Specifications

Maximum rate a SNAPpy script can toggle a GPIO pin:

11583 Hz

In other words, each True/False cycle took 86.33 µs.

Keep in mind that as a general rule, SNAPpy scripts should not be looping, the above rate is only

attainable if the node is doing nothing else (for example, no radio or serial port communication).

Maximum rate for readAdc() calls:

Maximum 120 samples/second.

NOTE! – This measurement was taken using a script that did not actually do anything with the data.

You will also have to take into consideration any numeric processing required (data thresholding, etc.),

as well as the need to actually store the data someplace.

C Byte Transfer Time

The actual I

C transfers are done using “bit banging” in software. This was measured using a logic

analyzer at 155 µs per byte.

SPI Byte Transfer Time

The actual SPI transfers are done using “bit banging” in software. This was measured using a logic

analyzer at 76 µs per byte.

Virtual Machine Speed

SNAP 2.4 Instructions Per Second (IPS): 51630

Reserved Hardware

The internal 1 KHZ timer (“sysTick”) inside the ARM processor is used to generate the 1 millisecond

time base for SNAP. Hardware timers TIM1 and TIM2 remain available for use (for example, for

generating PWM waveforms).

The PA5 pin if held low at power-on reset forces entry into a serial boot loader built into the chip.

This is a hardware feature of the chip, and cannot be overridden. This does not mean you cannot use

this pin for other purposes, but you definitely should refer to the manufacturer’s data sheets and

reference designs before doing so.

SNAP Reference Manual Document Number 600-0007K Page 201 of 202