Started assembling the board tonight. I decided to build 2 boards so I 'll have some form of comparison when something doesn't work...
First I placed the three ICs and the micro USB connector.
First IC is the PIC18 microcontroller that manages the system. It is the hardest to solder as it comes in a TSSOP fine pitch package. My eyes and hands are still pretty steady and I still manage to solder these parts with little problem. This little Micro has built in USB that we use to upload new firmware and configuration. Other that that it has all the necessary functions to implement a DC brushed controller - hardware PWM, Analog to digital converter, internal EEPROM to save the ESC configuration after power down.
Second IC is the current amplifier. This amplifier serves two purposes, one is to amplify the motor current by 20 and the second is to filter the PWM switching noise before being sampled by the MCU's analog to digital converter. The filter is a second order sallen-key low pass filter that is fixed at about 2kHz (our PWM frequency is just above 11kHz). This gives very good compromise between switching noise and sampling bandwidth. "Too much" filtering will make current limiting very slow and lazy - "Too little" filtering will make the samples very noisy and the MCU will have to work harder in order to average them.
The third IC is the MOSFET driver. This driver can drive the MOSFET gates at up to 3 amps and does the level shifting needed (5V microcontroller IO to 12V MOSFET gate).
Total Soldering time around 10 minutes.
Next I assembled all the resistors. This took around 1 hour due to the fact I was missing one resistor value and had to go 5 times through the Digikey order to find it. Found it stuck to another plastic bag...
I hope I find some time tomorrow to continue. That's all for now.