LPC1517 - ISP via USART not working / suspicious behaviour

[lpcware]

Content originally posted in LPCWare by hlsa on Wed Aug 27 08:26:07 MST 2014
I would like to use the ISP via USART programming functionality of the LPC1517FBD48 device.

Therefore I set ISP0 & ISP1 low. Uart_RX is connected to PIO0_14 (Pin 22). Uart_TX is connected to PIO0_15 (Pin23).
I am using the internal Oscillator.
On the software side I am using FlashMagic PS .Net Rev. 8.18.

Unfortunately communication with the ISP Bootloader does not work.


I made several measurements & tests to avoid that it is just a stupid mistake:
[list]
  [*]I measured ISP0 & ISP1 directly at the device. Both are low at PowerOn. Additionally I am sure that the Software, which I downloaded before via JTag, does not start.
  [*]CRP is disabled.
  [*]I tried the following baudrates: 2400, 4800, 9600, 38400, 57600, 115200. Before changing baudrate, I repowered the device to restart ISP autobaud detection.
  [*]Data from the PC is received on the RX line with the baudrate that I have set before on the PC side. Sending a character manually results in the transfer of the correct character (verified via Oscilloscope).
  [*]The device works properly via JTAG.
  [*]Neither the ISP Pins nor the USART Pins are used by my application. They are only used for ISP.
[/list]

Something which is really strange: I can measure that the device sends something on the TX line to the PC. However, the baudrate is about 1000.

The only idea left is chip errata! Anyone having ISP via USART running on this device?

Best regards,
Holger

[lpcware]

Content originally posted in LPCWare by serge on Tue Oct 14 01:07:01 MST 2014
How did you connect RX and TX to the pc? RX and TX are UART and NOT RS232

[lpcware]

Content originally posted in LPCWare by hlsa on Mon Sep 15 23:37:17 MST 2014
Thank your very much for your reply.

I have again verified the ISP pinning. It is correct:
I have the LQFP48 version and the ISP pins PIO0_4 and PIO0_16 are used. Both pins are pulled low.

Please find the relevant parts of my schematic attached.
For normal operation ISP_0 and ISP_1 are both pulled high via a 20k resistor (R15) to 3.3V.
For ISP operation ISP_0 and ISP_1 are both connected to GND via CON3 before power up (see lower part of the schamtic).
The same circuit is used in another design with the LPC4357, except that there is only one ISP pin.

To test it, I did the following steps:
[list=1]
  [*]Power up with ISP shorted to GND.
  [*]Measure ISP_0 and ISP_1 directly at the MCU -> both are low.
  [*]Start FlashMagic Production .Net V8.18.3612 (see attached screenshot for settings).
  [*]Start command "Read device signature". -> Results in autobaud error (see attached screenshot).
[/list]

To ensure that RX and TX are working correctly, I restarted this procedure and measured U0_RX next to PIO0_14. -> Result: data is coming from the PC with the correct baudrate (9600).
Further I measured U0_RX, where data is transmitted, but extremely slowly (<< 9600 baud/s).

Best regards,
Holger

[lpcware]

Content originally posted in LPCWare by nerd herd on Thu Sep 11 09:52:00 MST 2014
Hello,

For the LPC15xx, the ISP pins differ depending on the package you are using. Judging from your post, it seems you have the LQFP48 version, which means the ISP_0 pin should be PIO0_4 and the ISP_1 pin should be PIO0_16. Can you confirm that this is the correct package and that these are the pins you are externally pulling low?

Also, what have you tried that makes you believe the ISP communication fails? Are you unable to use Flash Magic and "Read Device Signature" after choosing the correct MCU, COM port and a baud rate of 9600?