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Jan 19, 2013, 02:26 AM
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Chip radios

So you wanna get wireless digital video from the smallest package.

The MRF49XA/SI4421 have been the workhorses for the last 4 years. They send 256kbit at 1mW.

In 2010, the MRF89XA came out. It sends 200kbit at 30mW & has a bigger package.

$parkfun has had the nRFL01+ since 2009. It sends 2Mbit at 1mW. It doesn't have a baseband pin like the MRF's, so getting 2Mbit requires a lot of CPU time.

All the RC products use Cypress. Nothing from Cypress or TI has a baseband pin, but there are single chip options for over 1Mbit.

The $10 ML2730 has baseband pins, 2Mbit, & puts out 100mW. 4 of those might be a useful position sensing solution for $40. It could handle video & not have the dropout problems or latency of wifi.

That's about it, in the chip radio department. The fake test pilot's 2009 decision to go with the MRF49XA was driven by the need to avoid analog 2.4Ghz video interference & cost, but now that digital video is the priority, the ML2730 may be the chip of choice.

The baseband pin potentially allows distance to be measured & allows data to be sent with much less CPU time. Just connect the baseband pin to the UART instead of banging on SPI registers. The 256kbit chips would probably only resolve distance to several meters but a 2Mbit chip might do the job, indoors.

256kbit would probably send a compressed 160x120 JPEG at 1 frame every 4 revolutions. 2Mbit would do each revolution. 160x120 is about the highest useful resolution when the current camera is on a monocopter. The wifi & bluetooth solutions are all heavier & interfere with I2C.

dBm is a very confusing metric. We all know how far 100mW can go, but not 15dBm. The easiest way to convert dBm to practical experience is the 2nd digit being the number of 0's. 0dBm = 1mW 10dBm = 10mW 20dBm = 100mW 30dBm = 1000mW
Last edited by Jack Crossfire; Jan 19, 2013 at 04:38 PM.
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