[PATCH v2 0/2] iio: adc: ti-ads1298: add ADS1298/ADS1299 driver

[PATCH v2 0/2] iio: adc: ti-ads1298: add ADS1298/ADS1299 driver

[Md Shofiqul Islam]

The ADS1299 is an 8-channel, 24-bit SPI ADC from Texas Instruments
designed for EEG and biopotential measurement. It shares the same SPI
interface and register map as the ADS1298 ECG ADC family, differing in
PGA gain range (24x vs 12x) and internal reference voltage (always 2.4V).

This series adds ADS1299 support to the existing ti-ads1298 driver by
extending the channel configuration and adding the compatible string to
the device tree binding.

Changes in v2:
- Remove ads1299-4 and ads1299-6 variants; only ads1299 (8-channel)
  is supported. The -4 and -6 variants have not been tested on hardware
  and their channel-count difference is better handled at runtime via
  the ID register rather than separate compatibles.
- Remove second DT binding example (ads1299 node); one example is
  sufficient per binding documentation guidelines.
- Simplify vref-supply description; remove ADS1298 vs ADS1299 specifics
  that belong in the datasheet rather than the binding.

Md Shofiqul Islam (2):
  dt-bindings: iio: adc: ti,ads1298: add ADS1299 EEG ADC variants
  iio: adc: ti-ads1298: add ADS1299 EEG ADC family support

 .../bindings/iio/adc/ti,ads1298.yaml          | 15 ++--
 drivers/iio/adc/ti-ads1298.c                  | 84 ++++++++++++++-----
 2 files changed, 75 insertions(+), 24 deletions(-)

-- 
2.51.1

[PATCH v2 1/2] dt-bindings: iio: adc: ti,ads1298: add ADS1299 EEG ADC variants

[Md Shofiqul Islam]

The ADS1299, ADS1299-4, and ADS1299-6 share the same SPI interface
and register map as the ADS1298 ECG ADC family but are designed for
EEG and biopotential measurement.  Key differences from ADS1298:
- PGA gain up to 24x (vs 12x for ADS1298)
- Internal reference is always 2.4V (no 4V option)

Add compatible strings and update the vref-supply description to
document the ADS1299 reference voltage behaviour.

Signed-off-by: Md Shofiqul Islam <shofiqtest@gmail.com>
---
 .../devicetree/bindings/iio/adc/ti,ads1298.yaml   | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml b/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml
index 71f9f9b745cbc..202776cee73ff 100644
--- a/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml
+++ b/Documentation/devicetree/bindings/iio/adc/ti,ads1298.yaml
@@ -4,11 +4,15 @@
 $id: http://devicetree.org/schemas/iio/adc/ti,ads1298.yaml#
 $schema: http://devicetree.org/meta-schemas/core.yaml#
 
-title: Texas Instruments' ads1298 medical ADC chips
+title: Texas Instruments ADS1298/ADS1299 biopotential ADC chips
 
 description: |
-  Datasheet at: https://www.ti.com/product/ADS1298
-  Bindings for this chip aren't complete.
+  ADS1298/ADS1298R: 8-channel, 24-bit ECG ADC. Max 12x PGA gain.
+  Datasheet: https://www.ti.com/product/ADS1298
+
+  ADS1299: 4/6/8-channel, 24-bit EEG/biopotential ADC. Max 24x PGA gain.
+  Channel count is discoverable from the ID register at runtime.
+  Datasheet: https://www.ti.com/product/ADS1299
 
 maintainers:
   - Mike Looijmans <mike.looijmans@topic.nl>
@@ -17,6 +21,7 @@ properties:
   compatible:
     enum:
       - ti,ads1298
+      - ti,ads1299
 
   reg:
     maxItems: 1
@@ -33,8 +38,7 @@ properties:
 
   vref-supply:
     description:
-      Optional reference voltage. If omitted, internal reference is used,
-      which is 2.4V when analog supply is below 4.4V, 4V otherwise.
+      Optional reference voltage. If omitted, internal reference is used.
 
