Full Circuit

The source and firmware for the circuit can be found at the bottom of the page. Each section of the circuit is labeled in the schematic. All of the sections and their components are described and discussed below. The part numbers for the components are linked to websites for data and more information when available.

Power Supply

The power supply uses a 9 volt battery and a TC1262-5.0V high-accuracy low-dropout linear voltage regulator to provide a stable 5 volt supply for the microcontroller and the graphical LCD. A 1uF (microFarad) polarized decoupling capacitor is necessary on the output of the voltage regulator to prevent power spikes or ripples. A wall wart power supply as low as 5.3V can be substituted for the 9 Volt battery.

AZ Displays AGM1264F

The AGM1264F is 128 x 64 pixel graphical LCD with built in controllers that allow is to be easily controlled using a PIC microcontroller. It is a 128 x 64 pixel graphical LCD and has an LED backlight, onboard negative voltage generator (LMC7660) for LCD driving, onboard Samsung KS0108 controller, and an 8-Bit MPU interface.

Analog Input

The 1st analog input (Pin A0) is configured to be an analog input. Please note that “The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kΩ.” (PIC18F2550, p.260)

Microcontroller

The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is not used in this project. The component marked ‘RES’ is a 20MHz resonator.

RS232 Level Converter

The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.

Source and Firmware
The PIC must initially programmed with the ‘SAC_tinybld18F2550usb _20MHz_115200_48MHz’ hex file to program the bootloader on the PIC. Then, using Tiny PIC Bootloader, the hex file can be placed on the chip using the Tiny PIC Bootloader frontend with ’12h 34h 56h 78h 90h’ in the ‘List of codes to send first:’ in the ‘Options’ menu. Please feel free to contact me if you have any problems.

• SAC_tinybld18F2550usb_20MHz_115200_48MHz.hex
• 18F2550 GLCD Oscilloscope DR1r1.c (hex)
• GLCD – modified.c

Videos
Here are three videos of the PIC18F2550 GLCD Oscilloscope in action. The first video demonstrates sine, triangle, and square waves of different frequencies. The second video demonstrates different waves with shifting amplitudes and offsets. The third video compares the display of the PIC18F2550 GLCD Oscilloscope to the display of a Hewlett Packard 54603B oscilloscope.

Update (November 15, 2006)
Here is the firmware without the bootloader code:

• 18F2550 GLCD Oscilloscope DR1r1 – no bootloader.c (hex)

Update (February 1, 2007)
Here is untested firmware for the PIC18F4550 without the bootloader code:

• 18F4550 GLCD Oscilloscope DR1r1 – no bootloader.c (hex)

Update (April 11, 2007)
Here is untested firmware for the PIC18F252 and PIC18F452 without the bootloader code. Please note that you will need to use a 10MHz crystal/resonator instead of a 20MHz one.

• 18F252 GLCD Oscilloscope DR1r1 – no bootloader.c (hex)
• 18F452 GLCD Oscilloscope DR1r1 – no bootloader.c (hex)

Full Circuit

The source and firmware for the circuit can be found at the bottom of the page. Each section of the circuit is labeled in the schematic. All of the sections and their components are described and discussed below. The part numbers for the components are linked to websites for data and more information when available.

Power Supply

The power supply uses a 9 volt battery and a TC1262-5.0V high-accuracy low-dropout linear voltage regulator to provide a stable 5 volt supply for the microcontroller and the MAX114. A 1uF (microFarad) polarized decoupling capacitor is necessary on the output of the voltage regulator to prevent power spikes or ripples. A wall wart power supply as low as 5.3V can be substituted for the 9 Volt battery.

Analog Input

The analog input is connected to the A0 pin on the PIC, which is configured to be an analog input, and the IN1, IN2, IN3, and IN4 pins on the MAX114. Please note that for the PIC, “The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kΩ” (PIC18F2550, pp. 260). In addition, please note that for the MAX114, “The typical 32pF input capacitance allows source resistance as high as 800 Ohms without setup problems. For larger resistances, the acquisition time (tACQ) must be increased.” (MAX114, pp. 10).

MAX114

The MAX114 is a “microprocessor-compatible, 8-bit, 4-channel … analog-to-digital converter (ADC). [It] operates from a single +5V supply and uses a half-flash technique to achieve a 660ns conversion time (1Msps).” (MAX114, pp. 1). The MAX114 is a high-speed ADC that allows for multi-channel data acquisition with minimal processor overhead. The bypass capacitors (C2 and C3) are necessary to minimize power input fluctuations.

Microcontroller

The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is not used in this project. The component marked ‘RES’ is a 20MHz resonator.

RS232 Level Converter

The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.

