We are having trouble with our cut down system. We are trying to determine if it is the XBee connection or some issue with the Iridium modem. Does anyone know if the Xbees are talking to each other can you run the motor manually from the OCCAMS board? If this can't be done can you connect a serial port to the Iridium input on the OCCAMS side and using a terminal program send the cut command? If so what does the cut command look like?
There are three different systems that could be the problem.
Iridium – The first thing to check is that the Iridium modem is setting the correct output pins as high or low. Simply use a thin wire and a multimeter (I find that paperclips are the perfect gauge) on the female db connector on the Iridium modem to see which pins are 5 and 0 volts. Page 8 of the OCCAMS documentation (https://docs.google.com/document/d/1cIViwz_OIWYr0xSAEMsAJhY3k9FNei9cega3LxPirQQ/edit) lists what each of the Iridium pins are being used for. If it appears that your modem is outputting the correct bits (the default cut down command is 001) then try sending the idle command (000) verify that all output pins are low and then resend the cut down command. If the correct pin states are set then congratulations, your expensive modem is not broken!
OCCAMS – For each OCCAMS board make sure that the timer has been properly reset (both the OCCAMS documentation and the launch checklist cover how to do this) and then press the manual termination button (labeled MOTOR on the board) and verify that the motor (preferably without the blade attached) starts spinning (or use a multimeter on the JP3 pins). If this works and the boards are beeping at 1 second intervals, then most of the OCCAMS board works. The best way to verify that both OCCAMS boards work without relying on the XBees is to simply wait 4-5 hours for the onboard timer to runout and activate the cut down motor. If both boards activate the motor after the timer runs out then congratulations, your OCCAMS boards are (most likely) not broken!
XBee – Now for the fun one. If you have verified that both the Iridium modem and the OCCAMS boards are working as they should, then the problem is most likely with the XBee’s (some unlikely but still possible choices are listed below). To troubleshoot the XBee’s you will need two XBee Explorers (https://www.sparkfun.com/products/11812) and a computer with the X-CTU (http://www.digi.com/products/wireless-wired-embedded-solutions/zigbee-rf-modules/xctu) program installed. Sparkfun has a wondrously detailed XBee and X-CTU guide (https://learn.sparkfun.com/tutorials/exploring-xbees-and-xctu) that should help you verify that both XBee’s are working and talking to each other.
Other – If you have tried all three previous steps and still can’t get the cut down system to work then there are a few other things that could be happening. The cut down motor could be bad, this can be verified with a multimeter hiked us to the jp3 header that the motor is plugged into. XBee signal could be being blocked, reflected or they are too far away. Some buildings/rooms do weird things to the wireless signal. The surefire way to eliminate this is to take the system outside and keep the XBee’s in line of sight.
To answer your other questions: The motor button on each OCCAMS board will manually start the motor. Or, if you were wondering if you can use the system with only one OCCAMS and no XBee’s; that is possible but your cut down payload and Iridium payload will have to be the same payload. The cut down command isn’t even serial, it’s simply a three bit value. The default cut down command is 001 which on a db15 connector is pins 7 and 8 at 0V and pin 15 at 5V.
Hope this helped, Gabriel Walker Colorado Space Grant