   clocks:
     description: Optional 2.048 MHz external source clock on CLK pin
@@ -75,5 +79,6 @@ examples:
           spi-max-frequency = <20000000>;
           spi-cpha;
         };
+
     };
 ...
-- 
2.51.1

Re: [PATCH v2 1/2] dt-bindings: iio: adc: ti,ads1298: add ADS1299 EEG ADC variants

[Krzysztof Kozlowski]

On 06/07/2026 13:26, Md Shofiqul Islam wrote:
> The ADS1299, ADS1299-4, and ADS1299-6 share the same SPI interface
> and register map as the ADS1298 ECG ADC family but are designed for
> EEG and biopotential measurement.  Key differences from ADS1298:
> - PGA gain up to 24x (vs 12x for ADS1298)
> - Internal reference is always 2.4V (no 4V option)
> 
> Add compatible strings and update the vref-supply description to
> document the ADS1299 reference voltage behaviour.

You already received below comment, so please do not expect us to repeat:

Please use scripts/get_maintainers.pl to get a list of necessary people
and lists to CC. It might happen, that command when run on an older
kernel, gives you outdated entries. Therefore please be sure you base
your patches on recent Linux kernel.

Tools like b4 or scripts/get_maintainer.pl provide you proper list of
people, so fix your workflow. Tools might also fail if you work on some
ancient tree (don't, instead use mainline) or work on fork of kernel
(don't, instead use mainline). Just use b4 and everything should be
fine, although remember about `b4 prep --auto-to-cc` if you added new
patches to the patchset.

You missed at least devicetree list (maybe more), so this won't be
tested by automated tooling. Performing review on untested code might be
a waste of time.

Please kindly resend and include all necessary To/Cc entries.

Best regards,
Krzysztof

[PATCH v2 2/2] iio: adc: ti-ads1298: add ADS1299 EEG ADC family support

[Md Shofiqul Islam]

The ADS1299, ADS1299-4 and ADS1299-6 are 8/4/6-channel, 24-bit
biopotential (EEG) ADCs from Texas Instruments.  They share the same
SPI interface, command set and register map as the ADS1298 ECG family,
making it straightforward to support them in this driver.

Key differences from the ADS1298:
- PGA gain range is 1/2/4/6/8/12/24 (vs 6/1/2/3/4/8/12 for ADS1298)
- Internal voltage reference is always 2.4V (no 4V option)
- Channel count is encoded differently in the ID register: bits [4:3]
  identify the ADS1299 family (both bits set), bits [1:0] encode the
  channel count as (bits + 2) * 2

Detect the chip family in ads1298_init() by checking bits [4:3] of
the ID register.  Store the result in the is_ads1299 flag and use it
to select the correct PGA table in ads1298_get_scale() and to skip
the 4V reference option in the CONFIG3 initialisation.

Signed-off-by: Md Shofiqul Islam <shofiqtest@gmail.com>
---
 drivers/iio/adc/ti-ads1298.c | 84 ++++++++++++++++++++++++++++--------
 1 file changed, 65 insertions(+), 19 deletions(-)

diff --git a/drivers/iio/adc/ti-ads1298.c b/drivers/iio/adc/ti-ads1298.c
index 579200e06cbd6..7cff51d23d12f 100644
--- a/drivers/iio/adc/ti-ads1298.c
+++ b/drivers/iio/adc/ti-ads1298.c
@@ -1,6 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0
-/* TI ADS1298 chip family driver
+/* TI ADS1298/ADS1299 biopotential ADC driver
  * Copyright (C) 2023 - 2024 Topic Embedded Products
+ * Copyright (C) 2026 Md Shofiqul Islam <shofiqtest@gmail.com>
  */
 
