Fix compile issues on ESP32

Author: awhitchurch

README.md

@@ -1,11 +1,12 @@
-ProtoCentral AF4490-based Pulse-oximeter shield for Arduino
+ProtoCentral AF4490/AFE4400 based PPG/SpO2/HR shield for Arduino
 ================================
 [![Compile Examples](https://github.com/Protocentral/protocentral-afe4490-arduino/workflows/Compile%20Examples/badge.svg)](https://github.com/Protocentral/protocentral-afe4490-arduino/actions?workflow=Compile+Examples)
 
 [![Oximeter](https://i2.wp.com/protocentral.com/wp-content/uploads/2020/10/4953.jpg?fit=629%2C600&ssl=1)  
 *AFE4490 Pulse Oximeter Shield Kit for Arduino ](https://protocentral.com/product/protocentral-afe4490-pulse-oximeter-shield-for-arduino-v2/)
 
 [![Oximeter](https://i1.wp.com/protocentral.com/wp-content/uploads/2020/10/4949.jpg?fit=689%2C628&ssl=1)  
+
 *Don't have it yet? Buy one here: protocentral-afe4490-pulse-oximeter-breakout-board-kit* ](https://protocentral.com/product/protocentral-afe4490-pulse-oximeter-breakout-board-kit/)
 
 This is the Arduino library for the ProtoCentral afe4490  breakout/shield boards.
@@ -46,11 +47,11 @@ Upload the code to your arduino and open [ProtoCentral-openview](https://github.
 
 ## For the main documentation site, GUI and more resources, please check out our main [GitHub Repo](https://github.com/Protocentral/AFE4490_Oximeter)
 
-
-
 License Information
 ===================
 
+![License](license_mark.svg)
+
 This product is open source! Both, our hardware and software are open source and licensed under the following licenses:
 
 Hardware

license_mark.svg

@@ -17,7 +17,7 @@ const uint8_t uch_spo2_table[184]={ 95, 95, 95, 96, 96, 96, 97, 97, 97, 97, 97,
 
 void spo2_algorithm :: estimate_spo2(uint16_t *pun_ir_buffer, int32_t n_ir_buffer_length, uint16_t *pun_red_buffer, int32_t *pn_spo2, int8_t *pch_spo2_valid, int32_t *pn_heart_rate, int8_t *pch_hr_valid)
 {
-  uint32_t un_ir_mean,un_only_once ;
+  uint32_t un_ir_mean;
   int32_t k, n_i_ratio_count;
   int32_t i, s, m, n_exact_ir_valley_locs_count, n_middle_idx;
   int32_t n_th1, n_npks, n_c_min;
@@ -26,7 +26,7 @@ void spo2_algorithm :: estimate_spo2(uint16_t *pun_ir_buffer, int32_t n_ir_buffe
   int32_t n_y_ac, n_x_ac;
   int32_t n_spo2_calc;
   int32_t n_y_dc_max, n_x_dc_max;
-  int32_t n_y_dc_max_idx, n_x_dc_max_idx;
+  int32_t n_y_dc_max_idx, n_x_dc_max_idx=0;
   int32_t an_ratio[5], n_ratio_average;
   int32_t n_nume, n_denom ;