sigrok - User contributions [en]

BG7TBL

2018-05-21T12:13:35Z

Xof: /* Spectrum analyzer */ + code sample & ref.

{{Infobox signal generator
| image = [[File:BG7TBL_case.jpg|180px]]
| name = BG7TBL
| status = planned
| source_code_dir =
| frequser = 138MHz-4.4GHz
| waveforms = sine (fixed)
| amplitude = ? V
| connectivity = USB
}}
The BG7TBL USB RF Signal Generator is a PC-based function generator. It has no external controls, requiring a USB connection to a computer.

Software to run this hardware can be found here http://www.dl4jal.eu/.

This device can be bought on ebay for ca $65. Search for "138MHz-4.4GHz". There is a version with the ADF4351 instead that will give you more range (35MHz-4.4GHz).

== Hardware ==
* Microcontroller: [http://www.atmel.com/Images/Atmel-2486-8-bit-AVR-microcontroller-ATmega8_L_datasheet.pdf Atmel Atmega 8L]
* Wideband Synthesizer: [http://www.analog.com/media/en/technical-documentation/data-sheets/ADF4350.pdf ADF4350]
* USB to Serial: [http://www.ftdichip.com/Support/Documents/DataSheets/ICs/DS_FT232R.pdf FTDI FT232RL]
* Logarithmic Amplifier [http://www.analog.com/media/en/technical-documentation/data-sheets/AD8307.pdf AD8307]
* Mixer: [http://www.qsl.net/n9zia/omnitracs/IAM81008.pdf IAM 81008]
* LDO: [http://www.advanced-monolithic.com/pdf/ds1117.pdf AMS1117]

== Photos ==

<gallery>
BG7TBL pcb top.jpg
BG7TBL pcb bot.jpg
</gallery>

== Protocol ==
Baud 57600, 8n1

The protocol is binary serial based.

=== Query firmware ===

* Send 0x8f+"v"

The answer should be in hex:

* 77

Where the returned byte is the firmware version, 0x77 = 119 = 'w'.
<pre>
#!/usr/bin/python

import serial

ser = serial.Serial('/dev/ttyUSB0', 57600, timeout=1) # Linux first FTDI
ser.write("\x8f" + "v")
print("version is " + ser.read())
</pre>

=== Signal generator ===
==== Setting frequency ====
To set a frequency send:

* 0x8f

Then f and then the frequency divided by 10 with leading zeroes. For example this is the payload for 400MHz.

* 400 000 000 / 10
* f040000000
<pre>
#!/usr/bin/python
import sys, serial

ser = serial.Serial('/dev/ttyUSB0', 57600, timeout=1) # Linux first FTDI
# sys.argv[1] is frequency in Herz
cmd = "\x8f" + "f" + '{:09d}'.format(int(sys.argv[1])/10)
ser.write(cmd)
</pre>

=== Spectrum analyzer ===

The protocol is briefly described in the source code here:

https://github.com/DoYouKnow/BG7TBL_Reader

Here is a minimal code for an 'x' sweep <small>(the protocol is described in chapter 6 of http://www.dl4jal.eu/LinNWT_doc_en.pdf )</small>. The device sends back the expected number of bytes but it seems I have to divide the frequency by 10... (?).
<pre>
#!/usr/bin/python
import sys, serial, struct

start_frequency = 100000000 # FM band
increment = 20000
steps = 2000
#
# 'x' sweep (writing the command returns (4 * steps) bytes (what is it, I don't know)
#
cmd = "\x8f" + "x" + '{:09d}{:08d}{:04d}'.format(start_frequency/10, increment, steps)
ser = serial.Serial('/dev/ttyUSB0', 57600, timeout=100) # Linux first FTDI
ser.write(cmd)
rsp = ser.read(4 * steps)
if len(rsp) < (4 * steps):
sys.stderr.write("Warning : Did not read enough measures! Try increasing the timeout\n")
steps = len(rsp)/4 # adapt to the number of measures read
val_tab = struct.unpack_from("<" + "h"*2*steps, rsp) # 2 * steps 'little endian shorts'
for i in range(0, steps):
print(val_tab[2*i]) # channel A (A and B are interleaved)
</pre>

BG7TBL

2018-05-20T08:41:15Z

Xof: /* Setting frequency */ + prog. example in Python

BG7TBL

2018-05-19T07:00:26Z

Xof: /* Protocol */ + sample code to check the firmware (4 Python lines)

BG7TBL

2018-05-19T06:51:05Z

Xof: /* Query firmware */ firmware version is also 'w'