TAILIEUCHUNG - Practical Arduino Cool Projects for Open Source Hardware- P34

Practical Arduino Cool Projects for Open Source Hardware- P34: A schematic or circuit diagram is a diagram that describes the interconnections in an electrical or electronic device. In the projects presented in Practical Arduino, we’ve taken the approach of providing both a photograph and/or line drawing of the completed device along with a schematic. While learning to read schematics takes a modest investment of your time, it will prove useful time and time again as you develop your projects. With that in mind, we present a quick how-to in this section | CHAPTER 15 VEHICLE TELEMETRY PLATFORM Other interesting items in your USB OBD-II adapter are the LM317 and 7805 voltage regulators and the FTDI chip that provides the USB interface see Figure 15-7 . Figure 15-7. Inside a typical USB OBD-II adapter The ELM327 provides a serial nterface on pins 15 through 18 at 5V so all the USB OBD-II adapter does is connect the FTDI chip in front of that interface to convert it to USB. We don t want to use USB though so what we ll do is bypass the FTDI chip and talk directly to the communications port on the ELM327. In the USB OBD-II adapter we used in our prototype the ELM327 is based on a PIC18F2480 in a 28-pin SOIC package with serial connections on the following pins pin 15 RTS Ready To Send active low pin 16 Busy pin 17 RS232Tx TTL level 0-5V not full RS-232 voltage pin 18 RS232Rx TTL level 0-5V not full RS-232 voltage pin 8 and 19 Ground In the photo shown in Figure 15-7 the chip is oriented with pin 1 in the bottom left corner near a tiny dimple and the rest are numbered counterclockwise from there. This puts pin 15 on the top right corner nearest the silver 4Mhz crystal pin 16 just left of that and so on. Different ELM327 adapters use different casing styles so you may need to improvise if your adapter is different than ours. Remove the PCB from the plastic case by gently prying up the edges of the board so that it pops off the four plastic legs that double as screw mounts for the top of the case. In one of the adapters we used for our prototypes the PCB came out easily but in the other one the plastic legs had been cracked and expanded by the screws holding the case together and the PCB was jammed in tight. We had to use wire cutters to clip each leg off flush with the top of the PCB before we could get it out. If you have to do this be very careful not to damage any of the nearby surface-mount components. 309 CHAPTER 15 VEHICLE TELEMETRY PLATFORM Next start slimming down the circuit board by unplugging the ribbon cable .

• Phần cứng
• sửa chữa máy tính
• sổ tay phần cứng
• MainBoard
• thiết bị máy tính
• thiết bị mạng
• lắp ráp máy tính
• Phần cứng máy tính
• lỗi máy tính
• hệ thống mạch máy tính
• điện máy tính
• Tài liệu máy tính