From 308f0338cfae2aa59fb360bfa8f03046ba09fb16 Mon Sep 17 00:00:00 2001
From: Michael Kurz <michi.kurz@gmail.com>
Date: Wed, 21 Apr 2021 00:11:26 +0200
Subject: [PATCH] lpc176x: Add i2c_read functionality

This adds the i2c_read command to the lp176x MCU.

Signed-off-by: Michael Kurz <michi.kurz@gmail.com>
---
 src/lpc176x/i2c.c | 35 ++++++++++++++++++++++++++++++++++-
 1 file changed, 34 insertions(+), 1 deletion(-)

diff --git a/src/lpc176x/i2c.c b/src/lpc176x/i2c.c
index 4d8dc361..7ed631af 100644
--- a/src/lpc176x/i2c.c
+++ b/src/lpc176x/i2c.c
@@ -100,6 +100,20 @@ i2c_send_byte(LPC_I2C_TypeDef *i2c, uint8_t b, uint32_t timeout)
     return i2c->I2STAT;
 }
 
+static uint8_t
+i2c_read_byte(LPC_I2C_TypeDef *i2c, uint32_t timeout, uint8_t remaining)
+{
+  if (remaining == 0)
+      i2c->I2CONCLR = IF_ACK | IF_IRQ;
+  else {
+      i2c->I2CONSET = IF_ACK;
+      i2c->I2CONCLR = IF_IRQ;
+  }
+  i2c_wait(i2c, IF_IRQ, timeout);
+  uint8_t b = i2c->I2DAT;
+  return b;
+}
+
 static void
 i2c_stop(LPC_I2C_TypeDef *i2c, uint32_t timeout)
 {
@@ -125,5 +139,24 @@ void
 i2c_read(struct i2c_config config, uint8_t reg_len, uint8_t *reg
          , uint8_t read_len, uint8_t *read)
 {
-    shutdown("i2c_read not supported on lpc176x");
+    LPC_I2C_TypeDef *i2c = config.i2c;
+    uint32_t timeout = timer_read_time() + timer_from_us(5000);
+    uint8_t addr = config.addr | 0x01;
+
+    if (reg_len != 0) {
+        // write the register
+        i2c_start(i2c, timeout);
+        i2c_send_byte(i2c, config.addr, timeout);
+        while(reg_len--)
+            i2c_send_byte(i2c, *reg++, timeout);
+        i2c_stop(i2c, timeout);
+    }
+    // start/re-start and read data
+    i2c_start(i2c, timeout);
+    i2c_send_byte(i2c, addr, timeout);
+    while(read_len--) {
+        *read = i2c_read_byte(i2c, timeout, read_len);
+        read++;
+    }
+    i2c_stop(i2c, timeout);
 }