[Ground-station] 31 May 2018 IHU Meeting Minutes

Jonathan Brandenburg jonathan at jonathanbrandenburg.com
Wed Jun 6 11:40:34 EDT 2018

Yes, the HDLC encoding of the AX5043 appears to be the framing and
modulation required by AX.25. My next task is to create a sample
application for the Digital Transceiver for the Raspberry Pi (that's
what I call the Raspberry Pi dev board with the AX5043) that transmits
APRS. It will be based on work done by Libre Space Foundation that has
reportedly developed APRS for AX5043 using a STM32 processor (see

The reference code for the sample software developed for the Digital
Transceiver for the Raspberry Pi is located at
https://github.com/BrandenburgTech/DigitalTxRxRPi. I'll be publishing
the hardware files as soon as that task hits the top of my task list (so
many fun and necessary tasks but so little time in a day). In the
meantime, I can provide assembled boards as I get parts and assemble them.

Of course, when I get the hardware files published, you can build your
own (and improve the board).


On 6/5/2018 11:48 AM, Zach Leffke via Ground-Station wrote:
> This is awesome!  to fixate on one detail, that is not related to the
> IHU..........I'm very interested in the AX5043 (particularly the
> native HDLC features, which sound suspiciously close to AX.25 with a
> little help from the Pi/MCU).  Will the Raspberry Pi dev board /
> reference code also be on github at the link provided?  any ETA for
> that? Does that already exist somewhere on github?
> Thanks!
> -Zach, KJ4QLP
> Research Associate
> Aerospace Systems Lab
> Ted & Karyn Hume Center for National Security & Technology
> Virginia Polytechnic Institute & State University
> Work Phone: 540-231-4174
> Cell Phone: 540-808-6305
> On 6/5/2018 11:54 AM, Michelle Thompson via Ground-Station wrote:
>> A conference call was held on 31 May 2018. Presenting was Jonathan
>> Brandenburg, concerning his IHU project that he wishes to publish. 
>> Open Research Institute will support publishing this open source
>> Integrated Housekeeping Unit (IHU) design intended for amateur radio
>> satellite service payloads. An IHU is a flight computer, controlling
>> all the elements of the payload.
>> The call was held courtesy of National Instruments conference bridge.
>> Thank you to Neel Pandeya for making it possible and for supporting
>> open source hardware and software designs. 
>> The design team for this IHU consists of Zach Metzinger, Jordan
>> Trewitt, Bill Reed, and Jonathan Brandenburg. This started in earnest
>> about a year ago. It it not radiation hardened by design, but is
>> entirely appropriate for low earth orbit (LEO) use. 
>> Initial design work was presented at the 2017 AMSAT Symposium. 
>> This is a failover IHU design. It was two fault-tolerant processors.
>> The processor is TI Hercules and the part number is TMS570LS0914PGE.
>> Each processor has two cores, and each core operates in lock-step.
>> There is some flight heritage with this part from the ICI Radar
>> Satellite and a NASA Robotic ARM. 
>> Included in the design are twin transceivers. The transceiver
>> selected is the AX5043.
>> A power amplifier design is in progress. 
>> There is error correction on the memories. 
>> This IHU has two “sides”, with one Hercules and one transceiver on
>> each side. There is diversity in the voltage regulators, with the
>> primary side powered by a MAX1556A regulators and a secondary side
>> powered with LTI963As. The diversity in voltage regulators is
>> intended to provide additional resilience. For each side, there is a
>> 3.3volt rail and a 1.2volt rail.
>> Software development has only just begun. Layout is approximately 80%
>> complete. 
>> The board has 4 layers and relatively good power consumption based on
>> prototype measurement. 
>> UPSat from Libre Space was also introduced and referenced.
>> OreSat is interested in collaborating and learning more about this
>> design.
>> Our consensus is CANbus or Ethernet for flight hardware.
>> Jonathan has also made a Raspberry Pi daughterboard for the AX5043.
>> This allows development with the transceiver independent of the
>> Hercules or IHU. 
>> The drawbacks to the Hercules include terrible documentation and a
>> cumbersome parameterized code generation process for development.
>> Jonathan believes he is getting a handle on this and there is the
>> possibility of him producing improved documentation for this design. 
>> We also discussed the VA10820 - Radiation Hardened ARM® Cortex®-M0
>> MCU https://www.voragotech.com/products/va10820. This is
>> approximately $700, but has good stats and a well-documented
>> toolchain. There is at least one design that is open source that
>> could be used as a basis for an IHU. 
>> Jonathan to publish the IHU at https://github.com/phase4space/payload-IHU
>> Jonathan and Michelle to press for review of the design.
>> Michelle to publish minutes.
>> Michelle to arrange for additional IHU conference calls. 
>> Microsemi’s SmartFusion2 and PolarFire devices were brought up
>> outside of the meeting.  They are actively advertising radiation
>> hardening for these parts and they may be available now and should be
>> discussed. 
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Jonathan Brandenburg
jonathan at jonathanbrandenburg.com
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