Fab - Phil Learns How to Make

Embedded Programming

Program a Micro-Controller.

The goal this week is to bring intelligence to the circuit board. To do that, we connect the microcontroller we milled and soldered in week 6 to the AVR programmer we created in week3.

Setting Up

It's important to verify that both the FabISP programmer and FTDI Cable are being recognized by the computer

Key Commands

1. Convert C code into Hex: sudo make program-usbtiny

2. Prepare the programmer to write: make -f Makefile program-usbtiny-fuses

3. Write the Hex to the microcontroller: make -f Makefile program-usbtiny

4. Unplug the programmer from the microcontoller

5. Look up serial port number: ls /dev/tty*

dhcp-18-111-2-197:ep-hello ptinn$ ls /dev/tty*
                            /dev/tty        /dev/ttysd
                            /dev/tty.Bluetooth-Incoming-Port  /dev/ttyse
                            /dev/tty.Bluetooth-Modem    /dev/ttysf
                            /dev/tty.iPad-WirelessiAP   /dev/ttyt0
                            /dev/tty.usbserial-FTHBSO75   /dev/ttyt1
                            /dev/ttyp0        /dev/ttyt2
                            /dev/ttyp1        /dev/ttyt3
                            /dev/ttyp2        /dev/ttyt4

6. Run ahello world: python term.py /dev/tty.usbserial-FTHBSO75 115200

dhcp-18-111-2-197:ep-hello ptinn$ python term.py /dev/tty.usbserial-FTHBSO75 115200
                                                        Nov  4 10:28:14 dhcp-18-111-2-197.dyn.mit.edu Python[6509] <Error>: The function ‘CGContextErase’ is obsolete and will be removed in an upcoming update. Unfortunately, this application, or a library it uses, is using this obsolete function, and is thereby contributing to an overall degradation of system performance.
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 587, in callit
                                                            func(*args)
                                                          File "term.py", line 45, in idle
                                                            wait = ser.inWaiting()
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/serial/serialposix.py", line 449, in inWaiting
                                                            s = fcntl.ioctl(self.fd, TIOCINQ, TIOCM_zero_str)
                                                        IOError: [Errno 6] Device not configured
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "term.py", line 31, in key
                                                            if (ord(key) == 13):
                                                        TypeError: ord() expected a character, but string of length 0 found
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "term.py", line 31, in key
                                                            if (ord(key) == 13):
                                                        TypeError: ord() expected a character, but string of length 0 found
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "term.py", line 31, in key
                                                            if (ord(key) == 13):
                                                        TypeError: ord() expected a character, but string of length 0 found
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "term.py", line 31, in key
                                                            if (ord(key) == 13):
                                                        TypeError: ord() expected a character, but string of length 0 found
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "term.py", line 31, in key
                                                            if (ord(key) == 13):
                                                        TypeError: ord() expected a character, but string of length 0 found
                                                        Exception in Tkinter callback
                                                        Traceback (most recent call last):
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-tk/Tkinter.py", line 1536, in __call__
                                                            return self.func(*args)
                                                          File "term.py", line 33, in key
                                                            ser.write(key)
                                                          File "/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/serial/serialposix.py", line 518, in write
                                                            raise SerialException('write failed: %s' % (v,))
                                                        SerialException: write failed: [Errno 6] Device not configured

Code blocks generated using: http://hilite.me/

Output

Make the microcontroller do something.

Where microcontroller pins are decleared to give LED instructions to light on/off. Pay special attention to the selection of Clock Prescaler

#include <avr/io.h>
                                #include <util/delay.h>

                                #define output(directions,pin) (directions |= pin) // set port direction for output
                                #define set(port,pin) (port |= pin) // set port pin
                                #define clear(port,pin) (port &= (~pin)) // clear port pin
                                #define pin_test(pins,pin) (pins & pin) // test for port pin
                                #define bit_test(byte,bit) (byte & (1 << bit)) // test for bit set
                                #define PWM_delay() _delay_us(25) // PWM delay

                                #define led_port PORTB
                                #define led_direction DDRB
                                #define red (1 << PB1)
                                #define green (1 << PB0)
                                #define blue (1 << PB2)

