I have designed a system which has 1 receiver & up to 4 transmitters. using the sleep timer & PM2 to sleep for 200mS & wake to check for transmissions. If a packet is detected, then the receiver remains awake to process the data, then sleeps again & the cycle is repeated. This works well with good battery life & good range. This is now in mass production with ~6000 units in operation.
I've since designed an enhanced system based on the original design & firmware with some extra feature for a 2nd product. Again similar battery life & range. This has just had the 1st production run of 1000 receivers & 4000 transmitters of which is sold out. Recently I've received 3 receivers back with the same symptoms. They appear to the locking up. I have a unit here which works fine.
On close investigation the are not waking from sleep reliably. When I look at the external oscillator on the good unit I can see the clock start, stay awake ~12mS, then good to sleep again for about 190mS. In the faulty units I we this, but I sometimes see the clock stay active much longer & occasionally it's continuous & occasionally the nothing. This becomes unresponsive & sometimes & have to reinstall the battery to get is working again
I have followed Design Note DN106 (SWRA162B) & I believe I've implemented it correctly. I also did not see this occur on the 1st product, or the pre-production units of the 2nd product. I can only think there are a race condition which I'm missing that only creates a problem on a handful on devices.
Please can I send you my code to check & possibly one of the faulty units to ensure they are not faulty.
This is quite urgent so your prompt response would be greatly appreciated.
John Galvin