Bootloader Hardware Modification

[NavMicroSystems]

Many of you are using a BootLoader with a standard BootLoader Hardware (Loader Cable with MAX232)

You may have realised that this cable can't be used for serial communication with other devices.
(i.e. PIC to PC Communication using HyperTerm)

The Reason is: MCLR on the PIC is pulled permanently LOW by the external device. (DTR on the DB9)

A small modification on the BootLoader Hardware makes Life a lot easier.

The attached schematic shows the standard BootLoader Hardware and the required modification.

(Replace the 100 Ohms Resistor with a 10uF Tantalum Capacitor)

see schematic:

[NavMicroSystems]

There is yet another modification that might be of interest:

If you have a MAX232 on your board, wired as in the BootLoader example, there is one spare driver.

If there is any device on your board that requires a negative (supply) Voltage
(i.e. LCDs with extended temperature range need a negative "contrast" voltage)

Pull T2IN (Pin10) of the MAX232 HIGH and T2OUT (Pin7) will provide that negative voltage.

rgds