PiSteer

Autosteer controller.

Warning

This just just for demonstration and proof of concept. This should never ever be used on full sized machinery. You will crash and die if You do. You have been warned.

Other documents

Pictures and something here.

Raspberry Pi 3

Why Raspberry Pi? It's just somethin I had laying around.

Install

From fresh Raspberry PI OS.

sudo apt-get update
sudo apt-get upgrade
sudo apt-get install pip
pip install smbus2
pip install pyserial

Configure raspberry:

sudo raspi-config

From System Options set Wireless LAN, from Interface Options enable I2C, disable login console on serial port, enable serial port hardware.

Edit /boot/config.txt

sudo nano /boot/config.txt

Add the line dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4 Save the file and reboot.

Run program

Run program by:

python pi-steer/autosteer.py

To start automatically at boot enter crontab -e and add following line.

@reboot python /home/pi/pi-steer/autosteer.py & > /dev/null 2>&1

sudo crontab -e @reboot /bin/sleep 5; /usr/bin/python /home/pi/pi-steer/autosteer.py &

Raspberry Pi pinout

Device	pin	Pi GPIO	Pi pin	Pi pin	Pi GPIO	pin	Device
BSS138, BNO055, BNO085 VCC/PS0	LV, VIN	3v3 Power	1	2	5V Power	HV, VDD	BSS138, ADS1115
BSS138 (ADS1115), BNO055	A2, SDA	I2C SDA	3	4	5V Power	VCC, 1-A	RTY120LVNAA
BSS138 (ADS1115), BNO055	A1, SCL	I2C SCL	5	6	Ground	GND, 2-B	RTY120LVNAA
Relay, up/down	up	GPIO 4	7	8	GPIO 14	TXD	BNO085 SCL/SCK/RX
BNO055	GND	Ground	9	10	GPIO 15	RXD	BNO085 S/MISO/TX
Relay, up/down	down	GPIO 17	11	12	GPIO 18	16	Relay
Autosteer switch	A	GPIO 27	13	14	Ground	GND	Relay
Relay	1	GPIO 22	15	16	GPIO 23	15	Relay
LED:s	+	3v3 Power	17	18	GPIO 24	14	Relay
Relay	2	GPIO 10	19	20	Ground	-	Power LED
Relay	3	GPIO 9	21	22	GPIO 25	13	Relay
Relay	4	GPIO 11	23	24	GPIO 8	12	Relay
Autosteer switch	B	Ground	25	26	GPIO 7	11	Relay
Relay	5	GPIO 0	27	28	GPIO 1	10	Relay
Relay	6	GPIO 5	29	30	Ground	GND	BSS138
Relay	7	GPIO 6	31	32	GPIO 12, PWM 0	PWM	Cytron
Work switch		GPIO 13	33	34	Ground	GND	Cytron
Relay normal mode, switch	2	GPIO 19	35	36	GPIO 16	DIR	Cytron
Relay up/down mode, switch	1	GPIO 26	37	38	GPIO 20	9	Relay
Relay mode switch	GND	Ground	39	40	GPIO 21	8	Relay

Wheel angle sensor RTY120LVNAA

Function	pin
Vcc 5V	1-A
GND	2-B
output	3-C

Adafruit ADS1115 4-Channel ADC and 4-channel I2C-safe Bi-directional Logic Level Converter - BSS138

Wires connectedd to raspberry Pi via level converter

GPIO	Pi pin number	BSS138
3v3 Power	1	LV
5V Power	2	HV
I2C1 SDA	3	A1
I2C1 SCL	5	A2
Ground	7	GND

GPIO	Pi pin number	ADS1115	BSS138	RTY120LVNAA
5V Power	4		VIN	1-A
		SDA	B1
		SCL	B2
Ground	20	GND	GND	2-B
		A0		3-C

Inertial masurement unit (IMU)

BNO055 and BNO085 are supported. Software detects and selects witch ever is connected. BNO085 is supposed to be better than BNO055. The problem is that at the moment as I am writing this BNO085 is almost impossible to found anywhere.

