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Question about Ultimate GPS library
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Question about Ultimate GPS library

by mmessiter on Fri Jan 14, 2022 1:33 pm


This week I'm adding GPS support to my LockDownRadioControl project (all my code is on Github if you're interested).

The Adafruit Ultimate GPS device works really well and since it can use i2c, I connected it quickly and easily to existing receivers
and just added code!

All works very well indeed - but I have noticed a problem which I'm now trying to resolve: -

Library calls to parse sentences can sometimes take a little while to return.

The nRF24L01+ transceiver has a three-packet FIFO buffer on input and output.
Its data sheet says "Never allow the FIFO buffers to remain full for more that 4ms."
But they don't say why. I found out why! If the FIFO stays full for over 4 ms the chip simply
stops working completely until a reboot. Not ideal when controlling a big model helicopter!

Because of this, when a library call decides to take >4 ms before returning, all communication
just stops catastrophically.

So my question is: how can I get all these calls to return faster, reliably?

The problem is only very occasional. Sometimes the system will be fine for over three hours
before it fails.

Hoping someone can help!

Malcolm Messiter

Posts: 1
Joined: Fri Jan 14, 2022 1:07 pm

Please be positive and constructive with your questions and comments.