Hi Peter,
Am 18.02.2013 13:54, schrieb Peter Stuge:
> Peter Henn wrote:
>> A patched libusb allow me to setup also latency timer values of 0 for
>> the FT2232H chip.
>
> Please tell more about this patch?
>
sorry, I used the wrong name. It was libftdi, which is only used by the
ft2232 driver and no longer by the ftdi driver. So that could be
applied to libftdi-0.20:
FTDI-2232H and FTDI-4232H USB High Speed devices allow latency timer
values of 0 ms.
Setting this values allow a short package Bulk read latest for the next
USB micro frame on
an USB 2.0 Bus or every 125 us.
--- a/src/ftdi.c
+++ b/src/ftdi.c
@@ -1822,8 +1822,8 @@
{
unsigned short usb_val;
- if (latency < 1)
- ftdi_error_return(-1, "latency out of range. Only valid for
1-255");
+ if (latency < 0)
+ ftdi_error_return(-1, "latency out of range. Only valid for
0-255");
if (ftdi == NULL || ftdi->usb_dev == NULL)
ftdi_error_return(-3, "USB device unavailable");
>
>> Here the updated and used patch for my measurements:
>> --- a/src/jtag/drivers/mpsse.c
>> +++ b/src/jtag/drivers/mpsse.c
>> @@ -305,7 +305,7 @@
>> }
>>
>> err = libusb_control_transfer(ctx->usb_dev, FTDI_DEVICE_OUT_REQTYPE,
>> - SIO_SET_LATENCY_TIMER_REQUEST, 255, ctx->index,
>> NULL, 0,
>> + SIO_SET_LATENCY_TIMER_REQUEST, 2, ctx->index, NULL,
>> 0,
>> ctx->usb_write_timeout);
>> if (err < 0) {
>> LOG_ERROR("unable to set latency timer: %d", err);
>
> Do you suggest the above for inclusion to the mpsse.c code?
No. Using the 255ms latency timer would show now clearly that a send
immediate commad does not work as expected.
>
>
> //Peter
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