Tell me more ×
Electrical Engineering Stack Exchange is a question and answer site for electronics and electrical engineering professionals, students, and enthusiasts. It's 100% free, no registration required.
up vote 5 down vote favorite
1

The various LPC microcontroller chips have a boot mode that accepts serial communication and writes the received program to Flash. I want to make a PCB with and LPC1114 that must be programmed in circuit, with only minimal interface circuitry on the PCB. Is there a standard connector for supplying the required signals (GND, RxD, TxD, Reset, BootModeEnable)?

share|improve this question
2  
There are standard connectors for JTAG and SWD, but there is no standard connector for program loading via a serial connection. – Leon Heller Apr 24 '12 at 19:15
For lack of a standard, is there some connector that is often used? Or even a single board that has such a connector?? – Wouter van Ooijen Apr 24 '12 at 19:21
Just use a header with three pins - Gnd, Tx and Rx. – Leon Heller Apr 24 '12 at 20:22
For 'hands off' one or two extra pins are needed: reset and BootModeEnable (could be combined at the cost of some extra circuitry). – Wouter van Ooijen Apr 25 '12 at 6:40

5 Answers

up vote 1 down vote

I use Sparkfun's USB to UART board. I bring out UART0, reset and isp to headers. I connect reset and isp to ground with jumpers, then use FlashMagic. This only seems to work right if I also power the device from USB, so the grounds are common.

Sparkfun's board:

https://www.sparkfun.com/products/718

share|improve this answer
You don't need to take power from usb to establish common ground, it is enough to tie the grounds together. – Chris Stratton Mar 12 at 1:13
up vote 1 down vote

If you set up a connector to be compatible with the header version of a low voltage FTDI USB serial cable, you have the option of not needing to contract for the manufacture of custom cables.

You can drive the boot mode off a status line and couple the reset to that with a cap (think I might have used a transistor as an inverter when I did this with an ST part). Then deselecting and reselecting the boot mode will reset the chip and prepare it for download.

share|improve this answer
I considered that approach, but I'd rather stick to the more or less standard two-handshake-lines-approach. That leaves the option open to command a non-bootload reset, and saves a few components on the target board. – Wouter van Ooijen Dec 21 '12 at 15:02
up vote 0 down vote

I did not work with LPC1114 before but take a look at the below address. On the left, you will see a link to a schematic file...

http://www.keil.com/mcb1000/

share|improve this answer
This board has the serial interface hardware (in this case: max232 chip, but could be an FT232RL or something else) on the PCB, so there is no connector that carries the signals I want to interface. – Wouter van Ooijen Apr 24 '12 at 18:21
On the second page, there is the JTAG interface. You have to use a JTAG adapter on the PC side, but on the PCB, there is no additional hardware like RS232... – Malkocoglu Apr 24 '12 at 18:34
I want to use the serial interface, not JTAG. Too complicated, too much signal lines. – Wouter van Ooijen Apr 24 '12 at 18:45
SWD only requires two or three signals. You get debugging, which is very useful. – Leon Heller Apr 24 '12 at 19:19
2  
True, but at the cost of a more complex interface at the PC side. (And I seldom use a debugger, even if I have one available) – Wouter van Ooijen Apr 24 '12 at 19:22
up vote 0 down vote

Im actually building something with the same micro. I just picked up one of these: http://ics.nxp.com/lpcxpresso/ for ~$20 from digikey, cut off the "target" side of the board, and wired up a custom connector on the "LPC link" side to work with my programming header. The CodeRed made environment is annoying since its Eclipse based (I loathe Eclipse) but it works in Windows, Linux, and maybe Mac. They have instructions for all of the command line programs to work with the LPC Link interface.

I have an environment set up in linux to just run make dl and it will initialize the link, program it, and enable security bits, all via USB and the SWD connections to the LCP1114. Can even be used for debug provided that you don't reuse one of the SWD signals.

It isn't serial like you are looking for, but it works like a charm.

share|improve this answer
1  
I know the lpcexpresso's, I have 1114, 1343, 1769 and the baseboard. Nice stuff (although I ditched both the IDE and the LPC link in disgust), but not suited for what I want. My PCB will be 20 x 50 mm max. – Wouter van Ooijen Apr 24 '12 at 19:54
@WoutervanOoijen, I use vim and have all of the tools set up to run via command line. My board is a bit bigger but it should work just the same. In past when I have done small projects like that I made the programming pins come out to largish pads, and then rig up a custom jig to connect those up via spring loaded pins and hold it in place. I don't really know of any off the shelf solutions for a "common/standard" connector to connect to your PCB. – Kris Bahnsen Apr 24 '12 at 20:52
up vote 0 down vote

If you want serial programming with the standard connector (meaning RS232) why don't you implement normal UART (MAX3232 or something) with standard DB9 male connect on the LPC side? Than you simply use the extender (male to female) DB9 cable towards PC (or use serial to usb cable if you PC does not have serial port). In any case, put a female DB9 on your PLC board, and you never ever have to manufacture your serial cable :-). Don't forget to wire pins properly, extender cables are straight (1-1, 2-2, ... 9-9).

If the space on the board was issue (not enough room for DB9) then you can provide 2 x 5 pin header only.

Of course, you could also use spare MAX3232 level shifters to force your board into reset / boot mode like I did on my NXP/AT89C51Rx2 based board also using Flashmagic. Same principle, teh Falshmagic takes control over the boot entry via serial line.

All that said, I would go with SWD / JTAG and had debugging at my disposal.

share|improve this answer

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

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