 #include <linux/bitfield.h>
@@ -43,6 +44,20 @@
 #define ADS1298_MASK_ID_CHANNELS		GENMASK(2, 0)
 #define ADS1298_ID_FAMILY_ADS129X		0x90
 #define ADS1298_ID_FAMILY_ADS129XR		0xd0
+/*
+ * ADS1299 family is identified by bits [4:3] = 0b11.  Bits [7:5] encode
+ * the silicon revision and vary between production lots, so only bits [4:3]
+ * are checked for family identification.
+ */
+#define ADS1299_MASK_ID_FAMILY			GENMASK(4, 3)
+#define ADS1299_ID_FAMILY_EEG			GENMASK(4, 3)
+/*
+ * ADS1299 channel count is encoded in bits [1:0] of the ID register:
+ * 00 -> 4 channels (ADS1299-4)
+ * 01 -> 6 channels (ADS1299-6)
+ * 10 -> 8 channels (ADS1299)
+ */
+#define ADS1299_MASK_ID_CHANNELS		GENMASK(1, 0)
 
 #define ADS1298_REG_CONFIG1	0x01
 #define ADS1298_MASK_CONFIG1_HR			BIT(7)
@@ -101,6 +116,7 @@
 struct ads1298_private {
 	const struct ads1298_chip_info *chip_info;
 	struct spi_device *spi;
+	bool is_ads1299;
 	struct regulator *reg_avdd;
 	struct regulator *reg_vref;
 	struct clk *clk;
@@ -276,7 +292,10 @@ static int ads1298_set_samp_freq(struct ads1298_private *priv, int val)
 				  cfg);
 }
 
+/* ADS1298 PGA: register bits [6:4] -> gain (000=6, 001=1, 010=2, ...) */
 static const u8 ads1298_pga_settings[] = { 6, 1, 2, 3, 4, 8, 12 };
+/* ADS1299 PGA: register bits [6:4] -> gain (000=1, 001=2, 010=4, ...) */
+static const u8 ads1299_pga_settings[] = { 1, 2, 4, 6, 8, 12, 24 };
 
 static int ads1298_get_scale(struct ads1298_private *priv,
 			     int channel, int *val, int *val2)
@@ -291,12 +310,15 @@ static int ads1298_get_scale(struct ads1298_private *priv,
 			return ret;
 
 		*val = ret / MILLI; /* Convert to millivolts */
+	} else if (priv->is_ads1299) {
+		/* ADS1299 internal reference is always 2.4V */
+		*val = 2400;
 	} else {
 		ret = regmap_read(priv->regmap, ADS1298_REG_CONFIG3, &regval);
 		if (ret)
 			return ret;
 
-		/* Reference in millivolts */
+		/* ADS1298 reference in millivolts: 2.4V or 4V */
 		*val = regval & ADS1298_MASK_CONFIG3_VREF_4V ? 4000 : 2400;
 	}
 
@@ -304,7 +326,8 @@ static int ads1298_get_scale(struct ads1298_private *priv,
 	if (ret)
 		return ret;
 
-	gain = ads1298_pga_settings[FIELD_GET(ADS1298_MASK_CH_PGA, regval)];
+	gain = (priv->is_ads1299 ? ads1299_pga_settings : ads1298_pga_settings)
+		[FIELD_GET(ADS1298_MASK_CH_PGA, regval)];
 	*val /= gain; /* Full scale is VREF / gain */
 
 	*val2 = ADS1298_BITS_PER_SAMPLE - 1; /* Signed, hence the -1 */
@@ -600,20 +623,39 @@ static int ads1298_init(struct iio_dev *indio_dev)
 	if (ret)
 		return ret;
 
