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scpi_usbtmc_libusb: Retry if a Bulk-IN request starts with an empty packet 

This seems to make the Rigol DS1054Z work.  It's still a bit janky --
on a live capture, sample 688 (zero-based) out of the 1200-sample
frame seems to consistently contain garbage.  I'm not sure what's
going on.
This commit is contained in:
Andy Lutomirski 2020-06-13 15:39:17 -07:00 committed by Uwe Hermann
parent e2283318c1
commit 025bd56f10
1 changed files with 28 additions and 11 deletions
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39
src/scpi/scpi_usbtmc_libusb.c
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@ -524,19 +524,36 @@ static int scpi_usbtmc_bulkin_start(struct scpi_usbtmc_libusb *uscpi,
uint8_t *transfer_attributes)
{
struct sr_usb_dev_inst *usb = uscpi->usb;
int ret, transferred, message_size;
int ret, transferred, message_size, tries;
ret = libusb_bulk_transfer(usb->devhdl, uscpi->bulk_in_ep, data, size,
&transferred, TRANSFER_TIMEOUT);
if (ret < 0) {
sr_err("USBTMC bulk in transfer error: %s.",
libusb_error_name(ret));
return SR_ERR;
}
for (tries = 0; ; tries++) {
ret = libusb_bulk_transfer(usb->devhdl, uscpi->bulk_in_ep, data,
size, &transferred,
TRANSFER_TIMEOUT);
if (ret < 0) {
sr_err("USBTMC bulk in transfer error: %s.",
libusb_error_name(ret));
return SR_ERR;
}
if (transferred < USBTMC_BULK_HEADER_SIZE) {
sr_err("USBTMC bulk in returned too little data: %d/%d bytes\n", transferred, size);
return SR_ERR;
if (transferred == 0 && tries < 1) {
/*
* The DEV_DEP_MSG_IN message is empty, and the TMC
* spec says it should at least contain a header.
* The Rigol DS1054Z seems to do this sometimes, and
* it follows up with a valid message. Give the device
* one more chance to send a header.
*/
sr_warn("USBTMC bulk in start was empty; retrying\n");
continue;
}
if (transferred < USBTMC_BULK_HEADER_SIZE) {
sr_err("USBTMC bulk in returned too little data: %d/%d bytes\n", transferred, size);
return SR_ERR;
}
break;
}
if (usbtmc_bulk_in_header_read(data, msg_id, uscpi->bTag, &message_size,