3.3V USB Powered3.3V Board Powered 5V USB Powered 5V Board Powered 1.8V and 2.5V Buffered Isolated Dual-Chip Setup
USB Powered 3.3V Configuration
NSDSP based on PIC16LF1454 must be used for all 3.3V configurations
When NSDSP is powered by USB, the EN pin (see pinout) must be tied to VDD to ensure NSDSP does not enter sleep mode while USB cable is attached. Since USB voltage is 5V, a regulator must be used to convert USB voltage to 3.3V. The regulator must produce enough power for NSDSP, the target device and any extra circuicity. The values of C1 and C2 capacitors depend on the regulator used. To comply with USB standard, total capacitance may not exceed 10µF.
For the locations of the NSDSP pins, refer to the pinout diagram. Only PIC pins used for connecting NSDSP are shown. For the list of connections necessary to run the PIC, refer to the datasheet for your PIC device.
This schematics does not show any ESD protection devices which may or may not be needed for the application.
To enable programming and debugging, MCLR, PGC, and PGD pins must be connected. Also USB ground, NSDSP ground and PIC ground must be connected together. R1 is necessary to prevent damages to PIC or NSDSP. R2 must be at least 1kΩ. Using higher values, up to 10kΩ, will decrease power consumption during programming, but may interfere with high speed programming rates. Traces connecting PGC and PGD pins must be kept as short as possible. If longer traces are needed, it is best not to run them parallel to each other. Do not connect any diodes or capacitors to PGC or PGD pins.
PGC and PGD pins
If your PIC has several pairs of PGD/PGC pins, you can use any pair, but you must use it as a pair. Do not combine pins from different pairs.
PGC or PGD pins are busy during programming and debugging. However, you can use them during run time.
To use PGC and PGD as inputs, connect them to the source through resistors. Resistors must be at least 10kΩ (more if values of R1/R2 were increased above 1kΩ). Resistors must be connected directly to PIC's PGC or PGD pins, not to corresponding NSDSP's pins. Configure NSDSP to put PGC and PGD pins into the high impedance state while not in use. Otherwise NSDSP will drive these pins.
To use PGC and PGD as outputs, connect them directly or through protective resistors. Combined impendance must be at least 10kΩ (more if values of R1/R2 were increased above 1kΩ). Configure NSDSP to put PGC and PGD pins into the high impedance state while not in use. Otherwise NSDSP will drive these pins causing power dissipation through R1 or R2. Make sure that devices connected to these pins can tolerate high frequency signaling during programming or debugging.
To use PGC and PGD to detect USB state, configure NSDSP to alter the state of the pins depending on USB state. Once configured, you can read the state of these pins to detect when USB connection is established, and when NSDSP enters UART mode.
If not using PGC and PGD configure them as inputs. Configure NSDSP to drive both pins low when not in use.
NSDSP will drive MCLR pin high at all times (except when programming or debugging). Therefore, you can omit any MCLR circuicity that would otherwise be necessary to keep MCLR high. If your PIC does not have an internal pull-up on the MCLR, you may consider adding 100kΩ pull-down resistor to the MCLR line to prevent MCLR going high until NSDSP is fully functional
If your PIC device allows using MCLR as a GP input, you must enable MCLRE and LVP configuration bits.
To communicate with the host computer through USB, your PIC can use UART. RX and TX pins must be connected as shown. Also USB ground, NSDSP ground and PIC ground must be connected together. When not in use, NSDSP drives its TX pin high at all times.
If UART is not needed, leave NSDSP's TX pin unconnected, and connect its RX to VDD.
If UART flow control is required, RTS and CTS pins must be connected too. While NSDSP is not in the UART mode with flow control, the state of RTS is undefined. If flow control is not needed, leave NSDSP's RTS unconnected and connect CTS to ground.
For more details on UART communicatons, click here
There may be special considerations for your specific PIC device. Please visit the Supported Devices section, find your device and read the documentation.
To order pre-programmed NSDSP chips for 3.3V configurations, click on one of the links below.
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