c microcontroller oscilloscope pcb python xmega

MiniOscilloscope

Design and implementation of a miniature oscilloscope module with a usb interface. The main use of the module is monitoring the signals SPI and I2C interfaces. The repository is a patchwork of files that makes entire project. More accurate information about the project can be found in the ./docs/ (unfortunately Polish language)

Project of the MiniOscilloscope includes:

PCB design and assembly,
program for XMEAGA 32A4-AU microcontroller written in C,
GUI run on PC written in Python,
system tests.

Requirements

Acquisition parameters:

time resolution of at least 15 samples per clock cycle (SPI / I2C)
8bit voltage resolution
input voltage range 0 - 3.3V
two channels
trigger signal input
trigger mode: normal

Parameters of the printed circuit:

minimum sizes
two-layer
elements on one side of PCB
possibility of manual PCB assembly

Electrical parameters:

power supply from USB
surge protection

User application:

displays observed signals in real time
allows you to manipulate presented graph
allows you to stop/start acquisition Other:
minimal construction cost
data transmission to PC using the USB interface
test signal output

System architecture

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MiniOscilloscope module

Schematic

BOM

PCB design

The PCB was designed in accordance with the assumptions set in Requirements paragraph. Parameters of the printed circuit:

dimensions: 22 x 32 mm,
two-layer circuit,
min track width: 8 mil
min space between tracks: 6 mil
min hole: 0.45 mm
min border: 11 mil
descriptions: TOP layer

Microcontroller program

Complete source code in ./source/Xmega/

int main(void)
{
	sysclk_init();
	pmic_init();
	adc_init();
	dma_init();
	evsys_init();
	tc_init();
	ioport_init();
	
	ioport_set_pin_dir(IO_TRIGGER, IOPORT_DIR_INPUT);
	ioport_set_pin_mode(IO_TRIGGER, IOPORT_MODE_PULLUP);
	ioport_set_pin_dir(IO_CTRL_LED, IOPORT_DIR_OUTPUT);
	
	cpu_irq_enable();
	adc_enable(&ADCA);
	pwm_enable();
	udc_start();
	
	while (1)
	{
		while(!udi_cdc_getc());
		while (0 == ioport_get_pin_level(IO_TRIGGER));
		while (1 == ioport_get_pin_level(IO_TRIGGER));
		
		dma_channel_enable(DMA_CHANNEL_0);
		dma_channel_enable(DMA_CHANNEL_1);

		if (udi_cdc_is_tx_ready())
		{
			while(dma_channel_is_busy(DMA_CHANNEL_1));
			udi_cdc_write_buf(&buffer_samples, RAM_BUFFER_SIZE_2000);
			ioport_toggle_pin_level(IO_CTRL_LED);
		}
	}
}

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User application

Complete source code in ./source/Gui/

from Gui import *
import serial

SAMPLES_NR=1000
CHANNEL_NR=2

serial_port = serial.Serial(port = 'COM3', write_timeout=0.1, inter_byte_timeout=0.1)
serial_port.flushInput()
RTS= bytearray(b'\xff')

gui=GUI(CHANNEL_NR,SAMPLES_NR)
paused = False

while True:

    key  = gui.get_key()
    if key == ' ':
        paused = not paused
        gui.toggle_state()
    elif key  == 'escape':
        break

    if not paused:
        try:
            serial_port.flushInput()
            serial_port.write(RTS)
            for channel in range(CHANNEL_NR):
                buffer = serial_port.read(SAMPLES_NR)
                gui.set_y(channel, buffer)
        except:
            pass

    gui.plot()
    gui.pause()