LPC84x ISP

[rolfeigenheer]

The LPC824 in our existing layout has not enough flash memory for our growing application. After sucessfully porting the code to the pin compatible LPC844M201JHI33 we cannot do the In-System-Programming in our production line. 

For unexplainable reasons the RxD and TxD lines for ISP have changed. The FAIM defaults to PIO0_24/PIO0_25. But these pins are not accessible for our production tool. We provided contact pads for PIO0_0/PIO0_4.

I2C pads are also accessible, but the UM (rev 1.6) page 17 says that the ISP is configured for USART. 

So I cannot change the FAIM word without having access to the device and I cannot access the device without changing the FAIM word.

If it is required to access the device through PIO0_24/PIO0_25 to change the ISP interface - what is this useful for ?

Or in other words: If I have access through PIO0_24/PIO0_25 - why should I change the ISP interface ?

This FAIM feature only makes sense if I can order controllers with customized FAIM values. How can I order controllers 

with a FAIM configuration to use PIO0_0/PIO0_4 in ISP (as it was in the LPC82x) ? 

Thanks

Rolf

[victorjimenez]

Hello Rolf,

Actually, if have enough pins to use, usually pins 0_24,0_25 work as ISP UART, because they are only GPIO pin and locate together. But LPC824 is a shrink version, for TSSOP20 package, it doesn't have pins 0_24,0_25, so have to find other pins to work as ISP UART.

Till now, there isn't a variant of the LPC844 with values in FAIM which correspond with the LPC824 and seems no plan to do it.

You can take a look to our paid support MCU programming center. Here you can submit a request to see how much will it cost to change the values of the FAIM before sending the MCUs. However, if your project volume is not huge this alternative will cost a lot. The best and economical option is to build a new revision of your board.

Hope it helps!

Victor.

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[rolfeigenheer]

Hi Victor

LPC824 is not a shrink version. It is available in the same package and has the same fixed pins as 84x. This can’t be the reason to change pin assignment.

Please excuse me that I want to understand. Maybe I’m using it the wrong way. So I need to know how the FAIM bootloader configuration feature is intended to be used. Someone spent time on it to implement and added a autodetection feature which would automatically switch between USART, SPI and I2C. The manual says that autodetection is enabled when FAIM is corrupted. But someone decided to explicitly disable this. Why ? Does it not work ?

Br

Rolf

[victorjimenez]

Hello Rolf,

The LPC824 and the LPC844 both come in the package HVQFN33. However, as I mentioned in before the LPC824 also comes in the package TSSOP20, please see image below. 

This package doesn't have pins P0_24 and P0_25. Due to this, the UART ISP pins were moved to P0_0 and P0_4. This way all the LPC824 family no matter the package they all use the same pins for UART ISP. 

Regarding your other questions:

But someone decided to explicitly disable this. Why ? Does it not work ?

Nobody disabled this characteristic. As you said the autodetection is only enabled when FAIM content is invalid, if you reference table 5 in the user manual, you will see that the default value for the FAIM content valid bits is 11 which corresponds to FAIM content value.   

If you have a valid content value, then you will go to select the ISP interface which the default value is 0 that corresponds to USART0 ISP. Please refer to the following flowchart to clarify this idea.

Regards,

Victor.