Release Notes¶

CPU_IDLE – Behind the scenes, SNAP was constantly checking the radio and serial ports looking for incoming data to be processed. Starting in this version, if SNAP has checked all of the possible sources of incoming data and found nothing to be processed, it will use the CPU’s built-in “idle” capability to wait for the next interrupt. This reduces the power consumption of SNAP nodes that are not processing a lot of traffic, which can increase battery life. Note that if your SNAP node is being kept busy (for example, your application sends a lot of radio and/or serial traffic) then you will not see much benefit from this enhancement.

type() built-in added to SNAPpy. The ability to tell (at run-time) if a variable was (for example) a String versus an Integer was added to the SNAPpy Virtual Machine. As a quick example of where this can come in handy, the loadNvParam() function can reload a previously saved value, but until now there was no easy way to verify it’s TYPE. You could do “is None” and “is not None” checks before (and you still can) but the type() function is much more versatile.

SNAP now allows you to use different multicast “packet forwarding” settings on the serial port versus the radio. In previous versions of SNAP, NV Parameter 6 controlled which multicast groups were forwarded on both the radio and the serial port. You can still choose to do that, but now there is an additional NV Parameter 78 that when set gives the serial port its own settings, and means that the multicast group bitmask in NV Parameter 6 apply only to packets forwarded over the radio. This allows you to do things like “only forward group 0x0002” packets over the radio, and only forward group 0x0004 over the serial port”. To have NV Parameter 6 control both serial and radio forwarding, let NV Parameter 78 to None.

Includes a “SNIFFER Firmware” build for the ATmega1284RFR2.

PACKET_CRC – similar to the previous RPC_CRC feature introduced in SNAP 2.4.19, the PACKET_CRC feature added an additional software CRC to the radio packets. This was added to address issues with “packet storms” seen out in the field. Like RPC_CRC, enabling PACKET_CRC costs you two bytes of packet space (the additional CRC takes up two bytes). You can enable both CRCs if you wish, but this will cost you 4 bytes of packet space total. Here is how PACKET_CRC differs from RPC_CRC:

I2C_RESTART – Prior to version 2.4.37, SNAP could only work with devices that used the “I2C_START, I2C_STOP, I2C_START, I2C_STOP” hardware handshake sequence for back-to-back commands (for example, an i2cWrite() to specify the data to read, followed by an i2cRead() to capture that data). Some I2C devices instead use a “I2C_START, I2C_RESTART, I2C_STOP” hardware handshake sequence. SNAP version 2.4.37 introduces an optional trailing parameter to the i2cWrite() function. When the optional parameter is provided and its value is True, SNAP will end the i2cWrite() command such that the beginning of an I2C_RESTART is created. The following i2cRead() will complete the I2C_RESTART (instead of generating an I2C_START). When the optional parameter is omitted, or is provided but its value is False, then the normal I2C_STOP sequence is generated. This enhancement allows SNAP to work with a wider range of I2C device.

SNAP has always had a “line mode” for HOOK_STDIN, but if you received too many characters before the receipt of a Carriage Return or Line Feed character, the system would print an error message and discard the data. Now even if you have specified “line mode” which technically means “don’t send the data until you get a CR or LF” the system will push what it has received so far if the buffer fills up. This makes the feature more useful. To support this new behavior, an new getStat() option has been added, getStat(18). By calling this function, your SNAPpy script can check and see why the HOOK_STDIN handler has been called.

The SM220 was the first SNAP Module to boast two onboard antennas – a “meandering F” and a “U.FL” connector. Support for software controlled antenna selection was added in this version (refer to NV Parameter 64).

The hardware inside the ATMEL radios includes “trim capacitors” that can be selectively enabled. You can now specify an alternate radio trim setting via an NV Parameter (#63 – NV_ALT_RADIO_TRIM_ID) to take advantage of this hardware capability. Most customers will never need to use this, but if for some reason your units are running higher in frequency then you can change this NV Parameter from its default value of 0 to enable 1-15 steps of additional capacitance (which will lower the radio frequency). The hardware does not have the ability to adjust the frequency in the other direction. (You cannot use the internal trim to raise the frequency.)

Sleep mode 2 (sleep(2, ticks)) added. This new sleep mode uses the “MAC Symbol Counter” inside the radio as a timebase, and provides finer-grained sleep durations.

The “moveable I2C” feature was back-ported from the STM32W108xB version of SNAP. Now if you need to connect an I2C peripheral to a different pair of pins, just specify the alternate SCL and SDA pins in the i2cInit() function call. These two new parameters are optional, you do not have to change your existing scripts unless you want to leverage this new capability. Calling the i2cInit() function without the new optional parameters causes the original pin assignments to be used.