Saturday, 28 November 2015

Its the final countdown! - One week to go

This time next week I'll be in Cambridge participating in PiWars (Assuming no more magic smoke escapes from my robot) and I have a busy weekend planned to try and pull everything together. I've been busy doing some more soldering this morning and will be doing some more this afternoon, after visiting Maplins to get supplies!

Main focus today is to get my line sensor mounted on my newer chassis, as the previous method is no longer viable. This is going to mean moving the Arduino that controls it off the bread board and onto something more permanent. I did consider moving the sensor onto the same Arduino that drives the motors, but I just don't have enough pins spare, and it would be a little fiddly connecting it up.

After that I need to work out a mechanism for holding the 'wire' for the Pi Noon challenge, which is slightly trickier now that the motors and wheels are mounted forwards of the chassis, and then tweaking the code for the autonomous challenge.

Hopefully that will then leave tomorrow for sorting out a device to help with the Skittles challenge. I have some plans but have not had time to actually build anything!  Worse case I'll just have to give the ball a good push.

There's a few other things I want to work on, but as they are extras they can wait until later.. As for other deadlines, well the 'blogging' challenge completes today (in about 30 minutes!) to ensure there's enough time for them all to be judged before Saturday. Obviously that doesn't mean I'll stop blogging, I should have at least one post before the event that (hopefully) shows OptimusPi fully functional, and I'll have a post-PiWars update as well.

So, with the clock ticking, its back to the soldering!


Thursday, 26 November 2015

Soldiering on - Soldering on

One of the issues I've had with previous robots (and other contraptions) is managing to plug cables in the wrong way round, something that's especially easy to do when using jumper leads as they are typically not joined together and can get mixed up in oh so many ways (Not to mention the fact there's 40 pins on the Raspberry Pi to actually connect them to).

To try and avoid this happening I try to add dedicated connectors for each component, preferably of the kind that can only be plugged in one way. So last night I grabbed an Adafruit Perma-Proto Pi HAT board out of the box its been living in for the past few months and began to prod it with a hot stick (well a soldering iron).

With such small components it can be difficult to rectify an error so its best to take some time to work out what you need connecting up, and where. For OptimusPi pretty much everything connects via I2C, some components using the regular I2C pins, and the rest using GPIO pins 5 and 6. However I also need to have the SenseHAT connected, and it needs to be on top so I can get at the joystick and use the LED matrix. Due to the ways that the pins connect up on the Adafruit board that just left the one side I could easily bring connections out to.

After moving things around, trying out different connections and seeing how things looked when connected to the RPi itself I decided to have the 'external' I2C connector in the bottom right corner (above the AV connector) and the OLED in the middle (covering the HDMI port, but I don't plan on using that) which leaves room in the bottom left corner for future expansion (Maybe my RTC will end up there).

Constantly checking the connections to make sure I don't wire things up backwards I added the necessary wires to connect the GPIO pins to the correct locations on the lower half of the board and, before plugging it in, uses a multi meter to double check everything was connected as expected.

As I didn't have too many right-angled connectors in my box of bits I had to modify one of the 'straight up' connectors by lowering the pins (heating them with the soldering iron and pulling them through the plastic) and bending them with a pair of pliers. So adding the I2C connector took a little longer than it needed to. However everything was finally connected, so time to apply the power.

A couple of checks using 'i2cdetect' to make sure the OLED and SenseHAT were being correctly detected and I fired up the OptimusPi binary and was happy to see the OLED working. Of course with it mounted on the side I have to go and tweak the code so the joystick works as expected. But where does that other wire go?

Well one of the other components I picked up recently was the Grove I2C hub. which I've mounted underneath the Raspberry Pi (I may move this as, whilst its nicely hidden, its a bit of a pain to reach). This replaces the I2C 'expander' I'd home-made previously, with the added benefit of ensuring you can't connect the cables backwards.

With the Raspberry Pi all connected up I turned my attention to the Arduino controlling the motors. This time it was an Adafruit ProtoShield I soldered up, and so far only the I2C connection that I've soldered in. I actually need to go and revisit this and use a proper connector (Not sure why I didn't... was getting late!) but for now this makes it a little easier to wire everything up.

I have a few other items I want to connect up to the Arduino, if I have time that is, but for now I need to make sure all the basics are working again before adding extras.

As a reminder of how little time there is left my PiWars timetable turned up today, and about the only challenge I'm ready for is the Obstacle course!


Tuesday, 24 November 2015

'Tis but a scratch! - Up and running again

Well after carefully checking all the components everything seems to be working, apart from possibly the UBEC that was powering the Raspberry Pi.  There's no sign of burnt cables, or discolourations on the Arduino or Motor driver and after re-applying power OptimusPi happily trundles around.

There's still the issue of the motors not being mounted level, and I need to swap in a replacement UBEC (currently using an Adafruit PowerBoost board to power the Raspberry Pi) but at least I don't have to order in any replacement parts!