I have used both at 2020. Earlier I used Adafruit libraries for both.

BNO055 was mostly unusable. roll was drifting very bad and heading was jumping randomly. I have written more direct messaging based on datasheet. There are still some errors which are taken care of. Roll is OK, heading drifts slightly on moving tractor. It's not good but it is usable, at least on higher GPS heading usage.

The problem with BNO085 is that I2C communication is more complicated to write and I2C (at least Adafruit I2C library) is very unstable, it crashes often. Luckily there is more simple solution. When PC0 pin set high, xxxx-RCV mode is activated and BNO085 sends easy to use data at 100 Hz rate. And it seems to be stable.

BNO055

BNO055 is connected by I2C.

Wires connectedd to raspberry Pi.

GPIO	Pi pin number	BNO085
3v3 Power	1	VIN
I2C1 SDA	3	SDA
I2C1 SCL	5	SCL
Ground	9	GND

https://github.com/adafruit/Adafruit_BNO055

https://www.bosch-sensortec.com/media/boschsensortec/downloads/datasheets/bst-bno055-ds000.pdf

https://en.wikipedia.org/wiki/Conversion_between_quaternions_and_Euler_angles

BNO085

BNO085 is connected by serial. It uses xxxx-RCV mode.

Wires connectedd to raspberry Pi.

GPIO	Pi pin number	BNO085
3v3 Power	1	VIN
I2C1 SDA	XX	SDA
I2C1 SCL	XX	SCL
Ground	9	GND
PC0	9	GND

https://learn.adafruit.com/adafruit-9-dof-orientation-imu-fusion-breakout-bno085

https://www.ceva-dsp.com/wp-content/uploads/2019/10/BNO080_085-Datasheet.pdf

Motor controller Cytron MD13S

https://docs.google.com/document/d/1icu1GVDxZhUn3ADSUc3JknNcmUMdPcsnJ4MhxOPRo-I/view

Set hardware PWM on Raspberry Pi 3 https://blog.oddbit.com/post/2017-09-26-some-notes-on-pwm-on-the-raspb/

Now it is not fully hardware PWM. I think it uses DMA and maybe kernel code to maintain PWM, 20 kHz uses uses about 100 % of CPU. 2 kHz is used is this code. It is still a lot better than gpiozero fully software PWM, where maximum practical frequency is around 300 Hz.

edit /boot/config.txt Add the line dtoverlay=pwm-2chan,pin=12,func=4,pin2=13,func2=4 Save the file and reboot.

Motor controller wiring

GPIO	Pi pin number	Cytron
Ground	6	GND
GPIO 12, PWM0	32	PWM
GPIO 25	22	DIR

Autosteer switch

A microswitch to activate autosteer is connected to Raspberry Pi:

GPIO	Pi pin number	switch
Ground	30	A
GPIO 27	13	B

Status LEDs

Leds are connected between 3.3 V power (pin 17) and control pins

GPIO	Pi pin number	description
GPIO 22	15	Autosteer activated
GPIO 8	24	Motor direction
GPIO 23	16	Program activity
Ground	20	Power on

Relays

Pololu Basic 2-Channel SPDT Relay Carrier with 12VDC Relays https://www.pololu.com/product/2485

GPIO	Pi pin number	relay	12V	Output
GND	14	GND
		GND	GND	Out GND
		VDD	+12 V
GPIO 4	7	EN1
GPIO 17	11	EN2
		NO1		Output Up
		NO2		Output Down

Section control

Not implemented, sorry.

Tools

Some Python tools.

sniff-aog.py

Tool to read AgOpenGPS UDP data.

test_ads1115.py

Tool to test ADS1115 ADC.

test_bno085.py

Tool to test BNO085 IMU.

test_cytron_pwm.py

Test Cytron PWM motor controller (and motor).