LPC Microcontrollers中的主题 Re: LPC15xx USB-less ISP

LPC15xx USB-less ISP

lpcware — Wed, 15 Jun 2016 17:04:41 GMT

Content originally posted in LPCWare by EtaPhi on Thu Aug 21 00:54:41 MST 2014
Hello.
I'm new to NXP microcontroller.
I'm developing a board to control a PMSM with FOC algoritm.
My board is going to use a LPC1519JBD64 or LPC1518JDB64 or LPC1517JBD64 according to the computing resources that my final firmware will need.

I wonder what may happen when ISP_0 (PIO1_9) and ISP_1 (PIO1_11) are both pulled up and my firmware signature isn't valid.
LPC15xx datasheet says that in such case, the USB bootloader is run, but these parts have no USB.

Should I provide my board with dip-switches to select USART0 ISP mode (or C_CAN mode) as a safety measure?

I'll really appreciate any suggestion.

EtaPhi

Re: LPC15xx USB-less ISP

lpcware — Wed, 15 Jun 2016 17:04:42 GMT

Content originally posted in LPCWare by starblue on Thu Aug 21 02:26:16 MST 2014
Without USB you probably shouldn't pull up ISP_0 and ISP_1 in the first place. Rather pull down ISP_0 and use ISP_1 to select between CAN and UART (if necessary, otherwise just pull it low/high).

Jürgen

Re: LPC15xx USB-less ISP

lpcware — Wed, 15 Jun 2016 17:04:42 GMT

Content originally posted in LPCWare by LabRat on Thu Aug 21 02:35:51 MST 2014

Quote: EtaPhi
Should I provide my board with dip-switches to select USART0 ISP mode (or C_CAN mode) as a safety measure?

It's helpful to add jumpers to pull down ISP0/1 (to switch to UART) and a pin header (UART0 RXD / UART0 TXD / GND) to connect an UART to USB converter :)

If SWD is failing (or you are flashing an image which is deactivating SWD...) you can use FlashMagic to erase the chip...

Of course you can also use C_CAN (if you add a CAN transceiver), but there's no free Software / Tool to use C_CAN bootloader.

Since USB can be added very easy to your board, it could also be a good idea to use a 1549 during development...

Re: LPC15xx USB-less ISP

lpcware — Wed, 15 Jun 2016 17:04:43 GMT

Content originally posted in LPCWare by EtaPhi on Thu Aug 21 05:41:41 MST 2014
starblue, LabRat, your replies are very helpful for me that I'm discovering LPC micros.

My initial development is going to use a LPCXpresso LPC1549 board, while the first prototype board is being built, so USB isn't a real issue.

It's however an issue for the final application, which is airborne.
Since it's a scientific mission, there is no need to comply with DO-179 regulations, but it's better to agree with their mindset, which may be summoned as: "what doesn't exist, can't broke!".

USB support adds weight and pcb space due to connector, ESD protection devices, etc.
It's almost useless for my application.
If there exists a part without USB (as it exists), I prefer it, because I don't have to provide evidence that a bug my activate that unused feature.

Even if LPC15xx micros are COTS (commercial off-the-shelf) components, a triple redundant system, i.e. three LPC15xx working in parallel, with an appropriate voting logic should be DO-179 compliant (if submitted to a third-party certifying authority).

Airborne devices may experience unexpected resets, which may be due to ionizing particles, EMI etc.
It's therefore better to recover from such events as quick as possible, but ISP bootloader must not interfere with reboots.

This is the reason of my request, which addresses a documentation void.

Regards

EtaPhi