Friday, July 27, 2007

RTC on the PXA270

In order to get DTN working properly in the future we need to have RTC setup and working on the gumstix. Jeremy and I at first thought that we could simply attach a backup battery to the V_BACKUP pin on the power control chip. We tried that and had 3V coming out on the V_RTC pin, but still the RTC would reset on every power down/restart. Then we thought it may be in software, so I looked through the driver code and commented out the line that resets the clock if the status register is misbehaving. The resets still persisted. Finally, I found out that on the PXA270 the RTC is on the chip and in order to keep the oscillator running we'd need to power the whole chip (at least keep it in deep sleep mode) and keep RAM alive. We decided to order an external RTC board, which is a DS1307 board which has I2C interface. Gumstix already has the patches for these boards and it should be pretty easy to get them setup once they come in and just set the PXA RTC to the external RTC.

Also, I've started to look at the CLA code for DTN2 and I'm still trying to figure out whether DTN sends out the bundles or if the CL has to do that. I should be able to understand that pretty soon. Ideally, I'll be able to simply notify DTN2 of link changes and have it handle message delivery. All the discovery can already be done by OLSR anyway.

1 comment:

NovceGuru said...

Stupid blog spam ^

I am very interested in how things are coming along with the external RTC, thanks.