MAD - Matrix Display

The MAD project is based on a pcb with an ATtiny406/ATtiny1606 and a Matrix LED Display. It can be used to display data sent over SPI or UART. The display also implements a small amount of characters from the ASCII table and also has internal space (EEPROM) for 16 special characters that can be programmed.

Experience	Level
Soldering
Mechanical
Software

Downloads

Type	File	Description
Schematic	pdf / cadlab	Schematic files
Board	pdf / cadlab	Board file
Drill	pdf	Drill file
Gerber	zip / tar	Gerber/Drill files
Housing, PCB	zip / tar	Housing and PCB (STEP) files
Firmware	zip / tar	Firmware for ATtiny406/ATtiny1606 (Display)
Firmware (demo)	zip / tar	Test application(s) for ATmega16a

Hardware

There are two parts of the hardware. The pcb and the housing of the MAD. The pcb is created with KiCAD and the housing with FreeCAD. The software is programmed with Microchip (Atmel) Studio. All files are built with github actions so that they are ready for a production environment. The housing is printed with a 3D-printer (Dremel 3D40).

PCB

The circuit board is populated on both sides (Top, Bottom). The best way for soldering the SMD components is within a vapor phase soldering system and for the THT components with a standard soldering system.

Top Layer

Bottom Layer

Mechanical

The housing has a tolerance of 0.2mm on each side of the case. So the pcb should fit perfectly in the housing. The tolerance can be modified with FreeCAD in the Parameter Spreadsheet.

Assembled

Exploded

Programming/Setup

The MAD is powerd with 5V from an external source. With Jumper JP1 bridged the MAD can be programmed over UPDI. To enable UART mode the SS (CS) Pin must be held low (more details on the dataflow diagram) otherwise the SPI mode is enabled. In UART mode only one display can be driven. The SI pin gets TXDand the SO pin gets RXD. The firmware for the display can be downloaded (see the download section).

FUSES

Register	Value
WDTCFG	0x00
BODCFG	0x00
OSCCFG	0x02
TCD0CFG	0x00
SYSCFG0	0xF5
SYSCFG1	0x00
APPEND	0x00
BOOTEND	0x00

To setup SW1 as RESET (PA0) it is necessary to change the SYSCFG0-FUSE of the ATtiny406/ATtiny1606. WARNING: To reset the PA0 pin to UPDI mode a 12V impulse is necessary to program the FUSES again.

Software

The display software can be controlled by SPI or UART. The interfaces are displayed in the dataflow diagram. There is a demo software to use the display directly over spi (MAD_Test) or a library (MAD_LIB).

Dataflow diagram

UART Test

To send characters to the display over UART connect an USB/UART converter to the PC and make a bridge beween GND and SS (CS) before powering up the display. Start a terminal software on the computer (e.g. Teraterm) and setup the following settings:

Name	Value
PORT	COM?
BAUD	9600
DATABITS	8
PARITY	NONE
STOPBITS	1
FLOWCTRL	NONE

Connection setup

#      +---------------------+                                +---------------------+
#      |    MAD - Display    |                                |                     |
#    +-+-+                 +-+-+                              | +-----------------+ |
#    | 1 | VCC         VCC | 1 +-------+    +----------+      | | TeraTerm        | |
#    | 2 | UPDI       UPDI | 2 |       |    |   U  +---+---+  | | ~~~~~~~~        | |
#    | 3 | SI           SO | 3 +-----+ |    |   S  |  USB  |--+ | ~~~~~           | |
#    | 4 | SCK         SCK | 4 |     | |    |   B  +---+---+  | | ~~~~~~~~~~~~    | |
#    | 5 | SS (CS)      SS | 5 +--+  | |    |   /      |      | |                 | |
# +--+ 6 | GND         GND | 6 +--+  | |    |   U      |      | +-----------------+ |
# |  +-+-+                 +-+-+     | |  +-+-+ A      |      |                     |
# |    +---------------------+       | +--+VCC| R      |      | Computer            |
# |                                  +----+TxD| T      |      |                     |
# |                                       |RxD| +------+      +---------------------+
# +---------------------------------------+GND| |5V/3V3|
#                                         +-+-+ +------+
#                                           +----+-----+

SPI Test

The firmware itself contains some demos how to use the display over spi. The demo software itself is written for an ATmega16A. To test the display a connection to the spi pins between the display and the ATmega16Ais necessary.

