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gwinstek-gpd: Retry device identification on failure 

Try the identification command up to three times
if the device responds with 'Invalid Character.',
which can happen if the device has buffered part
of a command but not executed it.
This commit is contained in:
Richard Allen 2021-01-16 13:31:31 -06:00 committed by Soeren Apel
parent 10fd326dea
commit c329b788d2
1 changed files with 26 additions and 4 deletions
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30
src/hardware/gwinstek-gpd/api.c
View File

@ -21,6 +21,8 @@
#include <string.h>
#include "protocol.h"
#define IDN_RETRIES 3 /* at least 2 */
static const uint32_t scanopts[] = {
SR_CONF_CONN,
SR_CONF_SERIALCOMM,
@ -117,12 +119,32 @@ static GSList *scan(struct sr_dev_driver *di, GSList *options)
if (serial_open(serial, SERIAL_RDWR) != SR_OK)
return NULL;
gpd_send_cmd(serial, "*IDN?\n");
if (gpd_receive_reply(serial, reply, sizeof(reply)) != SR_OK) {
sr_err("Device did not reply.");
/*
* Problem: we need to clear the GPD receive buffer before we
* can expect it to process commands correctly.
*
* Do not just send a newline, since that may cause it to
* execute a currently buffered command.
*
* Solution: Send identification request a few times.
* The first should corrupt any previous buffered command if present
* and respond with "Invalid Character." or respond directly with
* an identification string starting with "GW INSTEK"
*/
for (i = 0; i<IDN_RETRIES; ++i) {
/* Request the GPD to identify itself */
gpd_send_cmd(serial, "*IDN?\n");
if (gpd_receive_reply(serial, reply, sizeof(reply)) == SR_OK) {
if (0 == strncmp(reply, "GW INSTEK", 9 )) {
break;
}
}
}
if (i == IDN_RETRIES) {
sr_err("Device did not reply to identification request.");
serial_flush(serial);
goto error;
}
serial_flush(serial);
/*
* Returned identification string is for example: