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PostPosted: Tue Oct 01, 2013 6:27 am 

Joined: Sat Jul 13, 2013 7:27 pm
Posts: 7
Quote:
We're using OpenTag on a Texas Instruments CC430. Do you know if it is possible to wake the processor from sleep with an RF signal? If so, what function/wakeup should we set to accomplish this? If not, what's the best way to conserve power while remaining vigilant (as you've done with hay tag)?


It is a setup issue. There is not a ton of documentation about the DASH7 spec (apart from the spec itself), and how it stores parameters. Setting default idle behavior at compile time requires editing the default_data.c file that is in each app-code folder, and also making sure that app_config.h has the settings to match. This is really easy if you know what you're doing. If you don't, it can be tricky.

Basically what you want to do is edit the sleep-scan file data. It is a bunch of 4-byte scan items. You will want to set it up to do background scans. Background scans are the type of scans that can be used for asynchronous wakeup. The data elements might look like:

0x10, 0x80, 0x04, 0x00,
...


The first byte is the channel ID. 0x1_ is a 55.5 kbaud channel. 0x2_ is a 200 kbaud channel. The second nibble is the center frequency. 0 is the front of the band, 7 the middle, E the end. F has unpredictable results.

The second byte is the "scan code." bit 7 indicates a background scan, which is a low-power channel "sniff" for an advertising packet. b6:4 are an exponent (EXP). b4:0 is the mantissa. The equation is: (4^EXP)*(MANT+1), except with EXP=0. In that case it is: (4^EXP)*(MANT). There is some overlap in the scan ranges for each EXP value. The units are "ticks" = 1/1024 sec.

Using a scan code = 0x43, thus, will specify a 1 second long foreground scan. Foreground scanning is just listening for packets.

The last two bytes are a 16 bit, big endian, unsigned integer describing the number of ticks until the next scan begins. Scan timing is front-chained. So, if this value is less than the duration of the scan, it will happen immediately.

OTAPI_Tasker module can be used on the other side, to schedule advertising and request sessions.


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