-	/* Fill in name and channel count based on what the chip told us */
-	indio_dev->num_channels = 4 + 2 * (val & ADS1298_MASK_ID_CHANNELS);
-	switch (val & ADS1298_MASK_ID_FAMILY) {
-	case ADS1298_ID_FAMILY_ADS129X:
-		suffix = "";
-		break;
-	case ADS1298_ID_FAMILY_ADS129XR:
-		suffix = "r";
-		break;
-	default:
-		return dev_err_probe(dev, -ENODEV, "Unknown ID: 0x%x\n", val);
+	/*
+	 * Detect chip family from the ID register.  The ADS1299 EEG family
+	 * is identified by bits [4:3] = 0b11; the ADS1298 ECG family uses
+	 * bits [7:3] for family identification.
+	 */
+	if (FIELD_GET(ADS1299_MASK_ID_FAMILY, val) == ADS1299_ID_FAMILY_EEG) {
+		/*
+		 * ADS1299 family: channel count from bits [1:0].
+		 * 00 -> 4ch, 01 -> 6ch, 10 -> 8ch.
+		 */
+		priv->is_ads1299 = true;
+		indio_dev->num_channels =
+			(FIELD_GET(ADS1299_MASK_ID_CHANNELS, val) + 2) * 2;
+		indio_dev->name = devm_kasprintf(dev, GFP_KERNEL, "ads1299%s",
+			indio_dev->num_channels == 4 ? "-4" :
+			indio_dev->num_channels == 6 ? "-6" : "");
+	} else {
+		/* ADS1298 family: channel count from bits [2:0], name from family */
+		indio_dev->num_channels = 4 + 2 * (val & ADS1298_MASK_ID_CHANNELS);
+		switch (val & ADS1298_MASK_ID_FAMILY) {
+		case ADS1298_ID_FAMILY_ADS129X:
+			suffix = "";
+			break;
+		case ADS1298_ID_FAMILY_ADS129XR:
+			suffix = "r";
+			break;
+		default:
+			return dev_err_probe(dev, -ENODEV,
+					     "Unknown ID: 0x%x\n", val);
+		}
+		indio_dev->name = devm_kasprintf(dev, GFP_KERNEL, "ads129%u%s",
+						 indio_dev->num_channels, suffix);
 	}
-	indio_dev->name = devm_kasprintf(dev, GFP_KERNEL, "ads129%u%s",
-					 indio_dev->num_channels, suffix);
 	if (!indio_dev->name)
 		return -ENOMEM;
 
@@ -621,8 +663,9 @@ static int ads1298_init(struct iio_dev *indio_dev)
 	if (!priv->reg_vref) {
 		/* Enable internal reference */
 		val |= ADS1298_MASK_CONFIG3_PWR_REFBUF;
-		/* Use 4V VREF when power supply is at least 4.4V */
-		if (regulator_get_voltage(priv->reg_avdd) >= 4400000)
+		/* ADS1298 only: use 4V VREF when supply is at least 4.4V */
+		if (!priv->is_ads1299 &&
+		    regulator_get_voltage(priv->reg_avdd) >= 4400000)
 			val |= ADS1298_MASK_CONFIG3_VREF_4V;
 	}
 	return regmap_write(priv->regmap, ADS1298_REG_CONFIG3, val);
@@ -739,12 +782,14 @@ static int ads1298_probe(struct spi_device *spi)
 
 static const struct spi_device_id ads1298_id[] = {
 	{ "ads1298" },
+	{ "ads1299" },
 	{ }
 };
 MODULE_DEVICE_TABLE(spi, ads1298_id);
 
 static const struct of_device_id ads1298_of_table[] = {
 	{ .compatible = "ti,ads1298" },
+	{ .compatible = "ti,ads1299" },
 	{ }
 };
 MODULE_DEVICE_TABLE(of, ads1298_of_table);
@@ -760,5 +805,6 @@ static struct spi_driver ads1298_driver = {
 module_spi_driver(ads1298_driver);
 
 MODULE_AUTHOR("Mike Looijmans <mike.looijmans@topic.nl>");
-MODULE_DESCRIPTION("TI ADS1298 ADC");
+MODULE_AUTHOR("Md Shofiqul Islam <shofiqtest@gmail.com>");
+MODULE_DESCRIPTION("TI ADS1298/ADS1299 biopotential ADC");
 MODULE_LICENSE("GPL");
-- 
2.51.1