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This repository contains hardware designs and software for the liteRF project, a low cost, open source Software Defined Radio platform based on the popular HackRF design by Great Scott Gadgets.

This is a living project and thus not suitable for manufacturing or any use. You have been warned.

We want to reduce the cost and availability problems with the parts chosen for the original HackRF.
Our target is to at least halve the BOM cost and avoid as many of the unobtainium and obsolete parts.
Especially those by Maxim.

This whole project started with me finding AT86RF215's on Digikey one night and discovering their IQ interface.
It was re-invigorated by the CaribouLite project also named Lite and using the AT86RF215.

(photo by fd0 from https://github.com/fd0/hackrf-one-pictures)

This is the original hackRF, want to make it cheaper and to avoid problems with unobtainium parts.

Because all great artists steal, we will consider existing related projects when choosing parts.
As that gives us access to existing, proven designs with support from the community.

1. Maxim MAX2837+MAX5864 replaced by Microchip AT86RF215. Cheaper, more available.
2. Xilinx XC2C64A-7VQG100C CPLD replaced with Lattice ICE40LP1k-QN84
3. SiLabs/Skyworks Si5351C replaced by Hangzhou Ruimeng Tech MS5351M. Cheaper, AVAILABLE. Might require two or rethinking clocks.

Some links to candidate parts and information on them below.

Both of these are expensive and hard to find. It might change now that Analog Devices owns Maxim, or get worse.
Replacing these is the origin of this project. I had a terrible time sourcing them for my hackRF build.

MAX2837 info:
https://www.maximintegrated.com/en/products/comms/wireless-rf/MAX2837.html
Datasheet: https://datasheets.maximintegrated.com/en/ds/MAX2837.pdf

MAX5864 info:
https://www.maximintegrated.com/en/products/analog/data-converters/analog-front-end-ics/MAX5864.html

MAX2837 covers 2300-2700MHz in turn AT86RF215 covers only a part of the same spectrum. The 2400-2400-2483.5MHz ISM band. This is not a major problem as hacKRF uses a 2.4GHz IF with a SAW filter.
This is compatible with using AT86RF215.

AT86RF215 info: https://www.microchip.com/en-us/product/AT86RF215 Datasheet: https://ww1.microchip.com/downloads/en/DeviceDoc/45099A-AT86RF215_E_US_102714_Web.pdf

0 stock and 52 week lead time on Digikey, nuff said:
https://www.digikey.fi/en/products/detail/xilinx-inc/XC2C64A-7VQG100C/949460 Datasheet: https://docs.xilinx.com/v/u/en-US/ds311

In addition to sourcing problems, a 64 macrocell CPLD can't do what we want to the 128Mbit/second 64MHz DDR clocked LVDS interface AT86RF215 has.
Thus we replace it with Lattice ICE40LP1k-QN84. This has a FOSS toolchain and a free tool chain from the manufacturer.
It is used in the CaribouLite, so it works with AT86RF215 amd the gateware is under a permissive license. So we are not starting from 100% scratch.
We need some fast programmable gluelogic here and Lattice iCE40 is a good choise due to low cost, good FOSS community and okay-ish availability.
I might have to reconsider this if I cannot source it or any iCE40 device with the same or larger amount of LUT's. I'm open to suggestions.
iCE40LP family datasheet: https://www.latticesemi.com/~/media/LatticeSemi/Documents/DataSheets/iCE/iCE40LPHXFamilyDataSheet.pdf

Skyworks Si5351C is in QFN case and has 8 outputs, compared to MS5351M's 3, so some work is likely needed. But they are register compatible and MS5351M 1:1 replaces Si5351B in almost all applications.
This requires further thought in the clock tree side of things.

Source and datasheet.
https://lcsc.com/product-detail/Clock-Generators-Frequency-Synthesizers-PLL_Hangzhou-Ruimeng-Tech-MS5351M_C1509083.html

QRP-Labs investigation that finds MS5351 meeting or exeeding Si5351.
http://www.qrp-labs.com/synth/ms5351m.html

Si5351C stock situation:
https://octopart.com/si5351c-b-gm-silicon+labs-24879781

1. NXP LPC4320FBD144 MCU substitution with something cheaper and more available.
2. TI TPS62410 dual VREG with two Microchip switchers and point of load low noise LDO's for RF. Due to availability and noise.
3. Skyworks SKY13317 RF switch with Maxcend MXD8641. Due to price and availability. Also for better frontend.

Some links to candidate parts and information on them.

NXP LPC4320FBD144 has:
ARM Cortex-M4F core capable of 204MHz and a Arm Cortex-M0 co-processor running at frequencies up to 204MHz.
200kB SRAM High-speed USB 2.0 Host/Device interface.

I'm unsure if this is fast enough. It's RISC-V! Datasheet+SDK https://github.com/openwch/ch32v307

LQFP100 case https://lcsc.com/product-detail/Microcontroller-Units-MCUs-MPUs-SOCs_WCH-Jiangsu-Qin-Heng-CH32V307VCT6_C2943979.html

Used in iCEBreaker 1.99 hardware with Lattice iCE40UP5K.

i.MX RT1024 Cortex-M7 @500 MHz 256 kB SRAM 144 LQFP i.MX RT1020 Cortex-M7 @500 MHz 256 kB SRAM 100 LQFP & 144 LQFP

Octopart shows some stock, but only direct from TI or from Farnell, which is stingy about selling to individuals
This is annoying and thus needs a good replacement.

TPS62410 product page with info and datasheet:
https://www.ti.com/product/TPS62410

Source and data. https://lcsc.com/product-detail/RF-Switches_Maxscend-MXD8641_C285559.html

NanoVNA v2, they use Maxcend switches and later also MS5351M.
https://github.com/nanovna-v2/NanoVNA2

Other Maxcend RF swithces are also available on LCSC.net (https://lcsc.com/products/RF-Switches_980.html?brand=11684)

Needs to be cheaper than what it's replacing.
If not cheaper, then more available.
If possible, already used and thus qualified by somebody else. Possibly lower risk of surprises that way.
Higher performance than what it is replacing.
Easier to use use than what it is replacing.
If possible, the case should be easily soldered and inspected. So more QFN and TQFP, less BGA and LGA.
Available from JLCPCB SMT assembly, LCSC.com , TME.eu, Mouser or Digikey.

PROPER REF DES on PCB.

One of these days I'll clean this up and use the wiki for all the component talk.

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