Up to Laser_PC_Board_Designs

Firmware for Rev 2 Laser/TEC system

I2C Bus

Four-channel I2C DAC ​LTC2635 Address as follows by crate slot:

  Slot  I2C   Note
  000   0x20  Slot 0 - default
  001   0x24  Slot 1
  010   0x44  Slot 2
  011   0x60  Slot 3
  100   0xa4  Slot 4
  101   0xc0  Slot 5

I2C bus is common to all uC (and to backplane if R5, R6 on Laser/TEC board installed).

uC Pinout

uC on Laser/TEC is ​ATMEGA164A

ADC reference should be external (REFS1=REFS0=0)

'Pin	Func	Name	Note
PA0/ADC0	ADC	ISENSE	Current sense 0.5V = 1A (4.88mA/LSB)
PA1/ADC1	ADC	THERM_LASER	Laser temperature ADC input (512 @ 25 deg C)
PA2/ADC2	ADC	THERM_HOT	TEC hot side ADC input (512 at 25 deg C)
PA3/ADC3	ADC	FAN_STATUS	Pulse if fan running
PA4/ADC4	ADC	QTEMP	Current source transistor temperature ADC input (512 at 25 deg C)
PA5/ADC5		n.c.
PA6/ADC6	IN	TEMP_FAIL	Over-temperature (logic 1' if temp outside window) (Note 1)
PA7/ADC7	IN	OVER_CURRENT	Over-current (logic 1' if over current set by pot)

Note 1 - Window set by R105,R107,R108 (3 per channel). Default values give 2.5V +/- 0.5V. 'Resistors R105 etc must be changed to 30k

'Pin	Func	Name	Note
PB0-PB1	IN	CH_ADR0-1	Channel address 0-3
PB2-PB4	IN	SL_ADR0-2	Slot address 0-7
PB5-PB7	IN	not used	programming connector
'Pin	Func	Name	Note
PC0-PC11	I2C	I2C SCL/SDA	disable except on channel 0?
PC2	OUT	LED D1	0' for on, uC status
PC3	OUT	LED D5	1' for on, laser on
PC4-PC7		n.c.
'Pin	Func	Name	Note
PD0/RXD0	UART	RS-485 Rx	RS-485 receive data
PD1/TXD0	UART	RS-485 Tx	RS-485 transmit data
PD2-PD3	IN	FAULT0-1	Fault input for TEC PWM (Note 2)
PD4	OUT	PWM-	TEC PWM output (Note 3)
PD5	OUT	PWM+	TEC PWM output
PD6	OUT	DE	RS-485 driver enable
PD7	OUT	L_SHDN	Laser shutdown. Logic 1' to disable laser

Note 2: PWM condtions: "00"-Overcurrent, "01"-Undervoltage, "10"-Overtemperature, "11"-Normal

Note 3: Assuming TEC is wired with "+ lead to J20 pin 1, PWM+ provides cooling with PWM-='0'. PWM- provides heating with PWM+='0'