Using pyserial with Arduino without hangs or freezes

README.md

Using pyserial with Arduino without hangs or freezes

By default pyserial doesn't play nice with Arduino. The Arduino may reset at the start of the communication or hangs after few minutes.
This application demonstrate 2MBits/sec serial communication with an Arduino UNO (ATMega328) to drive 56 APA102 LEDs. This code can achieve a refresh rate of ~100Hz and can run forever with no hangs or freezes.

Installing pyserial

pip install pyserial

led_driver.ino

#include <FastGPIO.h>
#define APA102_USE_FAST_GPIO
#include <APA102.h>

#define PIN_DATA 11
#define PIN_CLOCK 12
#define NUM_LEDS 56
#define NUM_BYTES NUM_LEDS * 3

const uint8_t PROGMEM gamma8[] = {
    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,
    0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  0,  1,  1,  1,  1,
    1,  1,  1,  1,  1,  1,  1,  1,  1,  2,  2,  2,  2,  2,  2,  2,
    2,  3,  3,  3,  3,  3,  3,  3,  4,  4,  4,  4,  4,  5,  5,  5,
    5,  6,  6,  6,  6,  7,  7,  7,  7,  8,  8,  8,  9,  9,  9, 10,
   10, 10, 11, 11, 11, 12, 12, 13, 13, 13, 14, 14, 15, 15, 16, 16,
   17, 17, 18, 18, 19, 19, 20, 20, 21, 21, 22, 22, 23, 24, 24, 25,
   25, 26, 27, 27, 28, 29, 29, 30, 31, 32, 32, 33, 34, 35, 35, 36,
   37, 38, 39, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 50,
   51, 52, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 66, 67, 68,
   69, 70, 72, 73, 74, 75, 77, 78, 79, 81, 82, 83, 85, 86, 87, 89,
   90, 92, 93, 95, 96, 98, 99,101,102,104,105,107,109,110,112,114,
  115,117,119,120,122,124,126,127,129,131,133,135,137,138,140,142,
  144,146,148,150,152,154,156,158,160,162,164,167,169,171,173,175,
  177,180,182,184,186,189,191,193,196,198,200,203,205,208,210,213,
  215,218,220,223,225,228,231,233,236,239,241,244,247,249,252,255 };

APA102<PIN_DATA, PIN_CLOCK> Strip;
char buffer[512];
rgb_color leds[NUM_LEDS];

void setup(){
    Serial.begin(2000000);
    leds[0] = rgb_color(0, 255, 30);
    Strip.write(leds, NUM_LEDS);
}

void loop(){
    if (Serial.available()) {
        char read = Serial.readBytes(buffer, NUM_BYTES);
        while(Serial.available() > 0) {
            char t = Serial.read();
        }
        Serial.println(read);
        for (int i = 0; i < NUM_LEDS; ++i){
            leds[i] = rgb_color(
                                (uint8_t) pgm_read_byte(&gamma8[(uint8_t) buffer[3*i]]),
                                (uint8_t) pgm_read_byte(&gamma8[(uint8_t) buffer[3*i+1]]),
                                (uint8_t) pgm_read_byte(&gamma8[(uint8_t) buffer[3*i+2]]));
        }
        Strip.write(leds, NUM_LEDS);
    }
}

led_driver.py

from time import sleep
import serial
from threading import Thread
from queue import Queue

class Driver:
    def __init__(self, port_name="/dev/ttyACM0", baudrate=2000000, led_count=56):
        self.frame_q = Queue(maxsize=0)
        self.port_name = port_name
        self.led_count = led_count
        self.baudrate = baudrate
        self.running = True
        Thread(target=self.handle_serial).start()
        sleep(1)

    def close(self):
        self.running = False

    def __len__(self):
        return self.led_count

    def handle_serial(self):
        port = serial.Serial()
        port.port = self.port_name
        port.baudrate = self.baudrate

        port.bytesize = serial.EIGHTBITS
        port.parity = serial.PARITY_NONE
        port.stopbits = serial.STOPBITS_ONE
        port.xonxoff = False
        port.rtscts = False
        port.dtr = False
        port.timeout = 1
        port.write_timeout = 1
        port.open()

        while self.running:
            if not self.frame_q.empty():
                port.write(self.frame_q.get())
                port.flush()
            port.reset_input_buffer()
            port.reset_output_buffer()
            pass

        port.close()

    def to_bytes(self, leds):
        ba = bytearray([])
        for l in leds:
            ba = ba + bytearray(l)
        return ba

    def set_leds(self, l):
        self.frame_q.put(self.to_bytes(l))