While the wind’s too breezy and the temperature’s too cool to work on Hermione remote control, I’ve been working on the servo robot tutorial for the Cotswold Raspberry Jam on Saturday 19th May 1pm – 4pm at Cheltenham UoG.
Servo motors
Tickets are free, the tutorial are free, the take-home kit is free – if you’re vaguely in the Cotswolds are, come along!
courtesy of @RPiSpy
…celebrating the Raspberry Pi 6th Birthday. I’m now packing her away into safe keeping until the day.
P.S. Her instability was purely down to her batteries being too darn cold
So there I was this morning on the bus heading to Cheltenham to co-host the Cotswold Raspberry Jam, gazing at the beautiful Cotswold countryside, and my mind began to wander – well actually it was unleashed from the constraints of dealing with details it couldn’t fix while on a bus. And out came a better idea about where to go for the next step to autonomy.
What’s been bugging me is the difference between magnetic and GPS North. The ‘bus’ solution is to ignore magnetic north completely. The compass still has a role to play maintaining zero yaw throughout a long flight, but it plays no part in the direction of flight – in fact, this is mandatory for the rest of the plan to work.
Instead, the autopilot translates between GPS north, south, east and west coordinate system and Hermione’s forward, backwards, right and left coordinate. The autopilot only speaks to Hermione in her own coordinates when telling her where to go. The autopilot learns Hermione’s coordinate system at the start of each flight by asking her to fly forwards a meter or so, and comparing that to the GPS vector change it gets. This rough translation is refined continuously throughout the flight. Hermione can start a flight pointing in any direction compared to the target GPS point, and the autopilot will get her to fly towards the GPS target regardless of the way she’s pointing.
Sadly now, I’m back from today’s Jam, and the details confront me once more, but the bus ride did yield a great view of where to go next.
P.S. As always, the jam was great; over 100 parents and kids, lots of cool things for them to see and do, including a visit this time by 2 members of local BBC micro:bit clubs. Next one is 30th September.
Just using spare time to put together a tutorial for the Autumn Cotswold Raspberry Jam.
import RPi.GPIO as GPIO
import time
RED_LED = 35
GREEN_LED = 33
BLUE_LED = 37
GPIO.setmode(GPIO.BOARD)
GPIO.setup(RED_LED, GPIO.OUT)
GPIO.setup(GREEN_LED, GPIO.OUT)
GPIO.setup(BLUE_LED, GPIO.OUT)
GPIO.output(RED_LED, GPIO.LOW)
GPIO.output(GREEN_LED, GPIO.LOW)
GPIO.output(BLUE_LED, GPIO.LOW)
#---------------------------------------------------------------
# All the LEDs are turned on every 1/100 of a second or 0.01s.
#---------------------------------------------------------------
pulse_period = 0.01
#---------------------------------------------------------------
# This is how much of the pulse period each LED stays turned on.
# After that, it gets turned off again.
#---------------------------------------------------------------
red_fraction = 0.002
red_on = red_fraction
blue_fraction = 0.003
blue_on = blue_fraction
green_fraction = 0.005
green_on = green_fraction
#---------------------------------------------------------------
# Remember the time this all started so we can work out how long
# we've been going since we started.
#---------------------------------------------------------------
start_time = time.time()
try:
while True:
time.sleep(0.001)
clock_time = (time.time() - start_time) % pulse_period
#========================== RED =======================#
if clock_time < red_on * pulse_period: GPIO.output(RED_LED, GPIO.HIGH) else: GPIO.output(RED_LED, GPIO.LOW) red_on += red_fraction if red_on > 1 or red_on < 0:
red_fraction = -red_fraction
red_on += red_fraction
#========================= GREEN ======================#
if clock_time < green_on * pulse_period: GPIO.output(GREEN_LED, GPIO.HIGH) else: GPIO.output(GREEN_LED, GPIO.LOW) green_on += green_fraction if green_on > 1 or green_on < 0:
green_fraction = -green_fraction
green_on += green_fraction
#========================= BLUE =======================#
if clock_time < blue_on * pulse_period: GPIO.output(BLUE_LED, GPIO.HIGH) else: GPIO.output(BLUE_LED, GPIO.LOW) blue_on += blue_fraction if blue_on > 1 or blue_on < 0:
blue_fraction = -blue_fraction
blue_on += blue_fraction
except KeyboardInterrupt as e:
pass
GPIO.output(RED_LED, GPIO.LOW)
GPIO.output(GREEN_LED, GPIO.LOW)
GPIO.output(BLUE_LED, GPIO.LOW)
GPIO.cleanup()
Infamy me is at 2:23 but there’s much more worth seeing about the CotswoldJam items like the @davejavupride at 0:16 and 2:02 and @CotswoldJam at 0:48 and 1:15 with @aroakley. The next Cotswold Jam is on 25th March. Be there or be square!
Bloomberg HelloWorld published their programme on English technology yesterday.
Zoe only appears at 2:18 for a fraction of a second, despite a 2 hour chat I had with these guys; on the plus side, they did take my advice and visit the Cotswold Raspberry Jam where they found David Pride and his amazing creations – have a look at 7:25 onwards and again at 11:12.
me trying to convince the audience (there were more than it looks like) how video macro-blocks could be used for lateral motion tracking (and more speculatively, vertical and rotational too).
Me and my Vanity
There are lots more photos of yesterday’s Cotswold Raspberry Jam that aren’t soiled by my presence on facebook – check ’em out at (or even better, join) the Cotswold Jam group or follow us on Twitter.
The next Cotswold Jam with be on 26th November from 1 – 4 at the University of Gloucestershire, Park Campus, Cheltenham.