topic Re: LPC55, what pins are active high/low by default in ISP boot mode in LPC Microcontrollers

LPC55, what pins are active high/low by default in ISP boot mode

dav1 — Wed, 20 Apr 2022 13:48:31 GMT

When ISP0 (PIO0_5 pin) is pulled low during cold-boot, the LPC55 enters ISP bootloader

couldn't really find the info in the datasheet or UM11126 pdf

I'd like to know if any of these pins are anything else thatn Hi-Z,
i.e. driven high or low or pu/pd..

Re: LPC55, what pins are active high/low by default in ISP boot mode

EdwinHz — Thu, 21 Apr 2022 20:20:50 GMT

You are correct, there doesn’t seem to be any specific documentation about the state of these pins after the MCU enters ISP mode.

However, my guess is that you can base your answer for the state of each of these serial communication pins, by looking into the initialization that our SDK examples use. This should give you a good idea of the initialization state that the pins go through on ISP mode as well.

I hope this helps,

Edwin.

Re: LPC55, what pins are active high/low by default in ISP boot mode

jay_heng — Fri, 22 Apr 2022 02:00:50 GMT

For UART, The RXD pin will be configured as GPIO, digital mode enabled, pull-up enabled for auto baud function, and keep TXD pin to default state.

When Auto baud is done, then both RXD and TXD pin will be configured to UART function, digital mode enabled, faster Slew rate.

Re: LPC55, what pins are active high/low by default in ISP boot mode

jay_heng — Fri, 22 Apr 2022 02:16:55 GMT

For I2C, all pins will be configured as I2C function, digital mode enabled, Filter disabled.

Re: LPC55, what pins are active high/low by default in ISP boot mode

jay_heng — Fri, 22 Apr 2022 02:33:20 GMT

For SPI, The SSEL, SCK, MOSI pin will be configured as SPI function, digital mode enabled, pull-up enabled, faster Slew rate for detection. and keep MISO pin to default state.

Once detection is done, all pins will be configured as SPI function, digital mode enabled, faster Slew rate

Re: LPC55, what pins are active high/low by default in ISP boot mode

dav1 — Fri, 22 Apr 2022 07:07:25 GMT

hi,

Does this mean that the default behavior with factory fuses and empty flash will enable all peripherals in the automatic probe feature?

ie uart gpio high, spi?

would be great if the datasheet could list ALL gpio's reset and states during boot to avoid the risk of misatakes using say a gpio to enable something that ahould be off default that happens to be pulled up or driven high/low due to the boot loader

Re: LPC55, what pins are active high/low by default in ISP boot mode

jay_heng — Fri, 22 Apr 2022 09:18:15 GMT

Yes,

it is not simple I/O level transition during automatic probe, it will check ping packet (0x5A, 0xA6)