Thursday, 11 August 2011

Working SMT USB HID device

The ICSP/SOIC chip clip arrived from Farnell today.
They really are excellent for next-day delivery. By UPS courier no less, not just Royal Mail (which can take three or more days to arrive!). If you're prototyping and can't wait for the delivery times from eBay suppliers (or just want to buy from someone with proven customer service) we can't recommend Farnell enough!

Anyway, the clip arrived - it is like a sprung loaded bulldog clip, with each of the fine-pitch pins being taken up to a 0.1" pitch header on the tops of the handles.
Before we could use it we had to make a simple pass-through board for my PICKit2 Clone iCP01 programmer (from The idea is to have a board with five pins that we can push the connector from the programmer onto. The other side of the board will be connected to a length of 5-way IDE cable, which in turn is connected to some 0.1" pitch pin header sockets. The sockets slip over the ends of the "chip clip", connecting the PIC programmer to the appropriate pins on the device.

Following the programmer pinout, we had to identify which wires needed connecting to which pins on the headers on the top of the clip handles.

Here's the whole thing assembled

And here it is, in place and ready to program the chip.

By either good luck or good judgement, the chip was immediately recognised by the PICKit2 programming software, and we were able to download some test firmware onto the device.

All went well and after the programming clip was removed, the device was plugged into the laptop via it's miniature USB socket. The usual bing-bong sound told us that the device had connected properly, and further inspection in Device Manager confirmed that our SMT soldered USB/HID device was indeed working.

The last bit of the puzzle now is to update the firmware so that it matches the new pin layout we used (the pin assignments were changed from the earlier version, to make SMT layout easier)