PIC TQFP-100 Breakout Board design overview
The PIC TQFP-100 Breakout Boards support PIC32s, PIC24s, and dsPIC33 devices that come in the TQFP-100 (0.4mm pitch) PT packages. They have all the support circuitry you'll need for the microcontroller, allowing you to concentrate on the rest of your project. It features:
- USB and external 3.3V regulated power-supply
- External only 5V regulated supply for USB Host projects
- Host enabled USB connector
- X MHz primary crystal
- 32.768 KHz secondary crystal for Real Time Clock projects
- One power, and two user programmable LEDs
- Reset button
- Programing ICSP header
- All the port pins broken out into two dual row headers
PIC or dsPIC in TQFP100 package
File:PICTQFP100 MCU 1.jpg The microcontroller is located on the top layer and in the center of the board, making it easier to solder those 100pins. Supporting circuitry is located on the bottom layer.
One power (PWR) and two user (P1 and P3) LEDs are available for development. Also provided is a reset tactile button (RESET).
MCU support circuitry
Support circuitry for the uC is on the bottom side of the board. A 3.3v,800mA voltage regulator (VREG1) is used to provide a stable power supply. The ferrite bead(L1) and 1uF capacitors (C9 and C16) provide noise suppression for the voltage regulator input. It's output is bypassed with a 1uF capacitor (C14).
The voltage regulator is powered either directly through the USB jack or through the DC-in jack.The rectifier diode (D2) prevents any current being sourced to the USB power line when both the external DC jack and the USB are connected. The ferrite bead(L1) and 1uF capacitors (C9 and C16) provide noise suppression for the voltage regulator input.
Power supply pins are decoupled with seven 0.1uF capacitors (C1-C7). The internal 2.5V voltage regulator is bypassed with a 10uF capacitor (C8).
A stable clock is provided by a XXMHz quartz crystal (X1) and two load capacitors (C10 and C1). Also provided is a secondary 32.768 KHz quartz crystal (X2) with it's load capacitors (C12 and C13) for any Real Time Clock operations.
The ICSP programing connection is brought to a header for easy development. The MCLR (RESET) programming pin is connected to the power supply through a 2K pull-up resistor (R1). This keeps the uC in reset until the power supply voltage reaches a safe operating level. Also added is a reset button (RESET), which grounds the MCLR pin, and causes the uC to reset.
By placing a jumper on HOST_EN you are connecting the 5V voltage regulator (VREG2) to the USB power line for host operation. A 1uF bypass capacitor (C14) is used on the 5V line.
Warning: Do not under any circumstances connect a host device (PC) while the HOST_EN has a jumper on it, there is a high probability you will damage the host. If you plan to use the board as an "USB device only", remove the HOST_EN jumper.
Broken out Pins
- PCB and placement notes
- soldering advise
Click for a full size placement image.
|IC1||1||PIC24/PIC32/dsPIC33||TQFP100 (pitch 0.4mm)"PT"|
|SJ1||1||ENVREG solder jumper||SJ_2|
- Operating modes
- extra software required
We used the Microchip USB stack to run the 18F2550 as a virtual serial port. Microchip's code is open but not redistributable. If you want to compile the source, download the stack from Microchip, then drag the source code into the install directory. See the detailed instructions in the PIC compiler how-to.
The virtual serial port (CDC) is an open standard, it should work on any modern operating system.
You don't need a driver, but you will need a .inf file to tell Windows how to use the device. A suitable .inf is included in the project archive.
Source and license
Taking it further
Here's some ideas for the future:
We'll post the most recent firmware updates on our blog. You can also join the discussion in the [forum].
You can [get one for $00], including worldwide shipping.
Your purchases at Seeed Studio keep the open source project coming, we sincerely appreciate your support!