Programming external devices
With the JTAG header it is possible to program external devices. It is a cheaper to use a board with only microcontroller than using a complete Simplecortex in a project, once the project is finished no debugger is needed anymore.
Before you can program an external device the microcontroller on the Simplecortex needs to switched off.On the Simplecortex there's the dip-switch B4 alias DB-EX (that is how it is called in the I/O list). Switch DB-EX (Debugger Extern) has a simple function, it only interrupts the supply of the microcontroller.
Warning! Connect the JTAG cable the right way or it will cause a short circuit.
The picture below shows a visual diagram:
It is possible to program all the microcontrollers which are supported by CoIDE but note that the libraries for the Simplecortex are only compatible with the LPC17xx family. In the future we will write libraries for the LPC11xx microcontrollers. These are cheaper and still good enough for 90% of all the projects.
For this example we used a cheaper model of the LPC1769. This microcontroller is also from the LPC17xx family but it has some limitations. To make your own project only the microcontroller, powersupply and programming header are needed. All the unconnected I/O can be used although it is wise to check the datasheet first. Every pin with the discription Px[x] can be used as I/O. Most of the pins are internally connected to a periphcerals like I2C, SPE, etc. There are also 4 led’s and two buttons connected to the microcontroller. Obviously they can be removed but they are very handy for experimentation.
To keep the powersupply low-cost, NX1117 voltage regulators are used. The 3.3v supply is secured with a PTC (resettable fuse) of 500mA. The upper connector is the JTAG connector. It´s important to keep the pin-layout the same. This pin-layout is use by a lot of debuggers, for excample: J-link, U-link. Connectors JP1 – JP4 are exactly the same connected as the Simplecortex.