Source and Firmware

The PIC must initially programmed with the ‘SAC_tinybld18F2550usb _20MHz_115200_48MHz’ hex file to program the bootloader on the PIC. Then, using Tiny PIC Bootloader, the hex file can be placed on the chip using the Tiny PIC Bootloader frontend with ’12h 34h 56h 78h 90h’ in the ‘List of codes to send first:’ in the ‘Options’ menu. Please feel free to contact me if you have any problems.
– SAC_tinybld18F2550usb_20MHz_115200_48MHz.hex
– 18F2550 MAX114.c (hex)

Full Circuit

The source and firmware for the circuit can be found at the bottom of the page. Each section of the circuit is labeled in the schematic. All of the sections and their components are described and discussed below. The part numbers for the components are linked to websites for data and more information when available.

Power Supply

The power supply uses a 9 volt battery and a TC1262-5.0V high-accuracy low-dropout linear voltage regulator to provide a stable 5 volt supply for the microcontroller and the MAX144. A 1uF (microFarad) polarized decoupling capacitor is necessary on the output of the voltage regulator to prevent power spikes or ripples. A wall wart power supply as low as 5.3V can be substituted for the 9 Volt battery.

Analog Input

The analog input is connected to the A0 pin on the PIC, which is configured to be an analog input, and the CH0 and CH1 pins on the MAX144. Please note that for the PIC, “The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kΩ” (PIC18F2550, pp. 260). In addition, please note that for the MAX144, “The acquisition time, tACQ, is the maximum time the device takes to acquire the signal, and is also the minimum time required for the signal to be acquired. Calculate this with the following equation: tACQ = 9(RS + RIN)CIN where RS is the source impedance of the input signal, RIN (9k) is the input resistance, and CIN (16pF) is the input capacitance of the ADC. Source impedances below 1k have no significant impact on the AC performance of the MAX144/MAX145” (MAX144, pp. 8).

MAX144

The MAX144 is a “Low-power, 12-bit analog-to-digital converter (ADC) … [that operates] with a single +2.7V to +5.25V supply and features a 7.4μs successive-approximation ADC, automatic power-down, fast wake-up (2.5μs), an on-chip clock, and a high-speed, 3-wire serial interface” (MAX144, pp. 1). The bypass capacitors (C2 and C3) are necessary to minimize power input fluctuations.

Microcontroller

The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is not used in this project. The component marked ‘RES’ is a 20MHz resonator.

RS232 Level Converter

The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.

Source and Firmware

The PIC must initially programmed with the ‘SAC_tinybld18F2550usb _20MHz_115200_48MHz’ hex file to program the bootloader on the PIC. Then, using Tiny PIC Bootloader, the hex file can be placed on the chip using the Tiny PIC Bootloader frontend with ’12h 34h 56h 78h 90h’ in the ‘List of codes to send first:’ in the ‘Options’ menu. Please feel free to contact me if you have any problems.
– SAC_tinybld18F2550usb_20MHz_115200_48MHz
– 18F2550 MAX144 SPI.c (hex)
– 18F2550 MAX144 int16.c (hex)

Full Circuit

The source and firmware for the circuit can be found at the bottom of the page. Each section of the circuit is labeled in the schematic. All of the sections and their components are described and discussed below. The part numbers for the components are linked to websites for data and more information when available.

Power Supply

The power supply uses a 9 volt battery and a TC1262-5.0V high-accuracy low-dropout linear voltage regulator to provide a stable 5 volt supply for the microcontroller and the MAX1241. A 1uF (microFarad) polarized decoupling capacitor is necessary on the output of the voltage regulator to prevent power spikes or ripples. A wall wart power supply as low as 5.3V can be substituted for the 9 Volt battery.

Analog Input

The analog input is connected to the A0 pin on the PIC, which is configured to be an analog input, and the AIN pin on the MAX1241. Please note that for the PIC, “The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kΩ” (PIC18F2550, pp. 260). In addition, please note that for the MAX1241, “Acquisition time is calculated by: tACQ = 9(RS + RIN) x 16pF where RIN = 9k, RS = the input signalâ€s source impedance, and tACQ is never less than 1.5µs. Source impedances below 1k do not significantly affect the ADCâ€s AC performance” (MAX1241, pp. 8 ).

MAX1241

The MAX1241 is a “Low-power, 12-bit analog-to-digital converter (ADC) … [That] operates with a single +2.7V to +5.25V supply. [The MAX1241 features] a 7.5µs successive-approximation ADC, a fast track/hold (1.5µs), an on-chip clock, and a high-speed, 3-wire serial interface” (MAX1241, pp. 1). The bypass capacitors (C2, C3, and C5) are necessary to minimize power input fluctuations.

Microcontroller

The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is not used in this project. The component marked ‘RES’ is a 20MHz resonator.

RS232 Level Converter

The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.

