[#5315] awg test fails to show the generated wave on the oscilloscope
Submitted By: Mingquan Pan
2009-07-06 05:51:44 Close Date
Medium High Assignee:
Closed Fixed In Release:
Found In Release:
BF537 Silicon Revision:
Is this bug repeatable?:
Uboot version or rev.:
Toolchain version or rev.:
App binary format:
Summary: awg test fails to show the generated wave on the oscilloscope
awg test fails to show the generated wave on the oscilloscope.
Build the awg test and run on bf537 stamp board, it can caculate the defined waves but fail to show it on the oscilloscope.
--- Michael Hennerich 2009-07-08 07:03:41
The issue is caused by bfin_spi_giveback() deactivating the SPI SSEL while the
DMA is still running in autobuffer mode.
The whole DMA autobuffer stuff is a pretty bad hack, into the SPI bus driver.
I can add a fix on the branch to make the AWG demo run.
But long term I would like to see that we remove the autobuffer SPI DMA feature
completely from the SPI Bus Driver.
static void bfin_spi_giveback(struct driver_data *drv_data)
/* Not stop spi in autobuffer mode */
if (drv_data->tx_dma != 0xFFFF)
1) remove the autobuffer SPI DMA feature from the Blackfin On-Chip SPI Driver
2) Remove the AWG Demo on trunk
--- Michael Hennerich 2009-07-08 07:13:06
I checked a fix into kernel and awg app.
Can you test again?
--- Robin Getz 2009-07-08 08:03:04
>2) Remove the AWG Demo on trunk
Doesn't the netscope need the same?
I would prefer not to remove drivers. (you would be loosing the DAC driver
--- Mike Frysinger 2009-07-08 21:52:02
how can autobuffer dma with spi really be supported ? it would make it pretty
hard to use multiple spi devices wouldnt it ?
it'd be better if these userspace things merely requested a chunk of data and
worked with that rather than saying "keep giving it to me" ...
--- Mingquan Pan 2009-07-09 03:04:32
I tried the branch head kernel again and the oscilloscope can show picture this
time. But it looks the shown picture doesn't go with the caculated one on the
host machine. The voltage shown is higher than set and the sine wave is
the picture is attached.
--- Michael Hennerich 2009-07-09 04:45:00
>>2) Remove the AWG Demo on trunk
>Doesn't the netscope need the same?
>I would prefer not to remove drivers. (you would be loosing the DAC driver
The netscope doesn't use the autobuffer DMA.
The whole thing is kind of dangerous. In the SPI Bus driver we just leave the
DMA and SPI running and then exit. The next message sent out the SPI Bus will
terminate the current ongoing one.
At least this is the theory. However time showed that every time we test it
during our release testing it is broken by some other bug fixes. I have the
impression that only our testing uses this feature.
I can check the same fix made on the branch also into trunk, if we think the
whole thing is kind of valuable. I personally think it's not. In case someone
wants this kind of functionality he should use the SPORT instead.
--- Michael Hennerich 2009-07-09 04:52:34
Works pretty ok for me.
Check your measurement equipment, connections, etc.
-or maybe your card is damaged.
See my scope captures including measurements attached.
--- Mike Frysinger 2009-07-09 13:23:37
cant we implement the awg demo without autobuffer dma ? i dont have a problem
dropping the autobuffer dma mode since as you say, it isnt how the SPI framework
--- Michael Hennerich 2009-07-09 14:27:39
>cant we implement the awg demo without autobuffer dma ?
Not really - we only calculate and store one period in memory.
The autobuffer DMA feature makes it a periodic continuous wave.
I was thinking about using the generic SPORT driver instead of the SPI Bus
--- Mingquan Pan 2009-07-13 06:28:19
I can see the exactly same wave as yours by using ad5443 on bf533 stamp board.
But as to bf537 stamp board, I tried on 4 boards with the same ad5443, and still
fails to get the normal wave, on some boards vol gets lower to 1mv(defult 0.5v),
on the other boards gets higher to 10v.
--- Mingquan Pan 2009-07-16 05:44:41
I check out clean new source and tried again to find that the awg works right
and give out the right wave as yours on at least 2 bf537 boards. And another
board should has something wrong with the spi port, on which board also fails
with spi net case. So label it as bad and close this bug.
File Name File Type File Size Posted By
rect 1khz 1V.jpg image/jpeg 161112 Michael Hennerich
config.awg application/octet-stream 32687 Mingquan Pan
Image2.png image/png 11852 Mingquan Pan
sine 1khz 1V.jpg image/jpeg 181727 Michael Hennerich