4370 slower than 1769

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by JoeE on Sat May 31 04:29:13 MST 2014
in my application (polyphonic synthesizer) I configured a timer to generate an interrupt every 20 µsec (50 kHz). The interupt service routine calls a subroutine doing plenty of calculations and transferring a value via SSP1(at 4 MHz) to an external 12 bit DAC. As I needed more speed I switched from an LPCxpresso 1769  board running at 120 MHz to an LPC-Link 2 board running a lpc4370 at 204 MHz. However the 4370-board is significantly slower. The interrupt service routine takes 9 µsec on the 1769 whereas it takes 22 µsec on the 4370. I determined this by toggling a GPIO-pin at the begin and the end of the interrupt service routine and measuring the pulse length with a scope (and a period counter). Does anybody have an explanation for this behaviour. I am using the LPCXpresso IDE and in case of the 4370 board LPCOpen. The code for the Interrupt service routine ist the same. The code optimization level is also the same in both cases.