1
\$\begingroup\$

I want to make a USBasp programmer for myself. I have the schematic. But they used a 10 pin ISP connector, whereas I want to use a 40 pin ZIF socket. How do I change the circuit for this purpose?

I've been using a circuit made on breadboard to load my .hex files, but I use 6 pin ISP. I don't quite understand the functions of the 10 pin ISP. What does the pins do?

\$\endgroup\$
  • \$\begingroup\$ Do I need TxD and RxD for ISP programming? \$\endgroup\$ – Nafis Jul 1 '15 at 5:27
2
\$\begingroup\$

You can replace the 10-pin ISP socket with a 6-pin ISP socket, they are functionally identical.

The original USBASP design brings out an additional 2 signals (the TX and RX pin of the programmer MCU) to normally unused pins of the ISP-10 connector because the USBASP creator planned to add support for access to the target UART for debugging to the firmware, but this was never implemented. You definitely don't need these pins for programming.

I don't think it would be very useful to have these two signals on an ISP-10 header anyway, as most devices with an ISP-10 connector will have these pins connected to ground.

|improve this answer|||||
\$\endgroup\$
1
\$\begingroup\$

The pins do exactly what the MCU datasheet says they do in the "Memory Programming" section. Which means that yes, you need a different pinout per device series. Use the MCU datasheet to decide where each ISP connection needs to be routed.

|improve this answer|||||
\$\endgroup\$
  • \$\begingroup\$ Indeed. And if the chips you need to program are sufficiently distinct in the location of the relevant pins, you may just want to make up target PCB's with a standard 10-pin connector and a target-specific ZIF socket. Or else rig up some fancy mechanical or electrical switch to accommodate the pinout differences. \$\endgroup\$ – Chris Stratton Jul 1 '15 at 3:20

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.