[Fwd: Re: gta04 / MPU / JTAG]

Andy Green andy at openmoko.com
Thu Apr 17 13:18:50 CEST 2008

Hash: SHA1

Hi Folks -

Allen proposed a MPU variant and Joerg examines integrating it.

http://www.ti.com/lit/gpn/msp430f157  <<=== PDF

Lots of nice features in it.

Forwarded mail from Joerg about considerations to confirm the selected
product is right for us:

| The biggest issue is we only have two "programmable serial units",
| USART0 and 1.  I think we need to use one of these for communication
| with the PC.  And one of them for SPI to motion sensor.
| We also need I2C to PMU :-)  But it is OK we have to use shared bus
| concept on I2C.  So CPU, MPU, PMU / Codec are all on same I2C bus -- it
| supports multimaster nicely.  It forces us to use I2C protocol to
| communicate with the MPU from CPU though, max 400kbps / 40KBytes/sec bulk.

That's where I was thinking along when I wrote last msg to you

| HDQ is also serial protocol but we can do it with timer on high priority
| interrupt and normal GPIO so OK.

Yep bitbang, looking forward to it. Also seen his while asking about
in last msg.

| The 16 GPIO on Port 1 and Port 2 are special because they can make
| interrupts.  We need to keep the MSP430 in very deep sleep most times
| and to wake from interrupt when something happens.  So anything that
| makes an event we might need to react to needs to go on P1 or P2 so we
| can wake the MSP from it.

Also the UARTs / I2C can irq, nearly everything can. And return to sleep
without any thinking... :-)
We will just keep a watchdog tick to do time based tasks. so *everything*
(except power on init) will just be IRQ-handler.

| It can be good if we can run the touchscreen from MSP430 ADC.  Maybe see
| if you can think that through, we need to use GTA01 style external drive
| for X and Y when we measure.  Maybe internal DMA helps there.

Forget DMA, AFAICS the A/D is running while cpu sleeping, and we even
have a
COMPARATOR! :-)) to irq when a certain analog level is detected! That's
great! Resistive TS no issue at all.
OTOH I seen some capacitive TS around those GTA04 modells ?!? Have to ask
Allen what's the plan here...

| Probably also we want to use the internal clock stuff to normally run at
| 1MHz if possible.

Nah, *IF* there's something to do (which _is_ when IRQ), better do it
and go to sleep again *quick*. Walk slowly *only* when walking for leisure
while waiting for something to happen,  what we won't do. Anyway we will
internal DCO for sure, no need to do different. So we _could_ go for 1MHz.

| For LED driver, check and see if we can use the direct drive idea with
| GPIO N-channel driver sinking 10mA or whatever for the LED directly.

Think that's no problem, even may use 15~20mA as it's no AMR and we
don't need
the VOL specs (<0.4V or what) for LEDs.

| Can we think of a cool use for this DMA-capable 12-bit dual DAC?

Need more RAM :-(((

| msp430x167  msp430x168  msp430x169 variants appear to be supported by
| GCC toolchain so it is good
| http://mspgcc.sourceforge.net/manual/c745.html

have a look at it

ps: go to [GTA04] list??? If you think so, please fwd!
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