[YARDStick] questions

[Michael Ossmann]

Cinead,

Sorry your email was stuck waiting for moderation for a few days.  I
meant for this list to be unmoderated, but I had the default setting
wrong.  I fixed that today.

See my replies below.

On Sat, Mar 12, 2016 at 09:53:53PM -0800, Cinaed Simson wrote:
> 
> Hi - when I plug my yardstick into the USB, no LEDs light up.
> 
> When I receive a signal using rfcat, I see a green LED light up.
> 
> When I transmit, no LEDs are lit.
> 
> Is this normal?

Yes, that is normal behavior.  This is becoming a frequently asked
question, so I started a FAQ:

https://github.com/greatscottgadgets/yardstick/wiki/Frequently-Asked-Questions

The best ways to check that the YS1 is powered on and operating on the
USB port are lsusb, dmesg, or simply starting up rfcat and seeing if a
dongle is detected.

We may want to change this behavior and configure one of the LEDs to
always illuminate when the device is powered on, or perhaps it should
turn on only after USB configuration is successful.  RfCat firmware
originally assumed that there was only one LED on a dongle, but we have
three on YS1.

What do people think about the following behavior?

LED1: USB configured (should always be on)
LED2: RX active
LED3: TX active

or this?

LED1: USB configured (should always be on)
LED2: RX/TX active (currently the behavior of LED1)
LED3: amplifier active

Or perhaps we should leave LED1 unchanged so it behaves the same as the
LED on all other RfCat dongles.

By the way, the colors are:

LED1: green
LED2: red
LED3: yellow

> What is the maximum transmitting power of the yardstick in mW?

Roughly it is 100 mW (20 dBm).  The transmit power is reduced a bit as
the frequency increases, and it may vary from unit to unit.  It is
approximately 20 dBm at 300 MHz, 19 dBm at 450 MHz, and 18 dBm at 900
MHz.  (Those numbers are with the TX amplifier enabled.)

> Is the RF gain 0 or maximum like the HackRF?

Yes, the RX and TX amplifiers (the ones not built into the CC1111) are
either on or off.  Variable gain stages are available within the CC1111.

> How accurate is the frequency - does it drift?

The frequency stability of the crystal is specified at 20 ppm, so that
is how much variability you can expect over the normal operating
temperature range.

Mike