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Jun 20, 2007, 01:04 PM
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Massive software overflow


So with Vicacopter, we have a huge amount of software to write for the next test flight. The problem is telemetry. The need for intense PID loop calibration made us move the 2 way communication phase forward. Originally 2 way communication was optional.

The real problem was getting a portable ground interface. Laptop batteries don't last long enough. PDA's are unaffordable. Then, remembered we had a graphic calculator with RS232 support and a terminal emulator. It lasts many hours on batteries. So the ground interface is a text console with all the computation done on the airframe and the calculator as a dumb terminal.

You can buy a wireless modem suitable for Vicacopter for $300, but we need $300 for batteries. Instead, this is a matter of stacking the telemetry packets on the existing carriers and implementing wireless flow control.

With the unreliable wireless communication, we need 4 bit flow control. The data buffer and flow control bits are repeated over and over on each wireless channel. It's super slow but good enough for PID calibration. The problem with this is each packet is going to be repeated twice while it waits for the ACK packet. We're not going to try to optimize it with delays.

Data ready - toggles when we have new data in the outgoing buffer
Data ready ACK - toggles when we have receieved new data in the incoming buffer
Reset - set to 1 when outgoing data ready is reset to 0
Reset ACK - set to 1 when the incoming reset is receieved
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