Remote control receiver ver 2014 integrated field test

Remote control receiver, version 2014, which has been went through a whole year of development, is put to the field test with a hobby RC car as a testing platform. The test is successful. When the car is come in very close range of transmitter, it still welly controlled without any issue, which is a great improvement from previous version.

The changes for version 2014 is to replace the previous dsPIC30F6014 microcontroller, with the lower cost PIC16F1716, this sound's like a minor modification, and it turns out not like that, the 16F microcontroller is 8-bit and 33F is 16-bit, which means the computation of all 16 bit variables would takes much more cycle and the maximum clock of 16F is 32MHz which is a lot slower than the 120MHz 30F controller. MCU code have to be speed optimized to make the old algorithm running in the new 16F controller.

The 16F comes with a advantage of having a 8-bit digital to analog converter (DAC) which is handy for controlling the gain of analog variable gain amplifier, in 33F MCU there are no such modules, the old DAC is constructed externally by resister ladder, just messy. 8-bit embedded DAC is nice, however in earlier version of PCB, it is found that the output current of the DAC is insufficient to drive the variable gain amplifier (20mA), as the result an OPAMP buffer is added to boost the current up.

The 10-bits Analog to digital converter (ADC) of 16F MCU is also a downside, when the 30F MCU ADC is 12-bits, the 16F analog sample is 4 times less resolution than 33F, which cause problem when receiving signal level is small, additional input scaling is applied to scale the sample value up so to improve the quantization error in amplitude estimation filtering.

There are some other difficulties such as servo pulse resolution and they have been mostly investigated and overcome.