I'm trying to operate an r/c robot with joystick and a raspberry pi running Debian and an nrf24l01 to communicate the joystick commands to the arduino on the robot. I only really need forward/back left and right, but eventually i want to put a bunch of stuff on this robot so it needs to be expandable. I'm using the nrf24 because i want to keep latency down, and it uses less power than a wifi chip. Eventually, I want to send all the axis values, some of the buttons, and the hat values to the arduino, but to test im only sending axis values.
Raspberry Pi code: (important parts are init statements on top, 128-134, and 177-180)
import RPi.GPIO as GPIO
from lib_nrf24 import NRF24
import spidev
import pygame
import time
import array
# Define some colors
BLACK = ( 0, 0, 0)
WHITE = ( 255, 255, 255)
# This is a simple class that will help us print to the screen
# It has nothing to do with the joysticks, just outputting the
# information.
class TextPrint:
def __init__(self):
self.reset()
self.font = pygame.font.Font(None, 20)
def Print(self, screen, textString):
textBitmap = self.font.render(textString, True, BLACK)
screen.blit(textBitmap, [self.x, self.y])
self.y += self.line_height
def reset(self):
self.x = 10
self.y = 10
self.line_height = 15
def indent(self):
self.x += 10
def unindent(self):
self.x -= 10
pygame.init()
# Initialize the GPIO interface
GPIO.setmode(GPIO.BCM)
# Set the width and height of the screen [width,height]
size = [500, 500]
screen = pygame.display.set_mode(size)
pygame.display.set_caption("joystick test app")
#Loop until the user clicks the close button.
done = False
# Used to manage how fast the screen updates
clock = pygame.time.Clock()
# Initialize the joysticks
pygame.joystick.init()
# Get ready to print
textPrint = TextPrint()
# Make an ouput array
output = list("test")
# Start the radio
pipes = [[0xE8, 0xE8, 0xF0, 0xF0, 0xE1], [0xF0, 0xF0, 0xF0, 0xF0, 0xE1]]
radio = NRF24(GPIO, spidev.SpiDev())
radio.begin(0, 17)
radio.setPayloadSize(32)
radio.setChannel(0x76)
radio.setDataRate(NRF24.BR_250KBPS)
radio.setPALevel(NRF24.PA_MAX)
radio.setAutoAck(True)
radio.enableDynamicPayloads()
radio.enableAckPayload()
radio.openWritingPipe(pipes[0])
radio.openReadingPipe(1, pipes[1])
radio.printDetails()
# -------- Main Program Loop -----------
while done==False:
# create array for output
# EVENT PROCESSING STEP
for event in pygame.event.get(): # User did something
if event.type == pygame.QUIT: # If user clicked close
done=True # Flag that we are done so we exit this loop
# Possible joystick actions: JOYAXISMOTION JOYBALLMOTION JOYBUTTONDOWN JOYBUTTONUP JOYHATMOTION
if event.type == pygame.JOYBUTTONDOWN:
print("Joystick button pressed.")
if event.type == pygame.JOYBUTTONUP:
print("Joystick button released.")
# DRAWING STEP
# First, clear the screen to white. Don't put other drawing commands
# above this, or they will be erased with this command.
screen.fill(WHITE)
textPrint.reset()
# Get count of joysticks
joystick_count = pygame.joystick.get_count()
textPrint.Print(screen, "Number of joysticks: {}".format(joystick_count) )
textPrint.indent()
# For each joystick:
for i in range(joystick_count):
joystick = pygame.joystick.Joystick(i)
joystick.init()
textPrint.Print(screen, "Joystick {}".format(i) )
textPrint.indent()
# Get the name from the OS for the controller/joystick
name = joystick.get_name()
textPrint.Print(screen, "Joystick name: {}".format(name) )
# Usually axis run in pairs, up/down for one, and left/right for
# the other.
axes = joystick.get_numaxes()
textPrint.Print(screen, "Number of axes: {}".format(axes) )
textPrint.indent()
axisvals = []
for i in range( axes ):
axis = joystick.get_axis( i )
textPrint.Print(screen, "Axis {} value: {:>6.3f}".format(i, axis) )
axis = (axis+1)/2
axis = int(axis * 179)
axisvals.append(axis)
output.append(chr(axis))
textPrint.unindent()
buttons = joystick.get_numbuttons()
textPrint.Print(screen, "Number of buttons: {}".format(buttons) )
textPrint.indent()
buttonvals = []
for i in range( buttons ):
button = joystick.get_button( i )
textPrint.Print(screen, "Button {:>2} value: {}".format(i,button) )
buttonvals.append(button)
# output.append(chr(button)) for now, im only sending the axis data
textPrint.unindent()
