2.5. Analogue tutorial
Let’s try some analogue features
2.5.1. analogue signal
An analogue signal varies between two limits corresponding to the supply \(V_{DDA}\) and \(V_{SSA}\).
At the exception of very specific design, most analogue signals are stepwise variation (switched-caps circuits, trimming operations, …). Therefore, only the final value change with a transition either corresponding to the charge (resp. discharge) of a capacitor, or linearly due to current limitation (slewing).
The analogue bricks corresponding to such behavior are c for capacitive
loading, and s for slewing. They accept a single value being either a number
or an expression depending on \(V_{DDA}\).
For more arbitrary functions, or continuous time functions, the analogue brick to
be used is a and accepts an array of numbers or an expression resulting into
an array of numbers.
set the content of the file to
{signal: [
{name: "gbf", wave: "0ssssccca...msMs", analogue: [
"0.5*VDDA", "0.6*VDDA", "0.7*VDDA", "0.9*VDDA", // first 4 's'
"0.2*VDDA", "0.8*VDDA", "0.3*VDDA", // 3 'c'
"[(t, (VDDA+VSSA)*(1 + sin(2*pi*t*3.5/Tmax))/2) for t in time]", // for 'a'
"0.25*VDDA", // for last s
"VDDA"
]}
]}
then generate an image with undulate
undulate -f svg -i step_1_ana.json -o step_1_ana.svg
set the content of the file to
gbf:
wave: "0ssssccca...msMs"
analogue:
- "0.5*VDDA" # first 4 's'
- "0.6*VDDA"
- "0.7*VDDA"
- "0.9*VDDA"
- "0.2*VDDA" # 3 'c'
- "0.8*VDDA"
- "0.3*VDDA"
- "[(t, (VDDA+VSSA)*(1 + sin(2*pi*t*3.5/Tmax))/2) for t in time]" # for 'a'
- "0.25*VDDA" # for last s
- "VDDA"
then generate an image with undulate
undulate -f svg -i step_1_ana.yaml -o step_1_ana.svg
set the content of the file to
gbf.wave = "0ssssccca...msMs"
gbf.analogue = [
"0.5*VDDA", # first 4 's'
"0.6*VDDA",
"0.7*VDDA",
"0.9*VDDA",
"0.2*VDDA", # 3 'c'
"0.8*VDDA",
"0.3*VDDA",
"[(t, (VDDA+VSSA)*(1 + sin(2*pi*t*3.5/Tmax))/2) for t in time]", # for 'a'
"0.25*VDDA", # for last s
"VDDA"
]
then generate an image with undulate
undulate -f svg -i step_1_ana.toml -o step_1_ana.svg
Note
Predefined constant and functions are provided in this analogue context. The exhaustive list of those is presented in section 2.3.
2.5.2. Superposition and style overloading
Mixed signal design shall have clear interface definition between analogue and digital. A common situation is a comparator giving a digital output of the comparison of two analogue signals.
In order to better convey the relation between the two analogue signals at the input of the comparator, it is interesting to superpose them with a different color.
Undulate allows a superposition of up to 4 signals. For that, the attribute
overlay should be set to True for the first 3 signals. Both signal and
signal’s name are superposed.
In order to clarify which signal is which, the position of the signal’s name
could be adjusted: the attribute order accepts a value between 0 and 4:
0: middle (default value)
1: top
2: middle-high
3: middle-low
4: bottom
set the content of the file to
{signal: [
{name: "mcu_clk", wave: "P", repeat: 10},
{name: "dac", wave: "c", repeat: 10, slewing: 32, vscale: 4, overlay: true,
stroke: [0, 0, 255, 255],
"stroke-dasharray": [1, 3],
fill: [0, 0, 255, 255],
"font-size": "9pt", order: 2, analogue: [
"VDDA*512/1024",
"VDDA*256/1024",
"VDDA*384/1024",
"VDDA*320/1024",
"VDDA*352/1024",
"VDDA*336/1024",
"VDDA*344/1024",
"VDDA*340/1024",
"VDDA*342/1024",
"VDDA*341/1024"
]},
{name: "vin", wave: "0a........", vscale: 4, overlay: true,
stroke: "#F00",
"stroke-dasharray": [5, 3, 1, 5],
"stroke-width": 1.5,
fill: "rgb(255, 0, 0)",
"font-size": "0.4em", order: 3, analogue: ["[(t, (VDDA/3)*(1-exp(-t/3))) for t in time]"]},
{name: "vmax", wave: "1.........", vscale: 4, order: 1, overlay: true},
{name: "vmin", wave: "l.........", vscale: 4, order: 4},
{name: "dac_ref", wave: "s", repeat: 10, slewing: 32, vscale: 4,
stroke: "#0000FFAA",
"stroke-dasharray": [1, 3],
fill: "#0000FF", order: 2, analogue: [
"VDDA*512/1024",
"VDDA*256/1024",
"VDDA*384/1024",
"VDDA*320/1024",
"VDDA*352/1024",
"VDDA*336/1024",
"VDDA*344/1024",
"VDDA*340/1024",
"VDDA*342/1024",
"VDDA*341/1024"
]}
]}
then generate an image with undulate
undulate -f svg -i step_2_ana.json -o step_2_ana.svg
set the content of the file to
# testcase to demonstrate the possibility
# of overlaying several curves
mcu_clk:
wave: "P"
repeat: 10
# value of the 10-bits DAC of a SAR
dac:
wave: "c"
repeat: 10
slewing: 32
vscale: 4
overlay: true
stroke: [0, 0, 255, 255]
stroke-dasharray: [1, 3]
fill: [0, 0, 255, 255]
font-size: "9pt"
order: 2
analogue:
- "VDDA*512/1024"
- "VDDA*256/1024"
- "VDDA*384/1024"
- "VDDA*320/1024"
- "VDDA*352/1024"
- "VDDA*336/1024"
- "VDDA*344/1024"
- "VDDA*340/1024"
- "VDDA*342/1024"
- "VDDA*341/1024"
# input voltage to which compare
vin:
wave: "0a........"
