Version Details
v1 Original 2010-2011 Orbcomm CommController
v2 2011-2012 Iridium Comm Controller

Communications Controller Module v1

This module will communicate with other modules, including the flight computer through the main I2C bus. The purpose of this module is to interface with the Iridium 9602 Satellite Data Modem, and optionally two external serially .

Overview of comm Ctrlr activities

  • Sending telemetry Messages to Sat Modem
  • Receiving Uplink messages from Sat modem
    • Pass Uplink Messages on to I2C bus addressed to other modules
  • Sending telemetry Messages to HF Radio
  • Send commands to cutdown


Google Spreadsheet Comm Ctrlr BOM

Main Onboard Devices:

  • Arduino FIO
    • XBee for sensor comms
  • Sat modem connector
  • I2C storage EEPROM(s)
  • Connector for VHF APRS ASCII Serial output
    • PWR5, PWR3.3, PWR12, TX, RX, GND
  • Connector for HF ASCII Serial output
    • PWR5, PWR3.3, PWR12, TX, RX, GND
  • Main Bus connector
  • Power Decoupling
    • One 1000uf Electrolytic 25v Cap, 5 0.1uf 0804 surface mount caps stacked in paralle.

Connector Interfaces

White Star Bus
Arduino FIO

See Arduino FIO documentation

Digi m10
Pin Function
1 PWR12
3 PWR12
5 Power Enable
7 SAT Host Serial Port RX
9 SA Satellite Available
10 DA Data Available
11 Debug Serial Port TX
12 Debug Serial Port RX
13 SAT Host Serial Port RTS
14 SAT Host Serial Port CTS
External Transmitter 1
Pin Function
1 PWR12
2 PWR3.3
3 PWR5
5 Serial data from ExtTX
6 Serial data to ExtTX
External Transmitter 2
Pin Function
1 PWR12
2 PWR3.3
3 PWR5
5 Serial data from ExtTX
6 Serial data to ExtTX
Strobe/External IO
Pin Function
1 PWR12
3 External I/O 1

Software v1

Inbound I2C Commands

Command Action Data Required Format Sat Uplink ok
0x00 Transmit ATC Short Report 12 bytes See Note below
0x01 Transmit Data from I2C EEPROM 4 bytes 2B Start Addr, 2B End Addr
0x02 Update HF Telemetry values 3 byte Val0, Val1, Val2
0x03 Transmit HF short position report 0 byte
0x04 Set HF transmit rate 1 byte ASCII 'H', 'M' or 'L'
0x05 Mute HF for 2 minutes 0 byte
0x06 Reset cutdown heartbeat timer 0 byte Y
0x07 Set cutdown timer to X minutes, and reset 1 byte 0-255 Y
0x99 CUTDOWN NOW 0 bytes Y
0xBB Power up sat modem 0 bytes
0xAA Power down sat modem 0 bytes

Satellite Module Interfacing: Digi m10

For radio interfacing details see also:

General scheme

The The m10 will toggle a logic line high when it has received a message. This signal should interrupt wake up the communications module MCU if it is in sleep mode. The MCU should then read in the message from the m10 module, and pass it on to the appropriate destination. The address of the destination module will be part of the 5-byte command.


The balloon cutdown module will have a short cutdown timer. This timer will be on the order of 30 minutes or so. The timer will be reset by an I2C message from the comms module every time the comms module receives any message from the satellite modem. That means, in addition to forwarding the uplinked message over the I2C bus, you will need to immediately send a direct “reset the counter” heartbeat I2C message over the bus to the cutdown module.

Message content

Message content destined for the sat modem or HF modem will be passed raw from module to module if possible, this will reduce the need to change firmware on the comms module.

Message timing

Messages to be transmitted are to be transmitted immediately upon receipt by the comms module.

Status requests

Comms module should be able to respond with a configuration request listing which radios are connected (Sat, HF, VHF). Also should have a status available of all radios, with information such as:

  • TX Status (is it transmitting right now)
  • How many messages are waiting to be transmitted

PCB Jumper Settings

Bold indicates REQUIRED connections for flight.

  1. IORST
    1. This chooses where to connect the WS GPIO pin from the Flight computer
    2. Options
      1. FIO I/O Pin A7
      2. FIO DTR/Reset pin
  2. DTX
    1. SAT Debug Serial Port TX line
    2. Options
      1. DBG
      2. MCU
  3. DRX
    1. SAT Debug Serial Port RX line
    2. Options
      1. DBG
      2. MCU
  4. TX
    1. SAT HOST Serial Port TX line
    2. Options
      1. HOST
      2. MCU
  5. RX
    1. SAT HOST Serial Port RX line
    2. Options
      1. HOST
      2. MCU

hardware/comms/v2.txt · Last modified: 2018/07/29 17:58 (external edit)
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