Firmware for a Deal Extreme “JY-MCU 3208 Lattice Clock”.

Schematics found at http://fw.hardijzer.nl/?p=148 (as of 2012-12-30).

Components used on this particular board are:

 • 4 8x8 LED matrices
 • Holtek HT1632C LED Matrix Controller
 • AVR AT-Mega8 MCU (8k flash, 1k RAM, 512b EEPROM)

Optionally, there is place for

 • RX-8025NB, RX8025SA or DS1302 RTC
 • Buzzer (Port PC0)
 • IR Receiver (?)
 • 1 Wire Thermometer (DS18B20)

Mega8 Ports and Pins

	Port	Alternate Fct.	Schematic Name	Description
	-------:---------------:---------------:------------------------------
	ADC6	-		-		(unused)
	ADC7	-				(unused)
	PB0	ICP1		SCL_INTA	to RTCs
	PB1	OC1A		I/O_SCL		to RTCs
	PB2	OC1B		RST_SDA		to RTCs
	PB3	MOSI		\CS, MOSI	HT1632C \CS and ISP conn.
	PB4	MISO		\WR, MISO	HT1632C \WR and ISP conn.
	PB5	SCK		DATA, SCK	HT1632C DATA and ISP conn.
	PB6	XTAL1		-		32k768 Xtal
	PB7	XTAL2		-		32k768 Xtal
	PC0	ADC0		PC0		Buzzer
	PC1	ADC1		-		2/5 of Vcc (15k/10k divider)
	PC2	ADC2		DQ		1Wire (18B20)
	PC3	ADC3		INTB		to RTCs
	PC4	ADC4/SDA	PC4		LED1 (A, via 2.2 kOhm)
	PC5	ADC5/SCL	PC5		LED1 (K)
	PC6	RST		RST		ISP conn, 100k Pullup
	PD0	RxD		RxD		ISP conn (serial port)
	PD1	TxD		TxD		ISP conn
	PD2	INT0		D+		USB Connector via R.
	PD3	INT1		INT1		IR Receiver, Pin1
	PD4	XCK/T0		D-		USB Connector via R
	PD5	T1		KEY3		Button to GND
	PD6	AIN0		KEY2		Button to GND
	PD7	AIN1		KEY1		Button to GND
	-------:---------------:---------------:------------------------------

ISP + Serial Port Connector

	.................................
                                        :
	-------+         +------------+ :
	       |         | POWER_CONN | :
	       |         +------------+ :
	       |                        :
	       | GND     10 --o o-- 9 PB4/MISO
	Matrix | PD0/RxD  8 --o o-- 7 PB5/SCK
	       | PD1/TxD  6 --o o-- 5 PC6/RST
	       | GND      4 --o o-- 3 n/c
	-------+ Vcc      2 --o o-- 1 PB3/MOSI
	                                :
	................................:

FUSE Settings

	hfuse	0xc9	(def: 0x99)
		-> disabled watchdog, enabled CKOPT fuse (for clock selection)

	lfuse	0xe4	(def: c1)
		-> 8 MHz internal clock


	lock	0x3f

LED Matrix Connection

The LED matrix is connected in a 32x8 fashion to the MCU, the correct configuration
to be stored in the HT1632C is n-channel outputs and 8 common drivers.

Addressing is by 4bit groups (nibbles) with the MSB being the leftmost pixel
of each group.

┌─────────────────────────────────────────┬─────┐
│ 00__ 01__ 16__ 17__ 32__ 33__ 48__ 49__ │ PWR>│
│ 02__ 03__       :         :         :   │     │
│ 04__ 05__   :        :         :        │     │
│ 06__ 07__       :         :         :   │ ┌─┐ │
│ 08__ 09__   :        :         :        │ │PR │
│ 10__ 11__       :         :         :   │ │OG │
│ 12__ 13__   :        :         :        │ └─┘ │
│ 14__ 15__ 30__ 31__ 46__ 47__ 62__ 63__ │     │
└─────────────────────────────────────────┴─────┘
  <───────> <───────>  <───────> <───────>
  1st Matrix 2nd        3rd       4th

  00__ are the left upmost pixels, with bits allocated MSB first.