Source and Firmware

The PIC must initially programmed with the ‘SAC_tinybld18F2550usb _20MHz_115200_48MHz’ hex file to program the bootloader on the PIC. Then, using Tiny PIC Bootloader, the hex file can be placed on the chip using the Tiny PIC Bootloader frontend with ’12h 34h 56h 78h 90h’ in the ‘List of codes to send first:’ in the ‘Options’ menu. Please feel free to contact me if you have any problems.
– SAC_tinybld18F2550usb_20MHz_115200_48MHz.hex
– 18F2550 MAX1241 SPI.c (hex)
– 18F2550 MAX1241 int16.c (hex)

Full Circuit
The source and firmware for the circuit can be found at the bottom of the page. Each section of the circuit is labeled in the schematic. All of the sections and their components are described and discussed below. The part numbers for the components are linked to websites for data and more information when available.

Analog Inputs
The 5 analog inputs are connected to pins A0, A1, A2, A3, and A5, which are configured to be analog inputs. Please note that “The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kOhms.” (PIC18F2550, p.260)

Digital Inputs/Outputs
The digital inputs and outputs share Port B. Please note that:
Maximum output current sunk by any I/O pin = 25 mA
Maximum output current sourced by any I/O pin = 25 mA
Maximum current sunk by all ports = 200 mA
Maximum current sourced by all ports = 200 mA

Microcontroller
The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is used in this project. The component marked ‘RES’ is a 20MHz resonator.

RS232 Level Converter
The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.

USB I/O
The PIC is connected to the computer through a USB port and is bus-powered.

Source and Firmware
The PIC must initially programmed with the ‘SAC_tinybld18F2550usb _20MHz_115200_48MHz’ hex file to program the bootloader on the PIC. Then, using Tiny PIC Bootloader, the hex file can be placed on the chip using the Tiny PIC Bootloader frontend with ’12h 34h 56h 78h 90h’ in the ‘List of codes to send first:’ in the ‘Options’ menu. Please feel free to contact me if you have any problems.

• SAC_tinybld18F2550usb_20MHz_115200_48MHz.HEX
• 18F2550 USB HID CRC IO.c (hex)
• usb_desc_hid 8-byte.h
• Visual Basic example software and source code: PIC18F2550 USB HID IO VB Example.zip

Update (November 15, 2006)
Here is the firmware without the bootloader code:

• 18F2550 USB HID CRC IO – no bootloader.c (hex)

Update 2 (December 18, 2006)
Here are untested PIC18F4550 firmwares:

• 18F4550 USB HID CRC IO.c (hex)
• 18F4550 USB HID CRC IO – no bootloader.c (hex)

Full Circuit

The source and firmware for the circuit can be found at the bottom of the page. Each section of the circuit is labeled in the schematic. All of the sections and their components are described and discussed below. The part numbers for the components are linked to websites for data and more information when available.

Analog Input

The analog input for the oscilloscope is connected to the A0 pin, which is configured to be an analog input. Please note that “The source impedance affects the offset voltage at the analog input (due to pin leakage current). The maximum recommended impedance for analog sources is 2.5 kΩ” (PIC18F2550, pp. 260).

Microcontroller

The microcontroller used is a Microchip PIC18F2550. I modified the PIC18F2550 Tiny PIC Bootloader assembly file so I could use a 20MHz crystal/resonator at 115,200 baud (the modified bootloader can be found at the bottom of the page). The PIC18F2550 runs at 48MHz using the internal PLL. R1 is a pull-up resistor necessary for operation. C1 is a stabilizing capacitor that is used for the onboard USB voltage regulator, which is used in this project. The component marked ‘RES’ is a 20MHz resonator.

RS232 Level Converter

The microcontroller USART pins need to be connected to a RS-232 Level Converter to connect to a PC for firmware updates using the Tiny PIC Bootloader. Otherwise, after initial programming they can be left disconnected.

USB I/O

The PIC is connected to the computer through a USB port and is bus-powered.

Source and Firmware

The PIC must initially programmed with the ‘SAC_tinybld18F2550usb _20MHz_115200_48MHz’ hex file to program the bootloader on the PIC. Then, using Tiny PIC Bootloader, the hex file can be placed on the chip using the Tiny PIC Bootloader frontend with ’12h 34h 56h 78h 90h’ in the ‘List of codes to send first:’ in the ‘Options’ menu. Please feel free to contact me if you have any problems.
– SAC_tinybld18F2550usb_20MHz_115200_48MHz.hex
– 18F2550 USB HID CRC Oscilloscope.c (hex)
– usb_desc_hid 8-byte.h
– Visual Basic example oscilloscope software with DFT: PIC18F2550 USB HID Oscilloscope DR1r1 VB Example.zip

Example Oscilloscope Images