vscale: 4
overlay: true
stroke: "#F00"
stroke-dasharray: [5, 3, 1, 5]
stroke-width: 1.5
fill: "rgb(255, 0, 0)"
font-size: "0.4em"
order: 3
analogue:
- "[(t, (VDDA/3)*(1-exp(-t/3))) for t in time]"
# vmax
vmax:
wave: "1........."
vscale: 4
order: 1
overlay: true
# vmin
vmin:
wave: "l........."
vscale: 4
order: 4
dac_ref:
wave: "s"
repeat: 10
slewing: 32
vscale: 4
stroke: "#0000FFAA"
stroke-dasharray: [1, 3]
fill: "#0000FF"
order: 2
analogue:
- "VDDA*512/1024"
- "VDDA*256/1024"
- "VDDA*384/1024"
- "VDDA*320/1024"
- "VDDA*352/1024"
- "VDDA*336/1024"
- "VDDA*344/1024"
- "VDDA*340/1024"
- "VDDA*342/1024"
- "VDDA*341/1024"
then generate an image with undulate
undulate -f svg -i step_2_ana.yaml -o step_2_ana.svg
set the content of the file to
# testcase to demonstrate the possibility
# of overlaying several curves
mcu_clk.wave = "P"
mcu_clk.repeat = 10
# value of the 10-bits DAC of a SAR
dac.wave = "c"
dac.repeat = 10
dac.slewing = 32
dac.vscale = 4
dac.overlay = true
dac.stroke = [0, 0, 255, 255]
dac.stroke-dasharray = [1, 3]
dac.fill = [0, 0, 255, 255]
dac.font-size = '9pt'
dac.order = 2
dac.analogue = [
"VDDA*512/1024",
"VDDA*256/1024",
"VDDA*384/1024",
"VDDA*320/1024",
"VDDA*352/1024",
"VDDA*336/1024",
"VDDA*344/1024",
"VDDA*340/1024",
"VDDA*342/1024",
"VDDA*341/1024"
]
# input voltage to which compare
vin.wave = "0a........"
vin.vscale = 4
vin.overlay = true
vin.stroke = '#F00'
vin.stroke-dasharray = [5, 3, 1, 5]
vin.stroke-width = 1.5
vin.fill = 'rgb(255, 0, 0)'
vin.font-size = '0.4em'
vin.order = 3
vin.analogue = [
"[(t, (VDDA/3)*(1-exp(-t/3))) for t in time]"
]
# vmax
vmax.wave = "1........."
vmax.vscale = 4
vmax.order = 1
vmax.overlay = true
# vmin
vmin.wave = "l........."
vmin.vscale = 4
vmin.order = 4
dac_ref.wave = "s"
dac_ref.repeat = 10
dac_ref.slewing = 32
dac_ref.vscale = 4
dac_ref.stroke = '#0000FFAA'
dac_ref.stroke-dasharray = [1, 3]
dac_ref.fill = '#0000FF'
dac_ref.order = 2
dac_ref.analogue = [
"VDDA*512/1024",
"VDDA*256/1024",
"VDDA*384/1024",
"VDDA*320/1024",
"VDDA*352/1024",
"VDDA*336/1024",
"VDDA*344/1024",
"VDDA*340/1024",
"VDDA*342/1024",
"VDDA*341/1024"
]
then generate an image with undulate
undulate -f svg -i step_2_ana.toml -o step_2_ana.svg
Note
To enhance the clarity, the following property can be overloaded as in the example:
font-size:
size of the text (valid css units in em, px, pt)fill:
color of area and text (valid css color in hex, rgb, rgba)stroke:
color of lines (valid css color in hex, rgb, rgba)stroke-width:
thickness of linesstroke-dasharray:
pattern of dash to apply described as an array of number representingalternatively line segment length, spacing length
Tip
To enhance lisibility, the line have been made bigger by using vscale. It accepts
a scaling factor as done in the example.
It also exists hscale scaling the x-axis instead of the y-axis as vscale does.