G5LE G5LE REL, REL2, REL3, REL4 G5LE--36DC5-ND.45 FT232RL SSOP-28 IC ND 4.50 ULN2003AD SSOP20 IC ND 0.45 PIC6F829 SSOP20 IC3 PIC6F829-I/SS-ND.86 USBSMD USBSMD X WM76CT-ND.59 4 TERMINAL-2-PCB 2 X 5.08mm CON, CON2, CON3, CON4 ED2609-ND TERMINAL-3-PCB 3 X 5.08mm CON5, CON6, CON7, CON8 ED260-ND 0.45 PCB 4.00 Total Table 5.: ADC Relay Adapter USB V 8.0 for Raspberry PI 6

25 Bibliography [] Future Technology Devices International Ltd. FT232R USB UART IC Datasheet. [2] Microchip. PIC6F829 Datasheet. 7