Axel Thimm wrote:
Is this true? The firmware is 14KB, that would be a rate of less than
3KB/sec or 23739 bits/sec. Isn't that too low for a 100KHz i2c
transmission? Theoretically the tranferrate should be more like 10-12
KB/sec
Yes, ideally you could get 12KB/s out of 100KHz. The bit-shift
algorithm used to send the bits however has some overhead. (This
information is from linux-2.6.8-24.14 i2c-algo-bit.c)
For every bit sent:
setSDA
udelay
sclHI (set and wait for SCL to go hi)
udelay
setSCL(0)
udelay
For every byte sent:
sdaHI
udelay
sclHI
udelay
getSDA
sclLO
udelay
So for every bit, there's minimum 3 * udelay, and for every byte an
additional 3 * udelay. This makes byte transmission speed at best ((3 *
8) + 3) * udelay or 25 udelay = 25us. 1 / 0.025s = 40 bytes/s max.
ivtv is using i2c_master_send on the whole image, does anyone know if
i2c_master_send framents the block into too many small messages? That
could explain the delay. Alternatively perhaps the comuptation of
fw->size in request_firmware is wrong?
i2c_master_send just calls the i2c-algo-bit sendbytes() with the
entire 1000 byte buffer, which is then transmitted as above without
being fragmented. fw->size appears to be accurate too. I think
everything is going as planned.
I contaced Hauppauge engineering and asked about this. This was done
in older code and was abandonded due to problems (I have no
information about the nature of the problems).
I've dug through the their driver code from pvr150_inf.zip,
hcwpp2.sys (dated 2004/10/6) and this is the only firmware upload
routine that exists (to the best of my disassembly knowledge, which is
pretty good). The "Win-TV PVR Update" pvr150_22_22292.exe does not
contain an updated hcwpp2.sys at all. Are they sure they abandoned it?
I don't have a windows box I can check driver versions on, but I'm
resonably certain I'm looking at the right driver.
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