There are like… 4 vdd and 4 vss which ones am I supposed to connect? Some are called vdda some other vssa… I cant really understand… Vss is ground and Vdd is power right? Also what should be the current?
They must all be connected, and each pair must be decoupled. The a denotes that it is an analogue supply.
Current depends on the speed and application.
If I am given a voltage limit than the current limit should be known if the resistor of the bus is known. However with what information do I need to provide you to know what the current should be? Did you also meant that each Vdd must be connected separated to a voltage source and the same for the GND?
edit: By decoupling u mean to add a capacitor right? On both GND and Vdd, but how do I know what capacitor I should purchase?
Current consumption can be estimated from the information in the data sheet.
100 nF, close to the leads, with wide tracks.
leon_heller:
Current consumption can be estimated from the information in the data sheet.100 nF, close to the leads, with wide tracks.
When will you be online to skype to check the image of my board because wide tracks and how close the capacitor to the source is, is something relative…
Is my board any good? I have done decoupling, I have shorten the tracks of the jtag… What else do I need to add?
Decoupling capacitors should be very close to the chip, with power and ground distributed by wide tracks.
how closer? Than I won’t be able to use any other of the pins… and if I make the gnd tracks wider they will overlap the other simple tracks. Please provide with an example…
As close as possible, < 5 mm.
d4n1s:
Is my board any good? I have done decoupling, I have shorten the tracks of the jtag… What else do I need to add?
You will need to use SMD capacitors, because you can’t get much closer with the through-holes you are using. Also don’t you need a crystal?
what is a crystal?
A crystal oscillator, a piece that generates the clock for you uC to operate on. If I recall correctly the LPC213x series does not have an internal oscillator, so you need an external crystal.
You need a pull-up on the /RESET pin. On the LPC214x there is another pin you need a pull-up on, or it will only go into ISP mode. I’m sure that the other LPC2xxx also have such a pin; look it up in the data sheet.
On the KEIL development board there are also pull-ups on the JTAG pins, but I’m not sure if they are mandatory.
I think that the pull ups and pull downs on that board u are reffering is because the jtag is too far from the core, in the datasheet it is said that the max length of a track to jtag should not be over 3cm and if it is over 5cm to do something (I dont remember what exactly) However I think that my jtag is closer than 3cm…
Also what kind of resistors am I using for pull ups(If I am not mistaken of the terminology pull ups means increase current). How am I going to find the ohms that it should have?
Also I haven’t ever used a crystal oscillator again, could you tell me what values it should have?
Perhaps you should try designing something much simpler, using a PIC or AVR.
not strong enough to interface with cmos camera and it is part of a school project which, if I finish would give me a huge grade.
I have also purchased the arm and jtag so I am not up to spending another 20$ or so… Any other ideas?
edit: I just done the changes u told me… is this any better? is it going to work?
Look at some of the designs in the LPC2000 Yahoo group files section.
Also, study the chip documentation in detail.
The documentations lack of information, the current the processor should run with is not included. DO I also have to power up all Vdds? Also I don’t have access to LPC grp files, could you please paste some photos here? Thx!!! And take a look at my prev post which I edit to include my edited board. Tell me what it is missing.
Join the group!
All supply and ground pins must be connected and decoupled close to the chip.
All the information you need is in the documentation. There is a lot of it - the data sheet and the user manual.
Is there a reason why you using ARM7 rather than a ARM Cortex-M3? The CM3 chips are much easier to route. Internal PLL, usually shared Vdd and AVdd pins, no external VddCore supply needed. Performance can be greater than the ARM7 and cheaper. I had to use boardhouses to create ARM7 designs due to the complexity of the power and JTAG routing, but I can do a CM3 chip on one of my homemade single sided boards with just a few jumpers.
Anyway, with ARM7 there is usually VDD, which is digital power, 3.3V. AVDD, which is analog power, 3.3V. VDDCore, which is the core power, 1.8V. Some of the chips have an internal regulator for the 1.8V that exits to an external pin, you are forced to route it from one pin to the others. All the Vdd pins should have 100nf decoupling caps as close to the pins as possible. Further input conditioning is dependent on how clean your power supply is and how clean you need the analog power, which is used with the ADC’s.
Really, no different than any other microcontroller, just more of it.
ARM’s web site implores people to not use ARM7 in any new designs.
Not that old, but microprocessors in the ARM world move at a fast pace, and so says ARM, at the 10 billion Quantity.
Quoting ARM’s web site
ARM7 Processor Family
ARM7 Processor Family Image
Note: The ARM7 processor family (ARM7TDMI(S) and ARM7EJ-S) is not recommended for new designs.
Introduced in 1994, the ARM7™ processor family has been immensely successful, and has helped establish ARM as the architecture of choice in the digital world. Over the years, more than 10 billion ARM7 processor family-based devices have powered a wide variety of cost and power-sensitive applications.
While the ARM7 processor family continues to be used today for simple 32-bit devices, newer embedded designs are increasingly making use of latest ARM processors such as the Cortex™-M0 and Cortex-M3 processors, both of which offer significant technical enhancements over the ARM7 family.
But there are still a lot of ARM7 boards for sale, ready to use.