Jürgen Lambrecht <[EMAIL PROTECTED]> writes: > Hello, > > The current implementation of HAL_ARM_AT91_GPIO_GET in > hal/arm/at91/../var_io.h uses the AT91_PIO_PDSR register. > But, "Reading the I/O line levels requires the clock of the PIO > Controller to be enabled". So if you forget to enable the related PIO > clock, this HAL_ARM_AT91_GPIO_GET always fails! > Therefore, I propose to use the AT91_PIO_ODSR register. > Anyhow, the added value of PDSR over ODSR is small I think: > -with ODSR you read the value you want this pin to be > -with PDSR you read the actual (physical) value of this pin > They are only different if there is a hardware problem..
Without reading the documentaion: the ODSR give you the contents of the output latch, while PDSR reads the line value. ODSR and PDSR should agree for output pins, but for inputs the ODSR may differ from the line level, since it is no longer connected to the pin and pin is being driven to its current level by some external device. Also, surely if you are using a GPIO port you should be enabling its clock. I would consider not doing that a programming error. -- Nick Garnett eCos Kernel Architect eCosCentric Limited http://www.eCosCentric.com The eCos experts Barnwell House, Barnwell Drive, Cambridge, UK. Tel: +44 1223 245571 Registered in England and Wales: Reg No: 4422071
