Sweep and Measurement Commands

Commands for controlling frequency sweep and measurement parameters.

scan

Perform a frequency sweep and output measured data.

Syntax

scan <start> <stop> [points] [outmask]

Parameters

Parameter	Description	Default
`start`	Start frequency in Hz	Required
`stop`	Stop frequency in Hz	Required
`points`	Number of sweep points (1–401)	Current setting
`outmask`	Output control bitmask (see below)	0 (no per-point output)

Outmask Bits

The outmask parameter is a bitmask controlling both what data is output and how it is processed:

Bit	Value	Name	Description
0	`1`	`OUT_FREQ`	Include frequency (Hz) for each point
1	`2`	`OUT_DATA0`	Include S11 real/imaginary pair
2	`4`	`OUT_DATA1`	Include S21 real/imaginary pair
3	`8`	`NO_CALIBRATION`	Skip calibration correction
4	`16`	`NO_EDELAY`	Skip electrical delay compensation
5	`32`	`NO_S21OFFS`	Skip S21 offset correction

Common mask values:

7 = frequencies + S11 + S21 (calibrated)
6 = S11 + S21 data only (no frequencies)
15 = frequencies + S11 + S21, uncalibrated raw data

Output Format

For each point, outputs selected fields separated by spaces:

[frequency] [S11_re S11_im] [S21_re S21_im]

Examples

ch> scan 1000000 100000000 101 7
1000000 0.998234 -0.023456 0.012345 0.001234
1990099 0.997234 -0.024567 0.012456 0.001345
...

ch> scan 1M 100M 101 6
0.998234 -0.023456 0.012345 0.001234
...

ch> scan 1M 100M 101 14
0.998234 -0.023456 0.012345 0.001234
...

Notes

Interrupts any ongoing sweep
Applies current calibration (unless bit 3 is set)
Data is in linear format (not dB)
With outmask 14 (OUT_DATA0 | OUT_DATA1 | NO_CALIBRATION), you get raw uncalibrated S-parameters

scan_bin

Binary output variant of scan for faster data transfer. Accepts the same arguments as scan but forces binary output mode regardless of the outmask BINARY bit.

Syntax

scan_bin <start> <stop> [points] [outmask]

Binary Output Format

The output begins with a 4-byte header, followed by per-point data:

Header (4 bytes):

Field	Type	Size	Description
`mask`	`uint16_t`	2 bytes	Outmask with `BINARY` bit (0x80) set
`points`	`uint16_t`	2 bytes	Number of sweep points

Per-point data (variable size):

Field	Type	Size	Condition
`frequency`	`uint32_t`	4 bytes	If mask bit 0 (`OUT_FREQ`) set
`S11_re, S11_im`	`float[2]`	8 bytes	If mask bit 1 (`OUT_DATA0`) set
`S21_re, S21_im`	`float[2]`	8 bytes	If mask bit 2 (`OUT_DATA1`) set

All values are little-endian. Floats are IEEE 754 single precision.

Example Usage

import struct
import serial

ser = serial.Serial('/dev/ttyACM0', 115200, timeout=5)
ser.write(b'scan_bin 1000000 100000000 101 7\r')

# Read 4-byte header
header = ser.read(4)
mask, points = struct.unpack('<HH', header)

# Calculate bytes per point based on mask bits
bytes_per_point = 0
if mask & 0x01: bytes_per_point += 4   # frequency (uint32)
if mask & 0x02: bytes_per_point += 8   # S11 (2 floats)
if mask & 0x04: bytes_per_point += 8   # S21 (2 floats)

data = ser.read(points * bytes_per_point)

# Parse each point
offset = 0
for i in range(points):
    if mask & 0x01:
        freq = struct.unpack_from('<I', data, offset)[0]
        offset += 4
    if mask & 0x02:
        s11_re, s11_im = struct.unpack_from('<ff', data, offset)
        offset += 8
    if mask & 0x04:
        s21_re, s21_im = struct.unpack_from('<ff', data, offset)
        offset += 8

sweep

Get or set sweep frequency range and points. Supports both positional arguments and named subcommands for individual parameter control.

