Serial Data Transmission with RF - Improvements

The "pipe-lining" fix in the transmitter was still bugging me.

Fortunately I came up with a solution. With the CPU clock slowed down to 62.5kHz, half what I had been required to use, and NOP instructions in both _TXOn and _TXOff, I achieved the jitter free waveform I was after.

I assume that with enough NOP instructions the pipeline was being forced to reload more often and the jitter caused by random reloading was gone. 

In my first application, a shed door monitor, I expect a single D cell will last over 4 years. The maths suggest 11 years but can an alkaline battery last that long without leaking and self discharge reducing the life?

Briefly,

: _TXon  [ 1 PC_ODR _TxEn ]B!  ;
: _TXoff  [ 0 PC_ODR _TxEn ]B! NOP NOP NOP NOP NOP NOP ; \ 8 bytes 

was changed to

: _TXon  [ 1 PC_ODR _TxEn ]B! NOP NOP NOP NOP ;
: _TXoff  [ 0 PC_ODR _TxEn ]B! NOP NOP NOP NOP ; 

I then used the ]M! command to build up the assembly bytes for a complete On and Off packet without any calls.

Testing Anko CR2032 cells in a Joule Smasher Led Flasher - Update 3

 

It's now been 7 weeks and the Anko CR2032 cells have been a good purchase. As the graph below shows they are holding up well. The peaks and troughs are the result of extreme heat waves here and then cooler days.

It's hard to predict how much longer this cell will last. The best estimate I have is 10 months.

I'll post an update in a few months.

 

Li Ion Battery Charging - Results for Float Charging New LiIon Cell at 8 months

 

Background and Method

More fully explained in this post but briefly I am using a control battery to confirm if any degradation is due to float charging or simply the passage of time and high ambient temperatures. Apart from the time being tested the test battery remains in a CC/CV charger floating at 3.93V. This charges the cell to approximately 70% of capacity then floats at this voltage. The control cell is charged to about 50% capacity before being removed from the charger and stored on the shelf. When the control battery is tested it is fully charged before the test.

Initial Test Results after 8 Months

Having established a base line for the cell capacity when fully charged I have now floated one cell at 3.93V for 8 months with 12 discharge tests during that period.

Looking at the discharge tests of the battery left on float charge at 3.93V there is as yet no meaningful degradation in capacity. The Feb 23rd test followed a scorching record breaking few weeks of summer and can be discounted. 

A full charge of the test battery versus the control battery shows no ill-effects after 8 months. I'm just about done with claims you can't float charge a Li-Ion cell. As yet there is no evidence that a conservative float charge does any damage to a Li-Ion cell.

Testing Anko CR2032 cells in Joule Smasher Led Flasher - Update 2

 It's now been 3 weeks and the Anko CR2032 cells appear to be a good purchase. As the graph below shows they are holding up well. The peaks and troughs are the result of extreme heat waves here and then cooler days.

The worst of the no-name rubbish from Crapbay lasted 21 days. The best Crapbay cell lasted some 5 weeks so I will provide another update in a fortnight.