Press-pin connector for in-system programming.

First iteration

First iteration, in which premade four-pin headers are used for the pin contacts, and ribbon cable wires are soldered individually into holes in an upper circuit board. This design works well, but presents many problems in contruction, since ribbon wires are difficult to solder onto the board.

Programming connector (Current Best Version) for t45 with individual pogo pins

Push-pin programmer for tiny45, made with individual pogo pins. One reason to use individual pins rather than multi-pin headers is that the design can be directly modified for tiny44 (or tiny10) without adding more than the one pogo-pin to the inventory. The top board is a standard one-sided milled PCB. The bottom is double the thickness, and can be milled on the circuitbaoard mill. I've defined its dimensions in an Eagle file as well as the top board.

• Materials.
• Pogo pins, Digikey ED1122-ND ($0.30 in quantity).
• Header, Digikey S1011EC-40-ND (already on the fab inventory)
• Clamp material: 0.133" phenolic (garolite) from McMaster Carr, part 6842K61. Nominally 0.125" Equivalent to this would be two FR1 boards, laminated with epoxy. Delrin should also be good.
• Top circuit board. This file defines traces to connect push-pins with a 2x3 header. This 2x3 header is compatible with the usual arrangement of ISP programming pins, so that the customary programmer and ribbon cable can be used. Use a one-sided circuitboard to make this part.



• Eagle File for the top board.
• run traces with usual defaults.
• run holes with 1/64" endmill and 0.4 mm depth (in steps of 0.1 mm) to locate holes. Note that 1/64" endmill cannot drill through the board. Making a "starter" hole 0.4 mm deep creates enough of a depression to center the drill when drilling by hand with the #78 drill.
• run hole pattern with 1/32" endmill, 1.6 mm depth to drill holes for headers.
• run outline with standard defaults, 1/32" endmill.
• Bottom clamp board. This file defines the dimensions for the clamp that fits around the t45 chip. Use 1/8" (3.3 mm) thick material for this part.



The images above show the Eagle board (left) and the clamp part as milled (right.) Actually the part shown on the right has shorter tabs than the part shown on the left and reflects an earlier design. The longer tabs seem to be more succesful in locating the programming connector on the chip and are used in the currently documented design.

• Eagle File that defines the shapes to be cut for the bottom clamp.
• run "legs" with 1/32" endmill using usual PCB outline defaults (total cut depth 1.6 mm).
• run hole pattern with 1/32" endmill, depth = material thickness. (3.3 mm in my case)
• run outlinewith 1/32" endmill, depth = material thickness. (3.3 mm in my case)
• Assembly.
• Drill holes for pins using a small drillpress or a vertically mounted dremel tool. Drill with a #78 drill = .0156". (McMaster Carr Part no. 2901A256) Clean board to prep for solder.
• With copper side up, insert pogo pins into the board, fixed end down, as far as possible. Spring-loaded pins should be facing up. Solder. Use a flush cutter to cut off the pin ends on the non-copper side of board.
• Solder straight header pins into top board.
• Attach the bottom clamp so that the pin sheath is flush with the bottom of the clamp.
• Add glue to fix pins in bottom clamp. Epoxy best, superglue works.
• Mark ground pin locations on each board using a black marker or paint. Attach ribbon cable from programmer in correct orientation.
• Assembled connector should be ready to use. Attach to programmer and press down onto powered chip.



Above, photographs of the top board with pins inserted, the top board with pins and header, and the assembled connector. At bottom, the connector is used to program a t45 chip on a board with no external programming connector.

Design for t45 with rivets (not currently reccommended!)

Push-pin programming connector for t44

• Top circuit board for t44. This file defines traces to connect push-pins with a 2x3 header. This 2x3 header is compatible with the usual arrangement of ISP programming pins, so that the customary programmer and ribbon cable can be used. Use a one-sided circuitboard to make this part.
• Eagle File for the top board.

  

• png image to create traces for the top board.
• png image to create holes for the top board.
• png image to create the outline for the top board.
• Bottom (clamp) board for t44. This file defines the dimensions for the clamp that fits around the t44 chip. Use 1/8" (3.3 mm) thick material for this part.
• Eagle File for the bottom board.

  

• traces for the bottom board.
• holes for the bottom board.
• outline for the bottom board.
• Photos of the assembled programming connector with the tiny44.

Assembly is done as described above for the t45 connector.



On the left, the assembled connector is lowered onto the t44 chip, which is powered through the attached wires. Middle picture shows the black dots to mark ground on the boards. Right picture shows the clamp on the chip, programming with no external components on the board. If the clamp matches the chip dimension well, connector can be maintained in position by friction and does not need to be pressed down while programming.