Why PIO0_1 pin has no external pull-up device ?

[lpcware]

Content originally posted in LPCWare by noritan_org on Tue Feb 09 06:06:50 MST 2010
The LPC111x user manual UM10398 Rev.00.10 says in the page 220

---

Quote:
Pin PIO0_1 that is used as hardware request for ISP requires special attention.
Since PIO0_1 is in high impedance mode after reset, it is important that the user provides
external hardware (a pull-up resistor or other device) to put the pin in a defined state.
Otherwise unintended entry into ISP mode may occur.

---

But the LPCXpresso board has no external component on PIO0_1 pin.

Why is the board is working ?
Someday, sometimes, is ISP invoked ?

[lpcware]

Content originally posted in LPCWare by igorsk on Tue Feb 09 16:10:30 MST 2010
Great board, if only EA didn't have obscene shipping rates on top of VAT.

[lpcware]

Content originally posted in LPCWare by NXP_USA on Tue Feb 09 10:42:31 MST 2010

---

Quote: KTownsend
...As for why the LPCXpresso doesn't have a jumper/button for ISP, the logic seems to have been to make something as minimalistic as possible and just expose all the pins...If you can't solder, though, you're not going to have much fun with it.

---

A great way to get lots of peripherals connected to your LPCXpresso is to plug it into the Embedded Artists LPCXpresso base board. You still have to solder headers on LPCXpresso to do this, but it gains you a USB port, a speaker, a USB-UART port for serial, LEDs, accelerometer, and other I2C/SPI serial peripherals such as I/O expanders and an OLED display. They also have many example projects using those peripherals that you can download from their website after you register your board's serial number.

http://www.embeddedartists.com/lpcxpresso/

-NXP

[lpcware]

Content originally posted in LPCWare by ktownsend on Tue Feb 09 06:59:23 MST 2010
It should default to pull up after reset which is why the board still works. If you want to go into ISP mode, just set it low and reset. As for why the LPCXpresso doesn't have a jumper/button for ISP, the logic seems to have been to make something as minimalistic as possible and just expose all the pins ... though USB would have been nice on the LPC1343.  If you can't solder, though, you're not going to have much fun with it.

Here are two ways you can wire up ISP (see attachments), the first using a simple jumper that you set and then reset, the second allows you to just press a 'Bootloader' button and it will reset the device and hold the ISP pin low long enough to go into ISP mode. I'm using the first in a 1114 board and the second on a 1343 board to make entering the USB bootloader as quick as possible. On the 1343 you need to set 0.3 high to go into the USB bootloader (instead of ISP) ... if 0.3 is low it will go into the classic UART-based ISP mode.

[lpcware]

Content originally posted in LPCWare by rkiryanov on Tue Feb 09 06:31:47 MST 2010

---

Quote: noritan_org
Which information do you believe?

---

Internal pull-up resistor should be good enough for evaluation board. "high impedance" in chapter 17 means "pin configured as input", but this does not contradict with pull-up mode after reset.

[lpcware]

Content originally posted in LPCWare by noritan_org on Tue Feb 09 06:25:29 MST 2010
rkiryanov,

Which information do you believe ?

Chapter 5 says pull-up enabled on reset
Chapter 17 says high impedance mode after reset.

[lpcware]

Content originally posted in LPCWare by rkiryanov on Tue Feb 09 06:14:11 MST 2010
Read user manual, Luke!

Table 66. IOCON_PIO0_1 register (IOCON_PIO0_1, address 0x4004 4010) bit description

reset value for MODE.