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osmo-fl2k

Osmo-fl2k is a project that uses Fresco Logic FL2000 based USB3.0 Dongles as SDR transmitters.
The linked project pages [0], [1] have more details. 

This page documents my experiments with FL2000 based dongles and osmo-fl2k. 

Unfortunately no public datasheet for this chip exists and the manufacturers page for it [2] is sparse with details. 
So I did some reversing and currently have come up with these details:
The supply voltage is 3.3V and 1.2V, of which the analog core seems to be fed with 1.2V. 
In the ICZI branded dongle with "MINE UV110" silkscreened on the pcb, these are done with two switch mode regulators. 

 Pin Definition Pin Definition Pin Definition
 1 Decoupled by C1 20 FT 39 FT Pin36
 21.2V VCC 21 FT 40 FT
 3 ? 22 USB GND via C12 41 1.2V VCC
 4 ? 23 USB GND via C13 42 GND
 5 Decoupled by C26 24 USB TXN 43 FT + Decoupled by C20
 6 SPI FLASH as USB Storage enable. Ground to disable. 25 USB TXP 44 1.2V VCC
 7 ? 26 FT 45 1.2V VCC
 8 Decoupled by C22 27 USB RXM 46 FT + Connected to Pin43
 9 EEPROM PIN6 SPI CLK 28 USB RXP 47 FT and decoupled by C29+C30
 10 EEPROM PIN1 SPI /CS 29 FT 48 1.2V VCC, FT
 11 EEPROM PIN3 SPI /WP 30 FT 49 FT
 12 EEPROM PIN7 SPI /HOLD
 31 FT 50 FT
 13 EEPROM PIN5 SPI DI 32 NC? 51 VGA RED
 14 NC? 33 NC? 52 FT
 15 1.2V VCC 34 FT 53 VGA GREEN
 16 XTAL1 35 NC 54 VGA BLUE
 17 XTAL2, connected to 22R 36 FT & Pin39 55 GND
 18 USB DP 37 FT & Pin38 56 1.2V VCC Analog?
 19 USB DM 38 FT & Pin37 57 Thermal pad
*FT = Connected to something on the other side of the board.

Both 1.2V and 3.3V voltages are made from USB 5V with SOT23-5 cased regulators marked "A17E".
These might to be Texas Instruments TLV6256x series step-down regulators.
The spurs observed by others do seem to be at around 1.5MHz intervals, which corresponds to the typical 1.5MHz switching frequency used by these. Not that MHz switching speeds are anything special these days, so it might be a compatible clone.
Datasheet: http://www.ti.com/lit/ds/symlink/tlv62565.pdf


The other side of the board has 4pcs SOT-23 transistors marked "702", these seem to be 2N7002 N-channel MOSFETs.
Winbond W25Q64FV EEPROM datasheet [3]

[0] https://osmocom.org/projects/osmo-fl2k/wiki/Osmo-fl2k
[1] https://github.com/steve-m/fl2k-examples
[2] http://www.frescologic.com/product/single/fl2000
[3] https://www.pjrc.com/store/w25q64fv.pdf

Stuff to do with it and clickbait:
http://laforge.gnumonks.org/blog/20180423-osmo-fl2k/
https://www.rtl-sdr.com/setting-up-and-testing-osmo-fl2k/
https://hackaday.io/project/21145-am-band-voice-frequency-marker
http://tinyhack.com/2018/05/05/fixing-osmo-fl2k-dongle-that-only-works-in-usb-2-0/
https://hackernoon.com/osmo-fl2k-a-15-dtv-transmitter-fm-radio-hijack-and-gps-spoofing-device-68ac08ba7d76 (clickbait but has good info)
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