Firmware¶

Sketches for the microcontrollers, in the firmware/ folder of the repository.

Tactile maze: gratings and reward ports¶

firmware/arduino/servo_control/servo_control.ino runs the whole tactile rig. It listens for text commands on the serial port and drives ten servos through an Adafruit PCA9685 sixteen-channel PWM controller, plus four infrared detectors.

It needs two Arduino libraries:

Command protocol¶

Command	Effect
`grt<name> <angle>`	Turn grating `<name>` to `<angle>`, for example `grtLL 90`
`rew<arm>`	Run the reward routine for arm `A` to `D`, for example `rewA`

Angles are given in a 0 to 120 range, which the sketch maps onto the servo's pulse limits. The session sets every grating to 0 at the start of a trial, then sends the positions for that trial's reward location.

Grating channels¶

Three pairs, one before each decision point of the two-level tree.

Channel	Name	Position
0	`L`	First junction, left
1	`R`	First junction, right
4	`LL`	Left second junction, left
2	`LR`	Left second junction, right
3	`RL`	Right second junction, left
5	`RR`	Right second junction, right

Channels 12 to 15 carry LLL, LRR, RLL and RRR for a three-level maze. The firmware accepts them; the two-level configuration does not use them.

The grating servos are Pololu FS90 micro servos, and the pulse limits at the top of the sketch (GRATSERVOMIN, GRATSERVOMAX) are set for that model. Fit a different servo and those need adjusting.

Reward ports¶

Each arm pairs a servo with an infrared detector across the pellet chute.

Arm	Servo channel	IR sensor pin
A	8	2
B	9	15
C	7	17
D	6	16

The routine is closed-loop. The servo rocks the dispenser between two positions while the sketch watches the infrared input, and it keeps rocking until the beam reads broken, which means a pellet has physically fallen through. Then it stops.

flowchart LR
    C[rewA received] --> P1[Servo to position 1]
    P1 --> W1{Beam broken<br/>within the window?}
    W1 -->|yes| Stop[Stop]
    W1 -->|no| P2[Servo to position 2]
    P2 --> W2{Beam broken<br/>within the window?}
    W2 -->|yes| Stop
    W2 -->|no| P1

This is why a trial recorded as rewarded really was rewarded. A dispenser that turns by a fixed amount sometimes delivers nothing, because pellets jam, and the record would not show it. An animal that reaches the correct arm and receives nothing learns the wrong lesson.

firmware/arduino/testIR/testIR.ino prints all four detectors continuously, for checking the beams and their alignment. firmware/arduino/i2c_scanner/ confirms the PCA9685 is visible on the I2C bus.

Auditory maze: TTL synchronisation¶

firmware/ttl_bnc/TTL_bnc.ino listens on the serial port and drives one pin: H takes it high when a sound starts, L takes it low when the sound ends or the animal leaves the arm. Wire that pin to the digital input of the system you want to align to, such as a fibre photometry rig.

Only needed when something else must be aligned to the sound. Ordinary auditory sessions do not use it.

MicroPython¶

firmware/micropython/ holds the Adafruit PCA9685 driver for running the servos from a MicroPython board instead of an Arduino.

The BeeHive board¶

The tactile rig uses a BeeHive board developed at the University of Sussex alongside the Arduino and the PCA9685. Its documentation is not yet part of this repository; a description and a link should be added here.