If you are reading multiple variables, such as forward and reverse
power, then it becomes a big question of resources on-chip vs resources
off-chip.
For instance, I want to read PA current and reverse power. That's two
analog ports on the nano vs none for an i2c peripheral. If I also want
forward power then it becomes three analog ports vs none for an i2c
peripheral. If I also want PA temperature then it's four analog ports
vs none for an i2c peripheral. Reading multiple analog ports through
the nano muxed ADC doesn't appear to be much faster than doing i2c
reads from peripherals.
tim ab0wr
On Sun, 6 May 2018 22:15:37 -0500
"K9HZ" <bill@...> wrote:
If you are only reading one variable, it¡¯s much better to use the
Nano¡¯s A/D. There is no syncing to do¡ just let it run continuously
and read whats ever in the register.
Dr. William J. Schmidt - K9HZ J68HZ 8P6HK ZF2HZ PJ4/K9HZ VP5/K9HZ
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email: <mailto:bill@...> bill@...
From: [email protected] [mailto:[email protected]] On Behalf Of Jerry
Gaffke via Groups.Io Sent: Sunday, May 6, 2018 9:39 PM
To: [email protected]
Subject: Re: [BITX20] SWR
Here's the datasheet:
Pages 20-23 are of interest.
Looks to me like it is on the order of 10 bytes transferred via the
i2c bus for each ADC read, since we have to switch channels between
reads to choose forward vs reflected power. At 100 khz, that's 10us *
10 * 8bits/byte = 800 us. That's an order of magnitude slower than
reading the Nano's ADC using a an analogRead() call, around 100us.
It is possible to speed the i2c bus up from 100 khz to 400 khz,
But we can speed up the Nano ADC reads by a factor of 5, fiddling
with the ADC clock prescaler.
So using the Nano's ADC is much faster than using this i2c ADC chip
Now if you found a good SPI ADC chip, that might be a different story.
Jerry
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