The 5387 board, since V4, has used two 32-bit quadrature encoder counter chips to support the four incremental encoder ports. These parts are obsolete and we have no source for them any longer.

We have found a source for the 12-bit version of these chips. It is apparently a custom build of the 12-bit version that is housed in the 32-bit package. This allows us to use the chip without a board layout change. The only issue is that we have to modify our software to use the 12-bit version. We have to read the encoder often enough so that we never see more than 2048 counts between reads or our math will not work properly to calculate the change between reads.

Through empirical testing we have determined the Max Encoder rate to be 2MHz. If we read the encoder every 100usec, that calculates out to a maximum number of counts equal to 200 per read, well below the 2048 limit.

There will be a new limitation introduced. Any 5387 board with the new 12-bit chip will no longer be compatible with older software versions. The cutoff will be V4.110.0 and V5.110.0. Any software older than this will be incompatible with 5387 boards containing the new chip. Software versions newer than these will work with either version of the chip.

On the old chip we have a Bogus encoder count read of 10,0000 per read. We will be lowering that threshold to 2000 counts per read.

We have modified the Closed Loop Controller code to read at 100usec, even when there are no Open Loop Targets.

The OL gets similar treatment but with a much simpiler change since it was already written to read the encoder more than once per sample.