CAN P87C592 PCB Corrections

8031 timeline

CAN pinout mess

Quick fix board

A PCB error? What, again? I’m afraid so. This time the board was four layers with four boards made, so it was not a cheap mistake. The pinout on the CAD package for this device was either labelled from the corner or mid-way along the top edge. Whatever it was, it was different to the actual device. The little indent on the chip confirmed this when they arrived. There were no local through-hole board manufacturers, so a quick two sided board was made with as much as possible on the bottom side. It was not going to be possible to take a ribbon cable to all the pins; the crystal might complain! The ugly fix with a RS-232 buffer for testing to a PC host is shown to the left.

Target Surgery

The surgery on the board used ribbon cable to attach to the surface mount pads. Ribbon cable is not a good soldering candidate as the insulation was never made to take any heat. Anyway, the board could be tested, but at the cost and still not prepared to shell out for a 8051 C compiler, this was my last 8051 project. Hopefully forever, particularly when seven years later, an ARM processor sold for a dollar (Luminary Micro LM101) which included Flash, JTAG debug, etc, at a lower price than previous RS-485 buffers.

CPU board pinout mess

Limited appeal

CAN was not revisited due to the prices of protocol analyzers and our preference for distributed I/O would be local control with Ethernet connecting nodes. The requests for CAN also never materialised for the projects we were involved in.

Future Prospects

We did look into the CAN kits from Luminary Micro, however, we can no longer spend time on remote I/O without decent interface boards. Cypress Semi and other were considered, but if we do revisit distributed I/O, it will use local processing power on some low-cost ARM core. We will post some proposals and documentation on local alarming, trending, debouncing etc., distributed I/O and some of the previous interface boards as part of the documentation side. For a first pass, see here