From 53f39b99d541754030728d3ce99dc112797dfa38 Mon Sep 17 00:00:00 2001
From: Anton Sarukhanov <code@ant.sr>
Date: Fri, 2 Nov 2018 00:17:03 -0400
Subject: [PATCH] Define ADC register constants, implement register access &
sending commands.
---
ads8698.c | 65 ++++++++++++++++++++++++++++++++---------------
include/ads8698.h | 49 ++++++++++++++++++++++++++++++++---
include/spi.h | 2 +-
measure.c | 3 ++-
spi.c | 6 ++---
5 files changed, 96 insertions(+), 29 deletions(-)
diff --git a/ads8698.c b/ads8698.c
index 0591f2c..ffcc403 100644
--- a/ads8698.c
+++ b/ads8698.c
@@ -1,5 +1,5 @@
/**
- * This file includes functions for interacting with an ADC
+ * This file includes functions for interacting with an ADC.
*
* Written for: TI ADS8698 8-channel ADC
*
@@ -34,42 +34,67 @@ void ADS8698_init(void) {
// Reset the ADC.
ADS8698_reset();
-
- // Start measurements
- ADS8698_send_command(ADS8698_RESET);
- SPI_transmit('H');
- SPI_transmit('e');
- SPI_transmit('l');
- SPI_transmit('l');
- SPI_transmit('o');
- SPI_transmit('!');
}
/* Set the input range on the ADC. */
void ADS8698_set_range(ADS8698_range range) {
- // TODO
- return;
+ uint8_t address;
+ for (uint8_t channel = 0; channel < 8; channel++) {
+ address = 0x05 + channel;
+ ADS8698_write_register(address, range);
+ ADS8698_read_register(address);
+ }
}
-/* Write to a register on the ADC. */
-void ADS8698_write_register(uint8_t address, uint8_t data) {
- // TODO
- return;
+/* Start the ADC's auto-scan mode. */
+void ADS8698_auto_scan(void) {
+ return; // TODO
}
-/* Send a command to the ADC. */
+/* Send a command to the ADC.
+ *
+ * See datasheet section 8.5.1.
+ */
void ADS8698_send_command(ADS8698_command command) {
- // TODO
- return;
+ ADS8698_CS_LOW;
+ SPI_transmit(command); // First byte
+ SPI_transmit(0x00); // Second byte (always zero).
+ ADS8698_CS_HIGH;
+}
+
+/* Write to a register on the ADC.
+ *
+ * See datasheet section 8.5.2.
+ */
+void ADS8698_write_register(uint8_t address, uint8_t data) {
+ ADS8698_CS_LOW;
+ address |= 1UL << 7; // 8th bit signifies "Read/Write Mode"; set 1.
+ SPI_transmit(address);
+ SPI_transmit(data);
+ ADS8698_CS_HIGH;
}
+/* Read from a register on the ADC.
+ *
+ * See datasheet section 8.5.2.
+ */
+uint8_t ADS8698_read_register(uint8_t address) {
+ ADS8698_CS_LOW;
+ address |= 0UL << 7; // 8th bit signifies "Read/Write Mode"; set 0.
+ SPI_transmit(address << 1);
+ uint8_t data = SPI_receive();
+ ADS8698_CS_HIGH;
+ return data;
+}
+
+
/* Reset the ADC.
*
- * Pull RST low for 70ns (instructions: 40-100ns).
* See datasheet section 8.4.1.1.6.
*/
void ADS8698_reset(void) {
PORTC &= ~_BV(PORTC0);
+ // Pull RST low for 70ns (instructions: 40-100ns).
_delay_us(0.47);
PORTC |= _BV(PORTC0);
}
diff --git a/include/ads8698.h b/include/ads8698.h
index 293a92d..b890efd 100644
--- a/include/ads8698.h
+++ b/include/ads8698.h
@@ -1,5 +1,5 @@
/**
- * This file includes functions for interacting with an ADC
+ * This file includes functions for interacting with an ADC.
*
* Written for: TI ADS8698 8-channel ADC
*
@@ -14,7 +14,13 @@
*/
-/* ADC Commands.
+// Macros to toggle control pins
+#define ADS8698_RST_LOW PORTC &= ~_BV(PORTC0)
+#define ADS8698_RST_HIGH PORTC |= _BV(PORTC0)
+#define ADS8698_CS_LOW PORTC &= ~_BV(PORTC1)
+#define ADS8698_CS_HIGH PORTC |= _BV(PORTC1)
+
+/* ADC commands
*
* See datasheet section 8.5.1.
*/
@@ -36,7 +42,36 @@ typedef enum {
} ADS8698_command;
-/* ADC Input Ranges.
+/* ADC program registers
+ *
+ * See datasheet section 8.5.1.
+ */
+typedef enum {
+ // Auto-Scan control
+ ADS8698_AUTO_CH_SEL = 0x01, // Channels to use in auto-scan mode
+ ADS8698_CH_POWER_DN = 0x02, // Channels to shut down
+
+ // Feature selection
+ ADS8698_FEATURE_SEL = 0x03, // Enable & configure device features
+
+ // Range selection
+ ADS8698_CH0_RANGE = 0x05, // Input range for channel 0
+ ADS8698_CH1_RANGE = 0x06, // Input range for channel 1
+ ADS8698_CH2_RANGE = 0x07, // Input range for channel 2
+ ADS8698_CH3_RANGE = 0x08, // Input range for channel 3
+ ADS8698_CH4_RANGE = 0x09, // Input range for channel 4
+ ADS8698_CH5_RANGE = 0x0A, // Input range for channel 5
+ ADS8698_CH6_RANGE = 0x0B, // Input range for channel 6
+ ADS8698_CH7_RANGE = 0x0C, // Input range for channel 7
+
+ // TODO: Implement alarm-related registers.
+
+ // Command read-back (read-only)
+ ADS8698_COMMAND = 0x00, // Current device command (mode of operation)
+} ADS8698_register;
+
+
+/* ADC input ranges
*
* See datasheet section 8.5.2.3.3.
*/
@@ -45,7 +80,7 @@ typedef enum {
ADS8698_RANGE_BIPOLAR_1_25X = 0x01, // 0 +/- 1.25 x Vref
ADS8698_RANGE_BIPOLAR_0_625X = 0x02, // 0 +/- 0.625 x Vref
ADS8698_RANGE_UNIPOLAR_2_5X = 0x05, // 0 + 2.5 x Vref
- ADS8698_RANGE_UNIPOLAR_1_25X = 0x0 // 0 + 1.25 x Vref
+ ADS8698_RANGE_UNIPOLAR_1_25X = 0x06 // 0 + 1.25 x Vref
} ADS8698_range;
@@ -58,5 +93,11 @@ void ADS8698_set_range(ADS8698_range range);
/* Send a command to the ADC. */
void ADS8698_send_command(ADS8698_command command);
+/* Write to a register on the ADC. */
+void ADS8698_write_register(uint8_t address, uint8_t data);
+
+/* Read from a register on the ADC. */
+uint8_t ADS8698_read_register(uint8_t address);
+
/* Reset the ADC. */
void ADS8698_reset(void);
diff --git a/include/spi.h b/include/spi.h
index 5bf901f..f0d0df8 100644
--- a/include/spi.h
+++ b/include/spi.h
@@ -9,4 +9,4 @@ void SPI_init(void);
void SPI_transmit(char data);
/* Receive a byte from the SPI interface. */
-char SPI_receive(void);
+uint8_t SPI_receive(void);
diff --git a/measure.c b/measure.c
index c14a95b..eb61fc1 100644
--- a/measure.c
+++ b/measure.c
@@ -9,7 +9,7 @@
#include "include/ads8698.h"
#include "include/measure.h"
-
+#define MEASURE_RANGE ADS8698_RANGE_UNIPOLAR_1_25X
/* Acquire resistance measurements. */
struct Measurements measure() {
@@ -22,6 +22,7 @@ struct Measurements measure() {
/* Prepare for measuring resistance. */
void Measure_init(void) {
ADS8698_init();
+ ADS8698_set_range(MEASURE_RANGE);
_delay_us(100);
// int sample_count = 2048; // TODO: what is this
// ADS8698_config(&sample_buffer, sample_count, ADS8698_CHANNEL_0, INPUT_RANGE_UNIPOLAR_1_25X_VREF);
diff --git a/spi.c b/spi.c
index e20d0c6..d11b552 100644
--- a/spi.c
+++ b/spi.c
@@ -11,8 +11,8 @@ void SPI_init(void) {
// Set MOSI, SCK, and SS as outputs
DDRB = (1<<DDB3) | (1<<DDB5) | (1<<DDB2);
- // Enable SPI, become master, set clock rate to CPU clock / 16.
- SPCR = (1<<SPE) | (1<<MSTR);
+ // Enable SPI, become master, set SPI clock rate to 1 MHz.
+ SPCR = (1<<SPE) | (1<<MSTR) | (1<<SPR0);
}
/* Send a byte over the SPI interface. */
@@ -26,7 +26,7 @@ void SPI_transmit(char data) {
}
/* Receive a byte from the SPI interface. */
-char SPI_receive(void) {
+uint8_t SPI_receive(void) {
// Wait for reception to complete.
while (!(SPSR & (1<<SPIF)))
;
--
GitLab