Wireless BLE Kinesis Advantage (Custom Controller)

Soldered everything down and everything is functionally perfect. 

Only minor issue is I forgot to remove "i2C Pullups" from the board silkscreen but other than that, the boards are good to go.

I actually still have 4 spare since the first one worked perfectly. Let me know if you'd like one!

I also reduced the delay from 17 to 10 as I getting a few typos (could be just because it's 3am). Still, 9/10 = 90% sleep is not bad!

just got these in the mail, time to get soldering! 

So everything went as planned, using SPI the whole loop executes in under 1ms (compared to 8ms with i2C at 400kHz). I didn't even have to set the SPI speed, the default for the nrf52 was plenty fast.

Next, I added delay(17) at the end of the loop, so the CPU get's to sleep for 17/18 = 94.4% of the time! That alone brought the idle (not typing) current down to around 2mA. This should extend battery life considerably as it was hovering around 7-8mA before.The only negative to SPI is that since it uses an extra pin, I've had to go back to using TX/RX pins for led(s). 

2 mA is already pretty good but I since I was back at this project again, I might as well try get it lower.

Turned off some functions that weren't going to be used and lowered bluetooth power since the keyboard is always going to be close to the computer.

  NRF_UARTE0->ENABLE = 0;  //disable UART
  NRF_TWIM1 ->ENABLE = 0; //disable TWI Master
  NRF_TWIS1 ->ENABLE = 0; //disable TWI Slave
  NRF_NFCT->TASKS_DISABLE = 1; //disable NFC, confirm this is the right way

// and lowered bluetooth power from -4 to -8
Bluefruit.setTxPower(-8);

aaand it went down to 1.6mA! Might not seem like much but that's a 20% reduction in power consumption.

I'm pretty happy with that, if we were only running the board without any LED(s) on a 3,000mah that would be (0.7 * 3000/1.6) / 24 = 54.7 days continuously! If we factored in that the board would at most be used 8 - 12 hours continuously (without a single break of 15 mins). That's over 100 days of battery life. cool.

I've finished routing the new V3 board and sent it to the manufacturers (PCBgogo) again since they were plenty fast and the boards worked perfectly. Only difference is now that I know it works, I decided to splurge on Matte Black with gold immersion.

I've been using the board for a while now and it's been relatively stable but I'm still not 100% satisfied with the power consumption of around 5mA. Currently the board runs for about 12-18 days on a 3,000mah lipo depending on usage.

I could just remove all the LED(s) and call it a day but that really feels like a step back so instead I'm going to switch over to the much faster SPI MCP23s17 chip which should let us run through the loop 10 times faster at 0.8ms. We can then sleep (delay) for 9ms and still have debouncing at an acceptable (no input lag) of 20ms. Theoretically this would mean our CPU can sleep for 92% of the time and only be active for 8% which should hopefully get the idle current down to 1-2mA and increase battery life to at least a month.

I'm estimating 10-14 days for parts and to finalize the new board designs so if anybody's wanting to give this project a go, definitely wait a little bit longer for the improved boards.