Arduino with 8Mhz crystal oscillator.

hello,
I am currently searching for an Arduino board which already has a mounted 8Mhz crystal oscillator?

The 3.3V Arduino Pro Mini is running off a 8MHz crystal I believe

Arduino Pro Mini

Less than $3 from ebay, if you can afford to wait. pro mini 3.3v

dawn98f:
I am currently searching for an Arduino board which already has a mounted 8Mhz crystal oscillator?

There are the 8Mhz Pro Minis, but I have only seen them with resonators fitted.

Not seen an 8Mhz Pro Mini with a crystal, let alone one with a mounted crystal oscillator ...........

Why do you need\want one with a crystal oscillator ?

I suspect anything with a 32U4 (as USB timing is quite critical); the only one I'm aware of is the SparkFun ProMicro 3.3.V/8MHz but I don't know every board on the market.

sterretje:
as USB timing is quite critical

Is it really? Judging by the use of USB interface chips without crystals, I thought it was anything but!

Why do you want 8Mhz ? Really only needed if you want to run at lower voltages ??

What chips beside FT232 run without an external crystal?

It has

Internal 12MHz Oscillator - The Internal 12MHz Oscillator cell generates a 12MHz reference clock. This provides an input to the x4 Clock Multiplier function. The 12MHz Oscillator is also used as the reference clock for the SIE, USB Protocol Engine and UART FIFO controller blocks.
Clock Multiplier / Divider. The Clock Multiplier / Divider takes the 12MHz input from the Internal Oscillator function and generates the 48MHz, 24MHz, 12MHz and 6MHz reference clock signals. The 48Mz clock reference is used by the USB DPLL and the Baud Rate Generator blocks.

Baud Rate Generator - The Baud Rate Generator provides a 16x clock input to the UART Controller from the 48MHz reference clock. It consists of a 14 bit pre-scaler and 3 register bits which provide fine tuning of the baud rate (used to divide by a number plus a fraction or “sub-integer”). This determines the baud rate of the UART, which is programmable from 183 baud to 3 Mbaud.
The FT232R supports all standard baud rates and non-standard baud rates from 183 Baud up to 3 Mbaud. Achievable non-standard baud rates are calculated as follows -
Baud Rate = 3000000 / (n + x)
where „n‟ can be any integer between 2 and 16,384 ( = 214 ) and „x’ can be a sub-integer of the value 0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, or 0.875. When n = 1, x = 0, i.e. baud rate divisors with values between 1 and 2 are not possible.
This gives achievable baud rates in the range 183.1 baud to 3,000,000 baud. When a non-standard baud rate is required simply pass the required baud rate value to the driver as normal, and the FTDI driver will calculate the required divisor, and set the baud rate. See FTDI application note AN232B-05 on the FTDI website (www.ftdichip.com) for more details.

Thank you all for such quick reply.
I need that 8Mhz crystal because i need to generate 10ns delay.

Paul__B:
Is it really? Judging by the use of USB interface chips without crystals, I thought it was anything but!

All the boards that I have seen have a crystal for the USB. I admit that I haven't seen many :wink:

dawn98f:
I need that 8Mhz crystal because i need to generate 10ns delay.

10 nanoseconds?
Not going to happen with an 8Mhz clock.
Leo..

dawn98f:
I need that 8Mhz crystal because i need to generate 10ns delay.

So you probably need a CPU that can be clocked it 100Mhz............