Custom LPC2148 board issues

Development Boards MicroMod
1

I’m having some issues with an LPC2148-based design, and want to get some feedback before I try replacing the MCU.

I have a custom board with an LPC2148 on it. The layout is based on a number of working layouts (from Sparkfun, Keil, etc). I can post a schematic if anyone would like me to. I used a hot plate to reflow the board, and I followed a normal leaded solder reflow profile as closely as possible. The temperature never got above 220 °C, and I didn’t leave the board on the hot plate to cool. I inspected and fixed all solder joints under a microscope before applying power, and used a DMM to watch the current the first time I powered it on. Current draw looked ok, LDO output looks ok, no magic smoke from any ICs.

Everything looked ok, so I tried connecting to it using a JTAG adapter (SEGGER J-Link). That didn’t work (it didn’t detect anything on the JTAG chain, and it says RTCK doesn’t respond to TCK and that TDO is stuck high). I’ve verified the JTAG pinout, buzzed out all the JTAG connections and everything looks fine. Next, I tried to use ISP. I don’t get any response from the chip for ISP, either.

My final thought was to check the 12 MHz oscillator (Digikey # 478-4359-1-ND, using appropriate loading caps) in case it got damaged during assembly or reflow. I have a Sparkfun Logomatic board, and a DMM shows ~0 V across the oscillator during normal operation and in reset. On my board, a DMM showed 3.3 V (VCC for the system) across the oscillator at all times, and my poor-man’s LSA (an FPGA sampling at 100 MHz with ChipScope running on a laptop) didn’t show any oscillations. I replaced the oscillator, but there’s no change. I’ll check out the oscillator again tomorrow at work using an oscilloscope, but I’m starting to think it may be the LPC2148 itself that’s damaged.

Does anyone see anything I may have missed? Any suggestions before I go order another LPC2148?

Thanks,

Carson

2

The oscillator probably isn’t working, you need a scope to check it properly. Check the User Manual for oscillator design details including feedback capacitor values.

3

Thanks for the fast response, Leon.

I checked with a scope between each side of the crystal and ground, and I’m only seeing DC. XTAL1 (pin 62) is at VCC, while XTAL2 (pin 61) is at ground. While debugging before, I replaced the crystal, and I’m using the appropriate loading caps. I was very careful while soldering the replacement crystal, so I’m confident I didn’t damage it.

I’m definitely thinking now that something is wrong with the LPC2148 itself, but I’d appreciate any other suggestions.

Thanks,

Carson