# Hat switch. All or nothing for direction, not like joysticks.
# Value comes back in an array.
hats = joystick.get_numhats()
textPrint.Print(screen, "Number of hats: {}".format(hats) )
textPrint.indent()
hatvals = []
for i in range( hats ):
hat = joystick.get_hat( i )
textPrint.Print(screen, "Hat {} value: {}".format(i, str(hat)) )
hat = str(hat)
x,y=hat.split(",") #hats is given as a strign (x, y) so we split it
if x.find("0")>=0: # only possible values are 1, 0, -1, so we search both halves
hatvals.append(int(0))
elif x.find("-")>=0:
hatvals.append(int(-1))
else:
hatvals.append(int(1))
if y.find("0")>=0:
hatvals.append(int(0))
elif y.find("-")>=0:
hatvals.append(int(-1))
else:
hatvals.append(int(1))
textPrint.unindent()
radio.flush_tx()
while (len(output) < 32):
output.append(0)
radio.write(output)
time.sleep(.005)
# ALL CODE TO DRAW SHOULD GO ABOVE THIS COMMENT
# Go ahead and update the screen with what we've drawn.
pygame.display.flip()
# Limit to 20 frames per second
clock.tick(20)
# Close the window and quit.
# If you forget this line, the program will 'hang'
# on exit if running from IDLE.
pygame.quit ()
Arduino code:
#include<SPI.h>
#include<RF24.h>
// CE, CSN pins
RF24 radio(9, 10);
void setup(void){
while(!Serial);
Serial.begin(9600);
radio.begin();
radio.setPALevel(RF24_PA_MAX);
radio.setChannel(0x76);
radio.openWritingPipe(0xF0F0F0F0E1LL);
const uint64_t pipe = (0xE8E8F0F0E1LL);
radio.openReadingPipe(1, pipe);
radio.enableDynamicPayloads();
radio.powerUp();
}
void loop(void){
radio.startListening();
Serial.println("Starting loop. Radio on.");
char receivedMessage[32] = {0};
if(radio.available()){
radio.read(receivedMessage, sizeof(receivedMessage));
Serial.println(receivedMessage);
} else {
Serial.println("No data!");
}
delay(100);
}
I have the arduino and pi communicating already, he code from this guide (http://invent.module143.com/daskal_tutorial/rpi-3-tutorial-14-wireless-pi-to-arduino-communication-with-nrf24l01/) worked flawlessly, both tests he ran. I pretty much copied all the radio init statements into the joystick code i had, and it doesn't quite work. There are two problems: When i run it, the arduino only prints: 'YYYYYYYYY', regardless of the joystick changing. It also doesn't stop printing that message after i stop the script on the Pi. The second problem is a bit worse; after running the code for a minute or so, the terminal throws an error:
Traceback (most recent call last):
File "joystick_test.py", line 180, in <module>
radio.write(output)
File "/home/pi/Desktop/NRF24L01/lib_nrf24.py", line 452, in write
self.startWrite(buf)
File "/home/pi/Desktop/NRF24L01/lib_nrf24.py", line 485, in startWrite
self.write_payload(buf)
File "/home/pi/Desktop/NRF24L01/lib_nrf24.py", line 268, in write_payload
return self.spidev.xfer2(txbuffer)
OverflowError: Argument list size exceeds 4096 bytes.
despite the line 'radio.flush_tx()' on line 177, and the sleep afterwards.
I think the first problem has to do with the way variable work between cpp and python. Honestly, i have no idea about the difference between the two, but the axis value im sending is between 0-179. In the end, I'm only turning some servos on the other side, i really don't need to send something so complicated.
The other error, i think, actually stems from the first. The transmit buffer is probably overflowing because of something with the variable storage. But i don't see what wrong with my code.
