Standard ISP Header

A discussion on the LPC2000 Yahoo group about the In System Programming facility on Philips chips led to the idea of choosing a common standard for a header to interface with the chip for programming.

The ISP function requires 3.3v logic levels for serial transmit, receive, reset (active low), and the P0.14 line that enables the boot loader when held low for a few ms after a reset.

This can be wired up to a PC RS232 port, with appropriate level shifting. For those who don't want to include an RS232/line driver in their board, it makes sense to have a little header where one can plug in a small adapter that has the line drivers for connection to a PC.

We've tentatively (after much discussion) agreed upon using a 0.1" male header of 8 pins in two rows, with the following layout (when viewed from above):

1	3.3V	/RST	2
3	/ISP	RxD	4
5	0v	TxD	6
7	n/c	key	8

The 'key' is a missing pin on the header - and a corresponding filled in hole in the female plug, to make sure one cannot insert it wrongly and unleash the magic smoke from within one's circuit.

Notes:

• All at 3.3v logic levels
• /ISP is P0.14 on the LPC21xx chips
• The board with the uC on is expected to have pull ups on /ISP and /RST so the thing will work fine without anything plugged into the header
• The 3.3v and 0v lines are supplied by the uC board, and are intended for powering the RS232 line drivers.
• RxD is receive from the perspective of the uC device - the programmer should drive this line, and the uC should drive the TxD line.

An adapter that conforms to this interface and provides a link to a PC's serial port is available from Aeolus Development http://www.aeolusdevelopment.com/Articles/InSystemProgramming.html Also has interface schematics for Philips LPC2104/5/6, LPC2119/29 and Analog Devices ADuC7020/21.