Hi ben!
I am Midas from Belgium and I love your show!
I am thirteen years old and I love working with the arduino uno.
I have just a question about the arduino.
In several shows you talked about to "embedd" an arduino.
I have done this a few times with a crystal and 2 22 pF capacitors.
But in your episode abou the Xbox coin reward system I didn't see any capacitors.
Are these capacitors REALLY needed or can you leave them away?
Thank you for reading my question, I hope to hear from you soon.
If you are using a crystal, you really should use those caps. From an atmel datasheet
When using resonators with the Atmel
AVR, it is necessary to apply (external)
capacitors according to the requirements of the facilitated resonator. A parallel
resonator will not be able to oscillate stable if the capacitive load applied is
insufficient. If the capacitive load is too high the oscillation may have problems
starting due to drive level dependency of the load. The trick is therefore to find an
appropriate value for the capacitive load. The value to look for in the data sheet of the
crystal is CL, the recommended capacitive load of the resonator (viewed from the
terminals of the resonator). The capacitive load, CL, of the oscillator circuit, including
stray capacitances and the capacitances of the XTAL pins of the AVR can be
determined empirically or it can be estimated by Equation 5-1.
5.3 Recommended capacitor values
The recommendations here will work well in most applications, but there is no way to
provide general values for the external capacitors that can be guaranteed to work with
all resonators.
When using the clock option “ext. crystal oscillator”, crystals with a nominal frequency
from 400kHz and up can be used. For these standard “high” frequency crystals the
recommended capacitor value is in the range 22-33pF.
Many AVR's include an onboard internal oscillator, usually 8Mhz, those can be used and you won't need a crystal at all. Just make sure to set your fuse bits.
If you are using a crystal, you really should use those caps. From an atmel datasheet
When using resonators with the AtmelAVR, it is necessary to apply (external)
capacitors according to the requirements of the facilitated resonator. A parallel
resonator will not be able to oscillate stable if the capacitive load applied is
insufficient. If the capacitive load is too high the oscillation may have problems
starting due to drive level dependency of the load. The trick is therefore to find an
appropriate value for the capacitive load. The value to look for in the data sheet of the
crystal is CL, the recommended capacitive load of the resonator (viewed from the
terminals of the resonator). The capacitive load, CL, of the oscillator circuit, including
stray capacitances and the capacitances of the XTAL pins of the AVR can be
determined empirically or it can be estimated by Equation 5-1.
5.3 Recommended capacitor values
The recommendations here will work well in most applications, but there is no way to
provide general values for the external capacitors that can be guaranteed to work with
all resonators.
When using the clock option “ext. crystal oscillator”, crystals with a nominal frequency
from 400kHz and up can be used. For these standard “high” frequency crystals the
recommended capacitor value is in the range 22-33pF.
Many AVR's include an onboard internal oscillator, usually 8Mhz, those can be used and you won't need a crystal at all. Just make sure to set your fuse bits.
