AD7280A
AD7280A IIO Lithium Ion Battery Monitoring System.
Supported Devices
Reference Circuits
Evaluation Boards
Description
This is a Linux industrial I/O (Linux Industrial I/O Subsystem) subsystem driver, targeting multi channel serial interface ADCs. The industrial I/O subsystem provides a unified framework for drivers for many different types of converters and sensors using a number of different physical interfaces (i2c, spi, etc). See Linux Industrial I/O Subsystem for more information.
The AD7280A contains all the functions required for general-purpose monitoring of stacked lithium ion batteries as used in hybrid electric vehicles, battery backup applications, and power tools. The part has multiplexed cell voltage and auxiliary ADC measurement channels for up to six cells of battery management. This driver supports the daisy-chain interface allowing up to eight parts to be stacked without the need for individual device isolation.
The driver automatically detects then number of devices present and creates the iio device files accordingly.
Source Code
Status
Files
Function |
File |
|---|---|
driver |
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include |
Example platform device initialization
For compile time configuration, it’s common Linux practice to keep board- and application-specific configuration out of the main driver file, instead putting it into the board support file.
For devices on custom boards, as typical of embedded and SoC-(system-on-chip)
based hardware, Linux uses platform_data to point to board-specific structures
describing devices and how they are connected to the SoC. This can include
available ports, chip variants, preferred modes, default initialization,
additional pin roles, and so on. This shrinks the board-support packages (BSPs)
and minimizes board and application specific #ifdefs in drivers.
Some device parameter may vary between applications and use cases. The
platform_data for the device’s struct device holds this information.
#define AD7280A_ACQ_TIME_400ns 0
#define AD7280A_ACQ_TIME_800ns 1
#define AD7280A_ACQ_TIME_1200ns 2
#define AD7280A_ACQ_TIME_1600ns 3
#define AD7280A_CONV_AVG_DIS 0
#define AD7280A_CONV_AVG_2 1
#define AD7280A_CONV_AVG_4 2
#define AD7280A_CONV_AVG_8 3
#define AD7280A_ALERT_REMOVE_VIN5 (1 << 2)
#define AD7280A_ALERT_REMOVE_VIN4_VIN5 (2 << 2)
#define AD7280A_ALERT_REMOVE_AUX5 (1 << 0)
#define AD7280A_ALERT_REMOVE_AUX4_AUX5 (2 << 0)
struct ad7280_platform_data {
unsigned acquisition_time;
unsigned conversion_averaging;
unsigned chain_last_alert_ignore;
bool thermistor_term_en;
}
Tip
In case platform_data is not present or set to NULL, the driver will use following defaults:
static const struct ad7280_platform_data ad7280_default_pdata = {
.acquisition_time = AD7280A_ACQ_TIME_400ns,
.conversion_averaging = AD7280A_CONV_AVG_DIS,
.thermistor_term_en = true,
};
Unlike PCI or USB devices, SPI devices are not enumerated at the hardware level. Instead, the software must know which devices are connected on each SPI bus segment, and what slave selects these devices are using. For this reason, the kernel code must instantiate SPI devices explicitly. The most common method is to declare the SPI devices by bus number.
This method is appropriate when the SPI bus is a system bus, as in many
embedded systems, wherein each SPI bus has a number which is known in advance.
It is thus possible to pre-declare the SPI devices that inhabit this bus. This
is done with an array of struct spi_board_info, which is registered by
calling spi_register_board_info().
For more information see: Overview of Linux kernel SPI support
Depending on the converter IC used, you may need to set the modalias accordingly, matching your part name. It may also required to adjust max_speed_hz. Please consult the datasheet, for maximum spi clock supported by the device in question.
static struct spi_board_info board_spi_board_info[] __initdata = {
#if defined(CONFIG_AD7280A) || \
defined(CONFIG_AD7280A_MODULE)
{
.modalias = "ad7280a",
.max_speed_hz = 1000000, /* max spi clock (SCK) speed in HZ */
.bus_num = 0,
.chip_select = GPIO_PF10 + MAX_CTRL_CS, /* CS, change it for your board */
.mode = SPI_MODE_1,
.irq = IRQ_PF6
},
#endif
};
static int __init board_init(void)
{
[--snip--]
spi_register_board_info(board_spi_board_info, ARRAY_SIZE(board_spi_board_info));
[--snip--]
return 0;
}
arch_initcall(board_init);
Adding Linux driver support
Configure kernel with make menuconfig (alternatively use make xconfig or
make qconfig)
Note
The AD7280A Driver depends on CONFIG_SPI
Linux Kernel Configuration
Device Drivers --->
[*] Staging drivers --->
<*> Industrial I/O support --->
--- Industrial I/O support
-*- Enable ring buffer support within IIO
-*- Industrial I/O lock free software ring
-*- Enable triggered sampling support
*** Analog to digital converters ***
[--snip--]
<*> Analog Devices AD7280A Lithium Ion Battery Monitoring System
[--snip--]
Hardware configuration
Driver testing
Each and every IIO device, typically a hardware chip, has a device folder under
/sys/bus/iio/devices/iio:deviceX. Where X is the IIO index of the device. Under
every of these directory folders reside a set of files, depending on the
characteristics and features of the hardware device in question. These files
are consistently generalized and documented in the IIO ABI documentation. In
order to determine which IIO deviceX corresponds to which hardware device, the
user can read the name file /sys/bus/iio/devices/iio:deviceX/name. In case
the sequence in which the iio device drivers are loaded/registered is constant,
the numbering is constant and may be known in advance.
root:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
device0 device0:event0
root:/sys/bus/iio/devices> cd device0
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> ls -l
drwxr-xr-x 3 root root 0 Mar 14 11:16 device0:event0
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in-in_scale
-r--r--r-- 1 root root 4096 Mar 14 11:16 in0-in12_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in0-in1_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in0-in1_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in0-in1_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in1-in2_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in1-in2_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in1-in2_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in10-in11_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in10-in11_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in10-in11_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in11-in12_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in11-in12_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in11-in12_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in2-in3_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in2-in3_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in2-in3_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in3-in4_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in3-in4_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in3-in4_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in4-in5_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in4-in5_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in4-in5_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in5-in6_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in5-in6_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in5-in6_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in6-in7_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in6-in7_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in6-in7_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in7-in8_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in7-in8_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in7-in8_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in8-in9_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in8-in9_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in8-in9_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in9-in10_balance_switch_en
-rw-r--r-- 1 root root 4096 Mar 14 11:16 in9-in10_balance_timer
-r--r--r-- 1 root root 4096 Mar 14 11:16 in9-in10_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 name
drwxr-xr-x 2 root root 0 Mar 14 11:16 power
lrwxrwxrwx 1 root root 0 Mar 14 11:16 subsystem -> ../../../../../bus/iio
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp0_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp10_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp11_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp1_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp2_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp3_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp4_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp5_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp6_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp7_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp8_raw
-r--r--r-- 1 root root 4096 Mar 14 11:16 temp9_raw
-rw-r--r-- 1 root root 4096 Mar 14 11:16 temp_scale
-rw-r--r-- 1 root root 4096 Mar 14 11:16 uevent
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0>
Show device name
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat name
ad7280a
Show cell channel scale
Description: scale to be applied to inX-inY_raw in order to obtain the measured voltage in millivolts.
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in-in_scale
0.976000
Show channel 0-1 measurement
Description: Raw unscaled voltage measurement on cell channel in0-in1_raw
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in0-in1_raw
2254
U = in0-in1_raw * in-in_scale + offset = 2254 * 0.976000 + 1000 = 3199.904 mV
Show voltage across all cells measurement
Description: Raw unscaled voltage measurement on all cell channel in0-inX_raw
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in0-in12_raw
27048
U = in0-in1_raw * in-in_scale + (cell_num * offset) = 27048 * 0.976000 + (12 * 1000) = 38398.848 mV
Show auxiliary/temperature channel scale
Description: scale to be applied to tempX_raw in order to obtain the measured voltage in millivolts.
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat temp_scale
1.220000
Show auxiliary/temperature channel measurement
Description: Shows high accuracy band gap temperature sensor temperature in milli degrees Celsius.
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat temp0_raw
2096
U = temp0_raw * temp_scale = 2096 * 1.220000 = 2557.12 mV
Enable cell balance output switch on channel 4-5
The AD7280A has cell balancing interface outputs designed to control external FET transistors to allow discharging of individual cells.
Description: Writing 1 enables the cell balance output switch corresponding to input Y. Writing 0 disables it. If the inY-inZ_balance_timer is set to a none zero value, the corresponding switch will enable for the programmed amount of time, before it automatically disables.
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> echo 1 > in4-in5_balance_switch_en
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in4-in5_balance_switch_en
1
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> echo 0 > in4-in5_balance_switch_en
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in4-in5_balance_switch_en
0
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0>
Enable cell balance timer on channel 4-5
Description: The inY-inZ_balance_timer file allows the user to program individual times for each cell balance output. The AD7280A allows the user to set the timer to a value from 0 minutes to 36.9 minutes. The resolution of the timer is 71.5 sec. The value written is the on-time in milliseconds. When the timer value is set 0, the timer is disabled. The cell balance outputs are controlled only by inY-inZ_balance_switch_en.
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> echo 150000 > in4-in5_balance_timer
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0> cat in4-in5_balance_timer
143000
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0>
Enabling cell and auxiliary/temperature channel threshold events
root:/> cd /sys/bus/iio/devices/
root:/sys/bus/iio/devices> ls
device0 device0:event0
root:/sys/bus/iio/devices> cd device0:event0
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0/device0:event0> ls -l
-r--r--r-- 1 root root 4096 Mar 14 13:37 dev
-rw-r--r-- 1 root root 4096 Mar 14 13:37 in-in_thresh_high_value
-rw-r--r-- 1 root root 4096 Mar 14 13:37 in-in_thresh_low_value
drwxr-xr-x 2 root root 0 Mar 14 13:37 power
lrwxrwxrwx 1 root root 0 Mar 14 13:37 subsystem -> ../../../../../../bus/iio
-rw-r--r-- 1 root root 4096 Mar 14 13:37 temp_thresh_high_value
-rw-r--r-- 1 root root 4096 Mar 14 13:37 temp_thresh_low_value
-rw-r--r-- 1 root root 4096 Mar 14 13:37 uevent
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0/device0:event0>
The AD7280A includes a dynamic alert function that can detect whether the cell voltages or auxiliary ADC inputs exceed an upper or lower limit defined by the user.
Description: Specifies the value of threshold (_high|_low) that the device is comparing against.
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0/device0:event0> echo 2300 > in-in_thresh_low_value
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0/device0:event0> cat in-in_thresh_low_value
2285
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0/device0:event0> echo 4000 > in-in_thresh_high_value
root:/sys/devices/platform/bfin-spi.0/spi0.18/device0/device0:event0> cat in-in_thresh_high_value
3994