Speaking of which, the NFC reader I ordered back in September has finally arrived... Unfortunately its probably a little to late for me to do anything useful with it.

So with this minor panic over its back to the more general case of 'running out of time' panic! I've got some soldering to do these next few evenings, sort out the motor mounts, work out how to connect the line following sensor to this new chassis, improve the code and various other things!


Puff the magic dragon - uh-oh I see smoke...

So this blog was supposed to be about how I decided I needed a bit more room inside my robot, how I switched to a large box, mounted the motors on it, added cabling so the motors can be easily swapped out, added a power switch and generally tided things up a bit.

So many wires
Unfortunately when I was setting OptimusPi up last night to take photos I suddenly noticed smoke escaping from the inside of the box... Possibly the mythical magical smoke that makes electronics work?

Quickly cutting the power (yay for the new power switch) I popped the lid off and removed the battery to check for damage. An initial glance didn't show any burnt wiring or other damage, which implies the damage was done to the Arduino which is hidden beneath the motor driver.

I've checked the Raspberry Pi and the OLED, which both seem to be working happily, but it was getting late and I didn't have time to check the state of the Arduino, so that's something I'll have to do tonight.  Hopefully its just the Arduino that got charred, and not the motor driver, as I have a spare Arduino I can replace it with (Although not a nice, shiny, black Adafruit one). But with only 11 days to go until PiWars I have a lot of work to do.

But back to the updated robot. With the motors mounted to the base I, technically, don't need the plywood base I was using previously, however it means the robot doesn't look all that pretty. I did have plans for the top, but now I'm not sure I'll have time to get anything extra done now.

One other problem I ran into is I managed to end up with motors that aren't mounted level, so it has a bit of a wobble to it. Its something that's fixable (just takes more time) but I need a working robot first, here's hoping nothing too badly damaged.


Saturday, 14 November 2015

Job's done - Code complete-ish

Today, at noon, was the deadline for the Code Quality challenge and therefore an obvious target to have my code functionally complete (The competitors are still allowed to change code up to the main PiWars event itself). So how did I do?

To keep track of the code I submitted today I created a tag in GIT called PiWars2015-CodeChallenge so I can refer back to it later (if needed) and the stats of that code snapshot are v 1.60  T=0.17 s (297.2 files/s, 29810.7 lines/s)
Language                     files          blank        comment           code
C++                             20            583            594           1700
C/C++ Header                    21            258            422            564
Arduino Sketch                   6            131            221            340
Python                           2             44             55            162
CMake                            2             12              9             21
SUM:                            51           1028           1301           2787

So that's 51 files created and almost 2800 lines of code written... But is it complete?

In the past few weeks I've added 'ThoughtProcesses for the StraightLine and ThreePointTurn challenges. These both make use of the Sense HAT's array of sensors to determine the current heading of the robot, using it to try and maintain driving in a straight line, and for performing the turns for the three point turn. As can be seen in the following videos it doesn't always work quite right... I've tried re-calibrating the sensors a couple of times, but looks like I need to try it once more, not to mention changing the 'dead-reckoning' times to something a little more intelligent.

So, in theory, I can now enter all the autonomous challenges, although not with a huge chance of success as the code currently stands.

During testing I've been running one challenge at a time, editing the code and rebuilding it when switching between them. Obviously this is something I'd rather not have to do on the day, so I need a way of selecting between the various tasks. I had previously purchased an OLED display, but had been avoiding playing with it until I had the other functionality out of the way. Most of the example code for driving the OLED was for the Arduino so I spent some time hunting for a library that I could use from C/C++.

After wasting a bit of time searching for the wrong driver (SSD1305 instead of a SSD1306) I eventually selected the ArduiPi_OLED library to drive the display. The library does come with a few disadvantages, I now have to run my binary with 'sudo', the binary contains two library that try to access the GPIO pins and I2C bus (so far no obvious conflicts) and I can't have all my devices hanging off the same bus (which means more cables on the robot). However it has the advantage of getting things up and running now, which is useful when you have a deadline!

With the display working I added a 'Menu' class, updated the main PiWars class to create and display a menu, and to update all the ThoughtProcesses so they can be run in a background thread to not block the main thread. To navigate the menu's I'm making use of the joystick on the Sense HAT, as that will always be connected (the PS3 joystick may not be) and is simple to use. The results of all this work can be seen below

With the menu system I can select all the supported functionality, as well as shutting down the robot correctly, without yanking the power out and risking file system corruption.

So with three weeks what's left to do?  There's a couple of nice-to-have items that are just not going to make it (My RFID reader has been on back order for 2 months now, it may arrive before December but no time to add it) so I'll be spending the rest of the time tweaking my code,, practising driving and making the robot pretty, not necessarily in that order!