Modernize Harmony 880

One alpha PCB has been fully wired up and fitted with the front cover of the remote.  LCD fit-up well and tested.  The back light LEDs seem to do pretty well but the region by the d-pad underlit, almost like I forgot to go back and finish that section.  All of the dome switches seem to be aligned well, but haven't started any software testing on MSP430 for the button scanning.

The bare LCD screens and 4mm dome contacts arrived from Aliexpress.  The LCD screens are right size and match the footprint for the alpha board.  They are thinner than the stock screen so mounting with some foam adhesive looks like the best route for installation.

I stuck a few of the dome switches on the alpha board to test things out.  They give a nice solid click but the fiddly-ness of installing these has been confirmed.  When the case is fully snapped shut, some of the buttons stopped working.  I thought it was an alignment issue at first but looks like the alpha PCB is twice as thick as the stock PCB (1.6mm vs 0.8mm).

Still haven't soldered up a test board yet.  I just added a diode laser cutter to the work shop and was hoping to get it setup to cut stencils from mylar.  This became a project in itself clearing a spot in the workshop, building a stand and enclosure, and running ventilation.  Cutting the stencils out is still a work in progress.

Alpha revision of the PCB was placed on order 7/4 at 8:42p.  Order was delivered 7/8 at 5:15p.  A little less than 4 whole days for production and shipment!  This was 22^nd PCB order I’ve placed with JLCPCB and had the most complex board outline by far.  The PCB fit in the case pretty well, the only fitment issue was along the sides of the screen where the button pads were real close to the board outline.  I intentionally traced it a bit bigger in this region for clearance to the button pads.  There are a few plastic ribs inside the case that are real tight but should fit nicely with some hand filing/sanding.  The narrow little notches on the sides had me concerned, but these didn’t seem to slow JLCPCB down at all.  The copper layer around the reverse mount LED holes appears to have been shrunk down a bit for clearance to the hole but otherwise the boards look just like the KiCad renderings. The mounting pad for the mini USB connector went right to the board edge.  I was going to remove the connectors from the stock PCB to test on the alpha board.  The case has some ribs around the battery holder region that are going to interfere with the reverse mount LEDs.  Final design might need to shift position of these LEDs or require a bit of modification to the case.  Once the parts on the back of the PCB are populated, I’ll try to transfer the tape layer with the button domes to the alpha board.  All the pads line up with the EL tape cutouts I removed but manually getting 53 4mm domes in place and secured seems like a pretty fiddly process.

Alpha PCB design has been completed to test the major aspects of the layout: screen mounting, buttons, case fit, battery contacts.  MSP430 micro controller was installed on the PCB with all the connections to the button matrix for testing.  A bunch of test points were created for interfacing the PCB with a ESP32 dev board.  This allowed the board to get done and ordered without working out the connection between ESP32 and MSP430.

I found the bare LCB module used in the waveshare 2" screen on ali-express.  I ordered 5 of them but shipping will take a month.  I broke the ribbon cable on the first screen during disassembly.

The board outline was pretty jagged and intricate.  Also had copper pretty close to the reverse mount LED holes.  We'll see how well JLCPCB handles the fabrication.  5 boards were $8 USD.

Scanned board on scanner glass.  Imported image into Fusion360 to scale and trace features.  Exported DXF file to import into Kicad. 

Factory PCB uses snap action dome contacts held in place with tape.  Replicated same foot print.  Kicad design has the button matrix and mounting holes so far.

TODO list for test fit PCB:  Screen footprint, ESP32, MSP430, charging base connector, usb connector, battery connector.

The orders have arrived.  3 remotes and 2 charging bases.  The most beat-up remote was taken apart to inspect.  While reuse of all the existing electronics would maximize recycled content, the effort to re-design will be a lot less than effort to re-engineer the internals.

The waveshare 2.0 inch TFT screen is a perfect size for replacement.  Need to find a way to remove from the carrier PCB without damage.

The existing remote looks to have used EL tape for the keypad back lights.  This looks like a good opportunity for reverse mount LEDs.

ESP32 will be used for replacement processor with a MSP430 dedicated for keypad matrix scanning.  Time to start on a PCB to test button, LED, and screen fitment in the case.

There were quite a few listings for Harmony 880 remotes.  Most were in the $15 to $40 range.  I ordered 3 that were cheap and looked in good shape.