Caveat Emptor – SOIC8/SOP8 test clips

My mistake may benefit you if you are into budget surface mount PCB creation.

I recently purchased an 8-pin  test clip for SOP8/SOIC8 surface mounted chips. My goal was to use my USBasp programmer to flash in-circuit ATTINY85-20SU chips. I hastily, too hastily, purchased a Chinese SOIC8/SOP8 test clip similar to the shown in Figure 1, below.  This was a mistake and I am largely to fault, although the minimal documentation provided by the eBay seller didn’t help. In any case, closer examination of the photo would have convinced me that it wouldn’t do what I wanted – at least not easily.

Fig. 1: Chinese SOIC8/SOP8 Test Clip.

The only way that I could use this test clip as delivered would be to insert the included header PCB into a breadboard, also find a way to plug my USBasp programmer into the breadboard (not so easy without a second header PCB) and use jumper wires to connect the two in a usable way. I didn’t want such a kluge and decided to try and salvage what I could from what was delivered.

There were three problems: (1) The 10-pin IDC ribbon connector is wired straight through, i.e., IDC connector pin 1  to test clip pin 1, IDC connector pin 2  to test clip pin 2, etc. The ATTINY85-20SU is not wired that way; (2) the ribbon cable has two wires cut off right by the IDC ribbon connector and I needed pin 9 (MISO); (3) the ribbon cable is soldered to the pins on the test clip and sealed with shrink-wrap, making replacement with a new cable difficult.

First, I soldered and removed the existing cable and then, using a scrounged 10-wire ribbon cable, I soldered and shrink-wrapped the new cable to the test clip with the wires in the correct places. I also put a larger piece of shrink wrap around the wire nest to try and make it a bit less fragile. Fragility is my concern because my scrounged ribbon cable had solid, not stranded, wire.

In any case, it works. Figure 2 shows my completed OIC8/SOP8 test clip just after I finished flashing the ATTINY85-20SU on the little purple PCB.

BTW – these OIC8/SOP8 test clips are available on eBay all by themselves in case you’d like to inexpensively do your own OIC8/SOP8 in-circuit programming. The clip itself is decently made and does the job. It makes good pin connections and grips the chip firmly with little plastic teeth. It is not a Pomona 5250 but it also is not 20+ dollars.

Fig. 2:  Reworked SOIC8/SOP8 Test Clip for In-Circuit Programming

P.S.: Look carefully at my purple PCB and you’ll notice that I’ve shorted the ATTINY85-20SU’s pins 7 & 8 to fix my design error. I laid out this board in about 30-minutes (I forget what my rush was) and ran Vcc to pin 7 instead of 8, where it belonged.