I have added 2 crystal oscillators, one on xtal1 xtal2 and one on rtxc1 rtxc2 also I have added 4 capacitors one 2 on the first pair and 2 to the second pair. I have connected the jtag the closest possible to the core(processor) to avoid using resistors. I have also added a 2 pin power supply for a ionbattery from sparkfun.
My current problem is that I want to create a reset circuit and I don’t know how to do it. I have seen several versions of reset circuits for this processor. Could you point me to the right direction? Also do I have to use resistors anywhere?
PS. If you really want me to stop using this forum help me build this pcb and I will delete my account.
Lots of problems! Route the supply and ground tracks first, with wide tracks. You need decoupling capacitors for each pair of supply and ground leads. Avoid all those acute angles.
Jtag connections on “red” layer are very badly routed. As you already have 2 layers and vias, use them to make straight connections.
“Blue” layer is mainly for ground signals. Make it a complete ground layer. Connections to GND pins, capacitors and connectors will be much simpler. It will aslo help agains EMI problems.
Do you have the schematics? Judging from the PCB I am pretty sure that your caps are connected in series with the voltage pins, but I can’t be sure until I see the schematics.
The Vdd and Vss pins of microcontroller should be connected to their respective power supply.
Go to Olimex website and look around for their boards, documentation and schematics.
My personal own Polux’s 2 cents: if the exercise is to design,route, make and solder a pcb, no problem. But you will discover that making a pcb which is working and complete on first iteration could be often very difficult.
But if the exercise is to have a LPC2138 running to learn microcontroller programming, you should buy something existing.
Pull-ups on /RESET and P0.14, decoupling caps should be parralel instead of in series. Only the 3.3V pins need decoupling, the ground pins don’t. But seriously, start with an existing board, write software for that, and if that works then start designing hardware for it.
http://www.olimex.com/dev/pdf/ARM/LPC/L … ematic.pdf look at this schematic u can see that there is a resistor right there where crystal oscillator is. On the lpc2138 user manual on the crystal oscillator connection there is no resistor… What shall I do?
Don’t underestimate me :P. I have achieved more difficult things compared to my knowledge level and I have understand that
the best way to learn is to start from hard things. Step by step will get you boring! Exciting is when every post in this forum is
a vital piece of information.
ON topic:
What are you talking about there is clearly a resistor on the RTCX2 connection. Take a look at this. DOes this look more parallel to you?
Note: On the grnd pins I have removed the capacitors because as I have noticed in the schematic their not needed on every connection, and it makes sense in a way. I want the battery to get discharged smoothly, it doesn’t interact in anyway with the micro-controller.
With parallel I mean electrically parallel, not geometrically parallel. The power pins should be connected directly to the power source and near each power pin a capacitor should be connected between power and ground.
on the olimex development board there is just one on the final grnd output? Why I should use more? DOesn’t make sense. Aren’t the capacitors used so that the battery gets discharged smoothly so that the battery can give me a smooth current?
