topic LPC812 SW in LPC Microcontrollers

LPC812 SW

lpcware — Wed, 15 Jun 2016 20:03:10 GMT

Content originally posted in LPCWare by trimarco232 on Tue Apr 28 05:11:19 MST 2015
Hi,

I have 2 question about the LPC812, but they probably general for the LPC world

I want to program and debug it with my segger debugger (cheap educational) and coocox IDE, I think It will be possible ?

I have red that, in this case, the reset an the Isp pins have to be pulled up. Ok, but I want to use the ISP pin in order to drive a led in running mode : is this possible, without the risk of entering accidentally the bootloader mode when the pin is configured as output and driven low ?

thanks

Re: LPC812 SW

lpcware — Wed, 15 Jun 2016 20:03:11 GMT

Content originally posted in LPCWare by nerd herd on Tue Apr 28 07:51:47 MST 2015
Hi trimarco232,

Having the software select the ISP pin as a GPIO outputting low, and then asserting a reset should not cause the MCU to enter ISP mode since the IO states are not retained when a reset is asserted. Is it absolutely necessary for you to add circuitry around the ISP pin?

Re: LPC812 SW

lpcware — Wed, 15 Jun 2016 20:03:12 GMT

Content originally posted in LPCWare by trimarco232 on Tue Apr 28 13:02:34 MST 2015
Hi nerd herd !
Thank you

Quote:
Is it absolutely necessary for you to add circuitry around the ISP pin?

of course : I have no more room on my pcb and no more pins to source the 20mA for a big LED.

my idea is to connect the anode to VDD and cathode to the pin. The LED is switched on by driving the pin low. So, if a reset occurs by a power-up, the GPIO/ISP pin stays pulled up through the LED, and the chip doesn't enter in running mode. Is this the solution ?