Syntax

sweep                                  # query current settings
sweep <start> [stop] [points]          # set range (positional)
sweep {start|stop|center|span|cw|step|var} <value>  # set individual parameter

Positional Parameters

Parameter	Description	Range
`start`	Start frequency in Hz	600 Hz – 2 GHz
`stop`	Stop frequency in Hz	600 Hz – 2 GHz
`points`	Number of sweep points	1–401 (F072) or 1–101 (F303)

Named Subcommands

Subcommand	Description
`start`	Set start frequency only
`stop`	Set stop frequency only
`center`	Set center frequency (adjusts start/stop symmetrically)
`span`	Set frequency span (adjusts start/stop around center)
`cw`	Set CW frequency (single-point sweep)
`step`	Set frequency step size between points
`var`	Set variable parameter (for parameter sweep modes)

Examples

ch> sweep
1000000 100000000 101

ch> sweep 50k 300M
ch> sweep 1M 100M 201

ch> sweep center 145M
ch> sweep span 10M
ch> sweep cw 432.1M
ch> sweep step 100k

Notes

With no arguments, returns current settings: start stop points
Named subcommands accept exactly 2 arguments: the keyword and a frequency value
Setting sweep parameters triggers recalculation of frequency points and may require calibration interpolation

freq

Set or get CW (single frequency) mode.

Syntax

freq [frequency]

Parameters

Parameter	Description
`frequency`	CW frequency in Hz

Examples

ch> freq
145000000

ch> freq 145M
ch> freq 432.100M

Notes

Sets sweep to single point at specified frequency
Useful for continuous monitoring at one frequency
Equivalent to sweep <freq> <freq> 1

power

Set or get output power level.

Syntax

power [level|auto]

Parameters

Value	Description
`auto` or `255`	Automatic power selection
`0`	2 mA drive
`1`	4 mA drive
`2`	6 mA drive
`3`	8 mA drive

Examples

ch> power
auto

ch> power 2
ch> power auto

Notes

Higher power improves dynamic range but may cause compression on some DUTs
Auto mode selects power based on frequency band

bandwidth

Set or get IF (intermediate frequency) bandwidth.

Syntax

bandwidth [bw]

Parameters

Value	Bandwidth	Sweep Speed
`4000`	4000 Hz	Fastest
`2000`	2000 Hz	Fast
`1000`	1000 Hz	Medium
`333`	333 Hz	Slow
`100`	100 Hz	Slower
`30`	30 Hz	Slowest

Examples

ch> bandwidth
1000

ch> bandwidth 100

Notes

Lower bandwidth = more averaging = less noise but slower
For accurate measurements of narrow filters, use lower bandwidth
Default is 1000 Hz

pause

Pause continuous sweep.

Syntax

pause

Example

ch> pause

Notes

Sweep stops at current position
Data remains valid
Use resume to continue

resume

Resume paused sweep.

Syntax

resume

Example

ch> resume

Notes

Continues sweep from where it was paused
If sweep was not paused, has no effect

offset

Set frequency offset (if USE_VARIABLE_OFFSET enabled).

Syntax

offset [value]

Parameters

Parameter	Description
`value`	Frequency offset in Hz

Notes

Used for external mixers or frequency converters
Adds offset to displayed frequencies

Sweep Mode Flags

The firmware maintains sweep mode flags:

Flag	Value	Description
`SWEEP_ENABLE`	0x01	Continuous sweep enabled
`SWEEP_ONCE`	0x02	Single sweep requested
`SWEEP_UI_MODE`	0x04	Processing UI (not sweeping)

Timing Considerations

Sweep timing depends on:

Number of points: More points = longer sweep
IF bandwidth: Lower bandwidth = longer per point
Frequency range: Band changes add settling time

Approximate times for 101 points:

Bandwidth	Time
4000 Hz	0.7 s
1000 Hz	1.2 s
333 Hz	3.6 s
100 Hz	10 s
30 Hz	33 s

Source Code Reference

Command implementations in main.c:

cmd_scan: line 1379 — scan mask definitions at line 1371
cmd_scan_bin: line 1454
cmd_sweep: line 1606 — subcommand parsing with get_str_index
cmd_freq: line 621
cmd_power: line 642
cmd_bandwidth: line 1294
cmd_pause: line 500
cmd_resume: line 507
cmd_offset: line 610 (conditional: USE_VARIABLE_OFFSET)