From: David Mosberger-Tang <davidm@egauge.net>
To: Navin Sankar Velliangiri <navin@linumiz.com>
Cc: Jean Delvare <jdelvare@suse.com>,
Guenter Roeck <linux@roeck-us.net>,
linux-hwmon@vger.kernel.org, linux-kernel@vger.kernel.org,
David Mosberger-Tang <davidm@egauge.net>
Subject: [PATCH v2 1/2] hwmon: (sht4x) Fix EREMOTEIO errors
Date: Sat, 20 Nov 2021 20:40:59 +0000 (UTC) [thread overview]
Message-ID: <20211120204053.2299501-1-davidm@egauge.net> (raw)
Per datasheet, SHT4x may need up to 8.2ms for a "high repeatability"
measurement to complete. Attempting to read the result too early
triggers a NAK which then causes an EREMOTEIO error.
This behavior has been confirmed with a logic analyzer while running
the I2C bus at only 40kHz. The low frequency precludes any
signal-integrity issues, which was also confirmed by the absence of
any CRC8 errors. In this configuration, a NAK occurred on any read
that followed the measurement command within less than 8.2ms.
Signed-off-by: David Mosberger-Tang <davidm@egauge.net>
---
drivers/hwmon/sht4x.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/hwmon/sht4x.c b/drivers/hwmon/sht4x.c
index 09c2a0b06444..3415d7a0e0fc 100644
--- a/drivers/hwmon/sht4x.c
+++ b/drivers/hwmon/sht4x.c
@@ -23,7 +23,7 @@
/*
* I2C command delays (in microseconds)
*/
-#define SHT4X_MEAS_DELAY 1000
+#define SHT4X_MEAS_DELAY_HPM 8200 /* see t_MEAS,h in datasheet */
#define SHT4X_DELAY_EXTRA 10000
/*
@@ -90,7 +90,7 @@ static int sht4x_read_values(struct sht4x_data *data)
if (ret < 0)
goto unlock;
- usleep_range(SHT4X_MEAS_DELAY, SHT4X_MEAS_DELAY + SHT4X_DELAY_EXTRA);
+ usleep_range(SHT4X_MEAS_DELAY_HPM, SHT4X_MEAS_DELAY_HPM + SHT4X_DELAY_EXTRA);
ret = i2c_master_recv(client, raw_data, SHT4X_RESPONSE_LENGTH);
if (ret != SHT4X_RESPONSE_LENGTH) {
--
2.25.1
next reply other threads:[~2021-11-20 20:41 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-20 20:40 David Mosberger-Tang [this message]
2021-11-20 20:40 ` [PATCH v2 2/2] hwmon: (sht4x) Add device tree match table and document it David Mosberger-Tang
2021-11-20 21:12 ` Guenter Roeck
2021-11-20 21:36 ` David Mosberger-Tang
2021-11-20 21:51 ` Guenter Roeck
2021-11-21 16:15 ` David Mosberger-Tang
2021-11-20 21:08 ` [PATCH v2 1/2] hwmon: (sht4x) Fix EREMOTEIO errors Guenter Roeck
2021-11-20 21:28 ` [PATCH v3] " David Mosberger-Tang
2021-11-20 21:28 ` David Mosberger-Tang
2021-11-20 22:45 ` Guenter Roeck
2021-11-20 21:55 ` Guenter Roeck
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