'--------------------------------------------------------------------------------
'name : BG30dB_LED.bas
'copyright : (c) 1995-2016, MCS Electronics
'purpose : create a logarithmic LED bar graph dB (VU) meter
'micro : Attiny2313
'suited for demo : yes
'commercial addon needed : no
'use in simulator : possible
'
' Author : Ger langezaal
'
'---[ Small program description ]-----------------------------------------------
'
' This program is written to create a logarithmic LED bar graph dB (VU) meter
' with peak-hold and drop-down. Scale range is 30dB in 3dB steps.
' Log conversion is done with the analog comparator on a RC discharge curve.
' C1 is charged each 4mS with PB0 as output on a Timer0 Interrupt.
' Then PB0 is set to AIN0 (analog comparator +input) Timer1 is reset
' and start counting, C1 will be discharged by R1.
' Timer1 is counting until AIN0 < AIN1.
' Analog Comparator Output = ACSR bit 5.
' Timer1 value is in T1 stored for calculation.
'
' Display mode is set with PD6 (pin 11).
' 1 = bar mode
' 0 = dot mode (for low current applications)
'---[ LED to AVR connections ]--------------------------------------------------
'
' AVR Resistor Cathode dB
' Port pin Ohm LED nr Scale
' PD5 9 >--[680]--> 11 +6
' PD4 8 >--[680]--> 10 +3
' PD3 7 >--[680]--> 9 0
' PD2 6 >--[680]--> 8 -3
' PD1 3 >--[680]--> 7 -6
' PD0 2 >--[680]--> 6 -9
' PB7 19 >--[680]--> 5 -12
' PB6 18 >--[680]--> 4 -15
' PB5 17 >--[680]--> 3 -18
' PB4 16 >--[680]--> 2 -21
' PB3 15 >--[680]--> 1 -24
' PB2 14 >--[680]--> 0 infinit
'
' All LED Anodes to +5 Volt
'
'---[ Analog comparator inputs ]------------------------------------------------
'
'
' Meter DC input >-------[ R2 ]-------> PB1 (AIN1 pin 13)
' |
' GND <---------||-----
' C2
'
' ---[ R1 ]---
' GND <----| |----> PB0 (AIN0 pin 12)
' -----||-----
' C1
' R1 = 10k 5%
' R2 = 10k
' C1 = 47nF 5%
' C2 = 47nF
'
'---[ DC input versus Timer1 and Led position ]---------------------------------
'
' Measured Timer1 values for calculation:
' DC input = 3500mV Timer1 = 192 ( +6dB)
' DC input = 312mV Timer1 = 1544 (-15dB) 21dB = factor 11.22
' 21dB = 1543 - 192 = 1351 Timer1 counts
' 3dB = 1351 / 7 = 193 Timer1 counts
'
' Input mv Timer1 LED pos dB scale
' 3500 192 11 +6
' 2477 385 10 +3
' 1753 578 9 0
' 1241 771 8 -3
' 879 965 7 -6
' 622 1158 6 -9
' 440 1351 5 -12
' 312 1544 4 -15
' 220 1737 3 -18
' 156 1930 2 -21
' 110 2123 1 -24
' <110 >2123 0 infinit
'
'---[ Compiler and hardware related statements ]--------------------------------
$regfile = "attiny2313.dat" 'register file for Attiny2313
$crystal = 10000000 '10MHz crystal
$hwstack = 32 ' default use 32 for the hardware stack
$swstack = 10 'default use 10 for the SW stack
$framesize = 40 'default use 40 for the frame space
Ddrb = &B11111100 'PB0 and PB1 are analog inputs
Portb.0 = 0 'disable input pullup
Portb.1 = 0 'disable input pullup
Ddrd = &B10111111 'config PD6 as input
Portd = &B11111111 'output high and enable input pullup
Acsr.7 = 0 'enable analog comparator ACSR bit 7 = 0
'---[ Variables ]---------------------------------------------------------------
Dim Peak_pos As Byte
Dim Peak_hold As Byte
Dim Drop_hold As Byte
Dim Led_pos As Word
Dim Bar_pattern As Word
Dim T1 As Word
'---[ Constants ]---------------------------------------------------------------
Const Peak_hold_time = 200
Const Drop_down_time = 40
Const Led_max = 11 'Led 0 - 11
Const T1_fs = 192 'full scale Timer1 value
Const T1_step = 193 '3dB step Timer1 value
Const T1_range = T1_step * Led_max + T1_fs 'Calculate Timer1 range
Displ_mod Alias Pind.6 'display mode 1 = Dot 0 = Bar
Ac_out Alias Acsr.5 'analog comparator output = ACSR bit 5
'---[ Timer Configuration ]-----------------------------------------------------
Config Timer0 = Timer , Prescale = 256 'On Interrupt Timer
Config Timer1 = Timer , Prescale = 8 'R/C Timer
Config Watchdog = 1024 'reset after 1 Sec no reset watchdog
Enable Interrupts
Enable Timer0
Enable Timer1
On Timer0 Dc_input_sample 'on overflow timer0 jump to label
Timer0 = 0
Timer1 = 0
Start Timer0
Start Timer1
'---[ Main program loop ]-------------------------------------------------------
Do
Bar_pattern = &HFFFF 'set all bits
If Displ_mod = 1 Then 'bar display mode
Bar_pattern = Lookup(led_pos , Bar_mode)
Else 'dot display mode
Bar_pattern.led_pos = 0 'reset dot bit
End If
Bar_pattern.peak_pos = 0 'reset peak bit
Portd.5 = Bar_pattern.11 'led 11 = bit 11
Portd.4 = Bar_pattern.10
Portd.3 = Bar_pattern.9
Portd.2 = Bar_pattern.8
Portd.1 = Bar_pattern.7
Portd.0 = Bar_pattern.6
Portb.7 = Bar_pattern.5
Portb.6 = Bar_pattern.4
Portb.5 = Bar_pattern.3
Portb.4 = Bar_pattern.2
Portb.3 = Bar_pattern.1
Portb.2 = Bar_pattern.0 'led 0 = bit 0
Loop
'-------------------------------------------------------------------------------
End
'-------------------------------------------------------------------------------
'---[ Interrupt Service Routine on Timer0 overflow ]---------------------------
Dc_input_sample:
Timer0 = 100 'preset Timer0 for sample rate of 4mS
Ddrb.0 = 1 'set AIN0 as PB0 output
Portb.0 = 1 'set PB0 high to charge C1
Waitus 200 'wait for charge complete
Ddrb.0 = 0 'reset PB0 as AIN0 analog input
Portb.0 = 0 'disable AIN0 pullup
Timer1 = 0 'clear R/C Timer1
Bitwait Ac_out , Reset 'wait for AIN0 < AIN1
T1 = Timer1 'read Timer1 value
If T1 < T1_fs Then 'check T1 low limit
T1 = T1_fs 'T1 clipping
Elseif T1 > T1_range Then 'check T1 high limit
T1 = T1_range 'T1 clipping
End If
Led_pos = T1_range - T1 'calculate led position
Led_pos = Led_pos \ T1_step 'led_pos = 0 - 11
If Led_pos >= Peak_pos Then 'new peak value
Peak_pos = Led_pos 'store peak value
Peak_hold = Peak_hold_time 'preset peak hold timer
Else
If Peak_hold > 0 Then
Decr Peak_hold
Else
If Drop_hold > 0 Then
Decr Drop_hold
Else
Drop_hold = Drop_down_time 'preset drop down timer
If Peak_pos > 0 Then Decr Peak_pos 'drop down one position
End If
End If
End If
Reset Watchdog
Return
'---[ Led Bar pattern lookup data ]---------------------------------------------
' Led 11......... 0
Bar_mode:
Data &B1111111111111110% 'Word constants must end with the %-sign
Data &B1111111111111100%
Data &B1111111111111000%
Data &B1111111111110000%
Data &B1111111111100000%
Data &B1111111111000000%
Data &B1111111110000000%
Data &B1111111100000000%
Data &B1111111000000000%
Data &B1111110000000000%
Data &B1111100000000000%
Data &B1111000000000000%
'-------------------------------------------------------------------------------