Re: [Paparazzi-devel] Soft uart possible?

[antoine drouin]

The SSP port of the LPC2148 is exposed and usualy unused on tinys.
This port is both high troughput and low overhead. A chip such as the
SC16IS752  ( http://www.nxp.com/acrobat/datasheets/SC16IS752_SC16IS762_7.pdf)
could be used to add two hardware uarts. I've drawn the board but
never manufactured it (
http://svn.savannah.gnu.org/viewvc/paparazzi4/trunk/hw/misc/serial_extender.brd?revision=3468&root=paparazzi&view=markup
)
At the moment I am working on designing a board using a STM32 instead
of a LPC2148. The STM32 has 3 uarts

Regards

Poine


On Mon, Sep 14, 2009 at 11:26 AM,  <address@hidden> wrote:
> Hi Timo,
>
> Yes, both hardware UART ports are used on the LPC2148 (for GPS and
> telemetry).
> The only option for a third UART is via software.
>
> I understand that the LPC2148 is 40-60% utilised when running the
> paparazzi code so there is some remaining capacity available. For low
> serial speeds, polling a pin would be sufficient. However for high
> speeds, timers & interrupts would be necessary.
>
> The timer and interrupts associated with the PPM input (pin#30/CAP0.2)
> could be used for software serial input instead. I haven't tried it and
> not sure if anyone else has.
>
> The open-source mikrokopter project has some c code to decode the 115200
> bit/s serial signal from a 2.4 GHz Spektrum satellite receiver at:
> http://svn.mikrokopter.de/mikrowebsvn/filedetails.php?repname=FlightCtrl
> &path=%2Ftags%2FV0.74d%2FSpectrum.c Although based on the ATMega644P
> using a hardware UART, it could be adapted and implemented in the
> Paparazzi system. I haven't tried it and not sure if anyone else has. It
> seems feasible.
>
> The alternative is to use the PPM encoder board
> (http://paparazzi.enac.fr/wiki/Other_Hardware#PPM_Encoder_Board). The
> Spektrum serial signal could be input on the "servo 1" pin (pin#30/RXD)
> which can be configured as hardware serial input. The code could then
> decode the signal and output PPM to the autopilot.
>
> Hope this helps.
>
> Cheers, Mark
>
> -----Original Message-----
> From: address@hidden
> [mailto:address@hidden On
> Behalf Of Timo Drick
> Sent: mercredi, 2. septembre 2009 01:31
> To: address@hidden
> Subject: [Paparazzi-devel] Soft uart possible?
>
> Hi all,
>
> it would be nice to have some more uart ports at the Twog or Tiny v2.
> Did anyone try to implement a soft uart.
> One application would be to read 2.4 Ghz Spektrum receiver data. The
> satalite receiver send serial data with 115 kBaud data rate. Only a RX
> uart pin is needed to read the receiver data. If this works no ppm
> encoder board and only 3 wires are needed.
>
> regards Timo
>
>
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