                                int main(void) {
                                   //
                                   // main
                                   //
                                   unsigned char count, pwm;
                                   //
                                   // set clock divider to /1
                                   //
                                   CLKPR = (1 << CLKPCE);
                                   CLKPR = (0 << CLKPS3) | (0 << CLKPS2) | (0 << CLKPS1) | (0 << CLKPS0);
                                   //
                                   // initialize LED pins
                                   //
                                   set(led_port, red);
                                   output(led_direction, red);
                                   set(led_port, green);
                                   output(led_direction, green);
                                   set(led_port, blue);
                                   output(led_direction, blue);
                                   //
                                   // main loop
                                   //

To understand the code, it is necessary to refer to the following diagrams from the datasheet of Attiny45 datasheet:

DDRB: Data Directory Registry Port
MOSI: SPI Master Data Output / Slave Data Input
MISO: SPI Master Data Input / Slave Data Output
XTAL1: Crystal Oscillator Input
XTAL2: Crystal Oscillator Output

CLKPR – Clock Prescale Register

Bit 7 – CLKPCE: Clock Prescaler Change Enable
Bits 3:0 – CLKPS[3:0]: Clock Prescaler Select Bits 3 - 0

According to the Data-sheet:
To avoid unintentional changes of clock frequency, a special write procedure must be followed to change the CLKPS bits:

Write the Clock Prescaler Change Enable (CLKPCE) bit to one and all other bits in CLKPR to zero.
2Within four cycles, write the desired value to CLKPS while writing a zero to CLKPCE.

Makefile: hello.RGB.45.make

PROJECT=hello.RGB.45
                                                SOURCES=$(PROJECT).c
                                                MMCU=attiny45
                                                F_CPU = 8000000

                                                CFLAGS=-mmcu=$(MMCU) -Wall -Os -DF_CPU=$(F_CPU)

                                                $(PROJECT).hex: $(PROJECT).out
                                                    avr-objcopy -O ihex $(PROJECT).out $(PROJECT).c.hex;\
                                                    avr-size --mcu=$(MMCU) --format=avr $(PROJECT).out
                                                 
                                                $(PROJECT).out: $(SOURCES)
                                                    avr-gcc $(CFLAGS) -I./ -o $(PROJECT).out $(SOURCES)
                                                 
                                                program-bsd: $(PROJECT).hex
                                                    avrdude -p t45 -c bsd -U flash:w:$(PROJECT).c.hex

                                                program-dasa: $(PROJECT).hex
                                                    avrdude -p t45 -P /dev/ttyUSB0 -c dasa -U flash:w:$(PROJECT).c.hex

                                                program-avrisp2: $(PROJECT).hex
                                                    avrdude -p t45 -P usb -c avrisp2 -U flash:w:$(PROJECT).c.hex

                                                program-usbtiny: $(PROJECT).hex
                                                    avrdude -p t45 -P usb -c usbtiny -U flash:w:$(PROJECT).c.hex

                                                program-dragon: $(PROJECT).hex
                                                    avrdude -p t45 -P usb -c dragon_isp -U flash:w:$(PROJECT).c.hex

Final Project: Electric Tambourine (W.I.P.)

Enhancing the Percussion User Interface of Open-Source MIDI Controller.

This project is inspired by the Sugarcube-MIDI project created by Amanda Ghassaei for Instructable. Here I try to focus refining the form factor of the device as a handheld instrument. The intention is to improve the percussion quality of the device by fully utilize a 9-degree-of-freedom sensor (accelerometer, gyroscope and magnetometer

This page documents the issues and progress made so far during the investigation.

UX Study

I start by examining the gripping experience of electronic objects found in the lab. Handles come in different sizes: the handle of OLPC (~2cm) is designed primarily for carrying, while handle of Sense 3D scanner (~3.5cm) is more suitable for stable handling and movement control.

Control Interface Study

In a typical MIDI-Controller, analog potentiometers are used for adjusting tempo, and sound velocity. They can also be used to provide more funcitonal assignments beyond the number of buttons in the grid (4x4). Here I imagine the use case where one wants to control the instrument with only one hand while using the other hand for other pursposes. Here, we disover the need to create spaces inside the handle to house the potentiometers.

3D Modeling and Production

Based on the usability and scale/dimensional requirement collected from previous two steps, I move on to building a 3D model using Rhino.

Electronics

The electric tambourine is made up of multiple electronic components, including pre-fabricated 4x4 silicon button pad for LED, breakout board, and 9-DOF position sensor. During the integration process, I went through a few sources on the following: