LCD TFT OSCILLOSCOPE

The USB Oscilloscope project is moved to this page

Updated 5.8.2015.
LCD TFT is digital display at its best, it displays versatile clear picture. The picture is built by entering the address and the color of a pixel or rectangle, so it's simple to use too.
LCD TFT low frequency oscilloscope, bandwidth is DC to 1000Hz. Max sampling rate is 16000 samples per second. An oscilloscope with these specifications has limited use, but it is a good exercise in using LCD TFT.
The circuit is powered by 5V. 74HC4050 hex buffer can be replaced by 4050B cmos. The power to PIC16F690 is 3.3V. you can use the 3.3V supply from the TFT Module or add an external 3.3V regulator.
The screen is constructed from 80 sampling. The ADC reads the input at resolution of 10 bits. The MSB 8 bits are stored in the pic RAM and then transmitted to the LCD RAM by 4 wires SPI.
The time selector has 100ms per screen, 10ms and the third position is about 5ms. The trigger is done by software and can be switched off.
LCD TFT modules vary depending on the drive IC. The module in the project has the driver ST7735 or S6D02A1A01. I bought this module directly from China because the price was more sensible.
Code was written on MPLAB and compiled with the free HI TECH C compiler V9.80
Software includes PIC code . You are free to use the circuit diagram and the software with no limitations.

The LCD TFT Module

Circuit Description
See also Technical Tips

PIC16F690
Pin 8 is the analogue input. Input voltage range is 0 to 3.3V absolute max, voltage outside this range can latch the input or even permanently damage the IC.
The clock is 8MHz by the internal osc.
3.3V to the pic can be connected to the 3.3V regulator on the TFT module, or external regulated 3.3V.
The module in the project has the driver ic ST7735. If you use module with driver ic S6D02A1A01 you will need to uncomment the inversion command in the code to stop it inverting colors.

Circuit Description
See also Technical Tips

PIC16F876A
Pin 2 is the analogue input. Input voltage range is 0 to 5V absolute max, voltage outside this range can latch the input or even permanently damage the IC.
The clock is 8MHz by the crystal osc.
3.3V to the 74HC4050 can be connected to the 3.3V regulator on the TFT module.
74HC4050 hex buffer is level shift to drop the 5V from the pic outputs to 3.3V input to the TFT Module. You can use cmos 4050B. If you use another buffer make sure it has 5V tolerant inputs.
The module in the project has the driver ic S6D02A1A01. If you use module with driver ic ST7735 you will need to comment the inversion command in the code to stop it inverting colors.