Connection setup

# ~------------+                  +---------------------+
# ~            |                  |     MAD - Display   |
# ~  A       +-+-+              +-+-+                 +-+-+
# ~  T   [7] | P +- SCK -+      | 1 | VCC         VCC | 1 |
# ~  M       | O |        \     | 2 | UPDI       UPDI | 2 |
# ~  E       | R +- MOSI --\----+ 3 | SI           SO | 3 |
# ~  G       | T +-- SS -+  +---+ 4 | SCK         SCK | 4 |
# ~  A       | B |       +------+ 5 | SS (CS)      SS | 5 |
# ~          |   |              | 6 | GND         GND | 6 |
# ~  1       |   |              +-+-+                 +-+-+
# ~  6   [0] |   |                |                     |
# ~  A       +-+-+                +---------------------+
# ~            |
# ~~~~~~~~~~~~~~ 

SPI Parameter

To control the display through SPI the bus of the master needs the following setup:

Parameter	Value	Description
Clock	< 1Mhz	Bus clock speed should not exceed this value
Direction	MSB	MSB needs to be transmitted first
Polarity	Rising	Polarity of clock is rising _/
Phase	Rising	Data is valid when clock is rising _/

Detail can be found here

SPI Frame

# SPI display transmission
# _                                                SS                                                _
#  \________________________________________________________________________________________________/
#                                                 SCK   
#     __    __    __    __    __    __    __    __    __    __    __    __    __    __    __    __    
# ___/1 \__/2 \__/3 \__/4 \__/5 \__/6 \__/7 \__/8 \__/9 \__/10\__/11\__/12\__/13\__/14\__/15\__/16\___
#                                                 MOSI
#    __    __    __    __    __    __    __    __    __    __    __    __    __    __    __    __
# __/C \__/T \__/R \__/L \__/B \__/Y \__/T \__/E \__/D \__/A \__/T \__/A \__/B \__/Y \__/T \__/E \____
#   \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/  \__/
#    [7                   :                    0]    [7                   :                    0]

SPI Commands

To enable a bit it needs to be set to on ($1=ON$). To disable a bit it is necessary to set it to off ($0=OFF$).

Control-Byte	Data-Bit(s)	Description
0x00	0xXX	No operation
0x01	[4:0]	ROW1 LEDs
...	...	...
0x07	[4:0]	ROW7 LEDs
0x08	[6:0]	Show ASCII character on display
0x10	0xXX	Clear buffer
0x1F	[0]	Enable display
0x20	0xXX	Copy EEPROM address (0) to display
...	...	...
0x2F	0xXX	Copy EEPROM address (15) to display
0x30	0xXX	Copy Display content to EEPROM address (0)
...	...	...
0x3F	0xXX	Copy Display content to EEPROM address (15)
0xF0	0xXX	Display refresh rate LOW byte
0xF1	0xXX	Display refresh rate HIGH byte
0xFF	0xXX	RESET the SPI queue

Example Library (matrix.h)

With the attached demo library (MAD_LIB) it is quiet easy to use the display. To setup the matrix display library some defines needs to be adjusted.

// Setup the number of displays that are cascaded
#ifndef MATRIX_DISPLAYS
    #define MATRIX_DISPLAYS 2
#endif

#include "../lib/matrix/matrix.h"

int main(void)
{
    matrix_init();
    matrix_reset();
    _delay_ms(MATRIX_RESET_RECOVERY_TIME_MS);
    matrix_enable();

    matrix_char(1, 'A');
    _delay_ms(1000);
    matrix_char(2, 'B');

    matrix_frame(buffer);
    // ...
}

Additional Information

Type	Link	Description
ATtiny406	pdf	ATtiny microcontroller
ATtiny1606	pdf	ATtiny microcontroller
ATmega16A	pdf	Microchip ATmega16A Datasheet
TA20-11SRWA	pdf	Dot Matrix Dispaly
Atmel ICE	pdf	Atmel ICE datasheet
UPDI	web	UPDI-Adapter with AVR-Dude
Microchip Studio	web	Download page for Microchip Studio
KiCAD	web	KiCAD project page
FreeCAD	web	FreeCAD project page
TeraTerm	web	Terminal software for UART

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R. GAECHTER